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Discussion Starter · #1 · (Edited)
I apologize for the lack of formatting. I wrote this on a phone and will add formatting when I can.

I noticed our stickied accuracy threads are getting a wee bit aged. This will also be posted on Airsoft Society, as there’s a lack of this kind of guide. Cue the wall of text.

Airsoft Accuracy

I’ve decided that I’ll start working on creating a little series of writeups related to airsoft accuracy in general, both as a guide for newer players, and as a space to discuss with more experienced techs.

First, let me explain my proficiencies: I’m good at tuning AEGs, specifically M4/V2 replicas. I’m able to explain principles and commonalities that apply to all platforms, but I do not possess the experience to write on the quirks of bolt action and most gas platforms. As such, if anyone wants to write a corresponding series of posts talking about bolt action and/or gas replicas of all kinds, go right ahead!

I will not be posting hearsay. I will be posting based off my personal experiences, physics, and I will also add in content from other techs.

If you disagree, want to share something additional, or simply want to discuss, this is the place for it! Prove me wrong so we can all learn something new. :D I’ll be editing in suggestions as this goes on.

I’ll probably have too many pictures to fit all in this post, so “photo” posts will follow in some cases

Now, let’s get into it:

Accuracy is related to these things in airsoft: barrel, hop unit as a whole, hop packing, air nozzle, fitment and stability (receiver stability included here), cycle timing (for AEGs and HPA), ammo quality and feeding qualities, and then the pneumatic statistics of your gun. Instead of discussing these items individually, I’ll discuss how the systems work together as you increase in knowledge, technical skill, and cost of parts, as one thing affects every other thing. There is no such thing as a “guaranteed list” of parts to make a replica accurate, and if you take the top part recommendations from every parts list and mash them together, chances are they probably won’t work so hot in your replica. Fitment and tolerances are also terrible in airsoft between different manufacturers (and sometimes even the same manufacturer), so you should be prepared to get very good at using your DIY and Dremel skills.

Here’s how it basically works: Your magazine feeds your ammo into the hop chamber. Your nozzle meets your hop rubber and creates a seal, and then your air supply provides an impulse of kinetic energy to begin accelerating the ammo down your barrel. The BB interacts with the hop rubber and acquires backspin, which triggers something called the Magnus effect and gives the BB lift. From there, vibration and stability affect the ammo as it travels down the barrel, propelled and accelerated by the air supply.

The most accurate guns are those that produce the exact same result every time. This means exactitude in the three major elements: ammunition, air supply, and barrel group. All three are important. You can have a gun with an amazing barrel group and an amazingly consistent air supply, but if your ammo is bad quality, then your shots will also be bad.

You should know: because of the way entropy works, distances are a bell curve. A shot at 20 meters is exponentially harder than one at 10 meters. A shot at 70 yards is exponentially harder than one at 60 meters. As the BB travels farther and farther, more and more factors pile up and increase the deviation. It’s like a math problem: get one thing wrong at the beginning and it throws your whole answer off at the end!

In this first post I will be discussing beginner accuracy. The requirements for beginner accuracy are these: must make your rifle accurate enough to hit consistent body shots at 50 meters (may be higher for snipers), while using decent quality ammunition, and must not cost an arm and a leg to implement! At 50 meters of effective range, you are an assault class player who can make the shots he needs to most of the time, and you probably won’t feel outranged by most other AEG players.

If you’re wanting accuracy past 50 meters, that’s coming up.

Beginner accuracy is normal to expect from a decent stock gun, but oftentimes they come from the box, well, not so decent. So let’s talk about how to get your gun to 50.

The first thing you need to do is evaluate how your gun is actually shooting, and to do that, you need two things; a target, and some rubbing alcohol. Turn your hop up off, remove your barrel group from your gun, and clean the barrel using the alcohol and a cleaning rod which probably came with your gun. (YouTube how to remove the barrel group in your individual replica). This will make sure you don’t have any factory gunk or grease inside your barrel or on your hop rubber, either of which will ruin your accuracy.

google how to disassemble your particular replica and hop unit for video

Next, use decent quality BBs (I’ll discuss this below)and take shots at a man size target you either measure or walk off to about 50 meters. It doesn’t have to be exact, and it doesn’t matter what you shoot at as long as you easily hit the target. The list of BBs I think are “good” enough will shrink as the distance discussed gets larger.

If your gun can’t hit the target consistently, you need to evaluate once again.

Get inside your replica. Look at the hop unit, and try and shift it in all directions. If it can move, that will be shimmed out (barrel o-rings, cardboard shims, pieces of cork, aluminum tape—get creative!). If the barrel is loose in the upper receiver, you can wrap it with tape (Teflon tape, scotch tape), both of which I will discuss.

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Here’s a Prowin hop unit fitted to the gearbox of an M4 replica using cork. I prefer cork because it tends to compress only as much as it needs to in order to provide good pressure

Next, take a look at your hop arm, the thing that moves whenever you adjust your hop, and applies pressure downwards into your hop rubber. If it can wiggle, we’ll shim that out using either plastic/aluminum shims (soda can) or tape (Teflon/aluminum).

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Here’s the hop arm from my Arcturus NY06 build. Two pieces of thin plastic have been glued to the sides in order to provide a tight fit. The nub has also been glued to the arm

Take your hop unit off the barrel, being sure to turn the hop off and remove your arm/nub before doing so.

Look at your hop rubber after you carefully remove it from the barrel. It should feel grippy in your fingers, and shouldn’t have oil or grease on it, especially inside. (Outside can be okay in small quantities, but I’ll talk about that later) If it’s not grippy, or if it feels slick/hard, that means it’s due for replacement, which we’ll talk about here in a second.

Check your nub and hop arm—they should feel stable and sturdy, and the nub should stay centered on the arm. (Your hop unit may not have some of these parts, but the principles apply) I usually glue the nub to the hop arm to ensure centering, even if it seems fine (superglue)

After that, make sure the hop unit is tight on the barrel. If not, we’ll shim the barrel with tape to fit.

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this is a Lambda barrel and G&G hop unit. You can see how the barrel has pieces of scotch tape wrapped around it to ensure a tight fit

Finally, look down your barrel. Assuming you’ve already cleaned it, there should be no residues, gross crap, or bad finishing—it should be shiny and straight. If it’s not so shiny, you’ll want to polish it (I’ll discuss this later), and if it’s not straight, replacement is the best option.

That covers the barrel assembly evaluation. Next, look at your nozzle. If it appears damaged at all, or if it wobbles a lot you may want to consider replacement. Place a BB on top and see how it sits—if it’s uneven, it may affect accuracy.

For beginner accuracy, we won’t cover inside gearboxes or compression assemblies. Issues outside of the barrel group can cause issues for sure, but for 50 meters, most guns are fine enough out of the box.

Now, aside from stabilizing and polishing, here’s how you can improve your accuracy and the potential replacements you may need in full detail. Keep in mind, this is for achieving accuracy with a minimum of 50 meters—we’re not shooting for 100 meters right away, and my parts and mods recommendations will become much more refined as we get to higher accuracy levels.

First is good quality ammo. Your gun will not shoot well with low quality. Heavier is better, and offers more range and accuracy, but for assault class weapons I find .25g to be sufficient for most of my needs. Go heavier as your budget allows and as your intuition tells you, but be aware that many hop setups aren’t capable of lifting super heavy BBs. (I’ll discuss this more down below) Here are some brands I have found to provide consistent shooting:

G&G is my go to. I use their .25g and their .30g, and I have never had a stray BB with their ammo.

Valken Accelerate is my “run of the mill” ammo choice. If you can’t get higher quality, this ammo will work. I have made some very long range shots using Valken .32g, but I can’t recommend it over G&G.

I like Bioshot, but not for the price. G&G is better.

Do not use Lancer Tactical or Elite Force. They’ll shoot, they probably won’t break your gun, but they’re really not suitable for outdoors shooting.

BLS has been known to have some inconsistencies in their ammo—I’ve been hearing that they sometimes package extra ammo from their OEM runs and sell it as their own, giving inconsistent performance. For this reason I cannot recommend them.

I’m currently testing Bushido and I’ll upgrade once I know more.

Hop packing/rubber. This is the single most important piece of your replica when it comes to accuracy, as it’s the part that has the most important contact with the BB. You can often get away with using a stock barrel, hop unit, nozzle, etc, just change your hop rubber and get excellent accuracy. If you check yours and find it oily or greasy in any way, clean it well with alcohol and try it again. Since the hop rubber uses friction to apply backspin to your BBs, it should never come into contact with any oil or grease. This extends to all replicas, which is why Green Gas with silicone oil in it is such a dumb idea.

Hop rubber principles. Folks will debate up and down over whether hard or soft rubbers are better, and which are the absolute best. We will talk about some of that later, but for now, there are many rubbers that can get you to 50 meters without trouble. I find soft hop rubbers are better in basic setups.

For distances of 50 meters, here’s the rubbers I recommend IF you need to replace:

Krytac Orange and Blue—preferably Orange. These are split mound rubbers that are very easily tuned, making them ideal for newer techs. You can use your stock nub and hop arm. A well tuned setup can take you past 50 meters with ease.

PDI W-Hold. This is another split hop rubber, but I’ve found it even more accurate than the Krytac, and very easy to install and tune using stock nubs. This is a rubber that can take you well further than 50 meters.

G&G Green and Blue. The green is extremely similar to standard hop rubbers, and the blue is a split mound like the others. These are basic upgrades and are commonly used and easy to tune. They may require slight sanding of the feed lips for proper feeding.

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an Arcturus stock rubber, Krytac blue, and G&G blue side by side. All three are more effective than typical stock rubbers, but the Arcturus has been the least effective in my experience, I think because of the reduced contact area relative to the other rubbers

There are many others that will work here, and I would love if other techs would recommend their favorites for me to add!

Hop rubber modifications

If your hop rubber feeds great and feel grippy to you, but still doesn’t give you good accuracy, here are some things you can do to keep your hop rubber while still increasing your accuracy:

The Pseudo-Flathop mod. As far as I’m aware, I’m the only one who has done this exact combination, but the principles are common.

Here’s what you’ll need: Your stock hop rubber, a dremel or cheap cordless drill with a sanding bit, some 8mm (approximate) vinyl tubing, superglue, and that’s it!

Here’s how to do it:

Take your stock hop rubber. Turn it inside out carefully. This can be a pain, but do it gently and you’ll be fine.

Next, stick it on your barrel inside out, and then use your dremel or drill to carefully sand off the contact mound and the little alignment mound so the rubber is completely flat.

Now, turn your rubber back the right way. Put it on your barrel like normal, but turn it 45 degrees, so the two sanded areas are on either side of the barrel, and a fresh piece of rubber sits in the how window, which is the hole in your barrel.

Now, take your hop arm and stock nub. The stock nub is probably a little cylinder. Cut it in half so it’s flat and glue it to your hop arm, and carefully use your dremel (a round jewelry file also works here) to make it slightly concave in the same direction the barrel goes.

Put your hop unit back on your barrel and over your hop rubber.

Now, take your vinyl tubing. What you need to do is cut a little patch the same approximate size as the hop window in your hop unit (the place you can see the hop rubber through). The patch should sit extremely flat on top of the hop rubber.

And finally, glue the patch to your modified hop nub/arm with superglue, and then reassemble your unit, making sure everything is very straight and stable!

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this is a finished pseudo flat hop. Notice the wide slightly concave contact patch—this mod produces a very similar result to lauded rubbers like the Maple Leaf MR.Hop without the fitment issues that will be discussed later in the series

Barrels. Most often your stock barrel is fine, and with a little polishing can work great, but there are cases where the barrel isn’t straight, or has finishing issues that can’t be polished out. Sometimes, even though the barrel looks fine, it’s just not good and limits your accuracy because of some unseen flaw.

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This is a stock G&G aluminum barrel from an old CM16, and is a great example of a “bad” barrel. Notice the close up photo: the inside of the barrel looks exactly the same! This barrel provided horrible accuracy, and replacing with a Krytac 387mm was like night and day

Here are basic barrel principles. Any normal barrel length can be accurate, even down to 100mm, but barrels themselves do not become more accurate after 300mm. Basically, if the BB has enough time in the barrel to stabilize, it doesn’t matter how much extra barrel you have. I’ll go into voluming in later installments, but for the target of 50 meters, you can usually ignore it. As for inner diameter, some would say only 6.01mm, some would say 6.05mm and above, and some would say in between. Having used barrels from 6.01mm to 6.08mm, here’s my take: my wider bore 6.08mm is a hair more accurate than my tighter bore barrels… but it’s really not by much. Bore consistency and finish quality matter much more, in my opinion, than the diameter (as long as your BBs are correctly sized and fit in your barrel). For anything under 75 meters, I would use the barrel with the highest quality available in order to squeeze the most accuracy.

With that in mind, most AEGs work great with barrels in between 250mm and 430mm, and here are some of the barrels I’ve found to work really well. (As always, y’all add your recommendations!)

Krytac. If a barrel is bad, you can use a Krytac stock barrel as an “upgrade” as these are just fine. For the money ($5 on Umbrella Armory at the time of this writing) they are far and away the best bang for your buck in terms of barrel replacement that I’ve used. 6.05mm

G&P. Similar rules as Krytac, but it costs more than $15, it’s probably not worth going for specifically. 6.05mm

ZCI. These work fine. About the same as a Krytac or G&P though, so not worth paying more for unless you need an FPS boost or like having a steel barrel.

Lambda. Lambda is essentially the same quality as PDI without the huge price tag. Their SMART series is very affordably priced compared to many other “top” barrels and performs very well. If you plan on spending more than $20-30 on a barrel, Lambda is my go-to.

I would not buy:

Prometheus. Prommy is fine, just not better than Lambda, and not worth dealing with the chance of fakes (which are not good), as well as the high price tag.

PDI. They’re good, no questions asked, but at what cost? Lots of money, that’s what.

Angel Custom. Some folks like to do special stuff to these like lap them to make them good (special kind of polishing), but don’t buy one to actually use it unmodified.

And that wraps up barrel replacements.

Finally we have hop units, which I haven’t mentioned until now. Most AEG hop units are actually just fine, and can be easily stabilized to perform just as well as an expensive unit. Aluminum hop units are not better than polymer ones, and some techs (including me) actually prefer polymer as it’s easier to modify if you should ever need to.

That being said, hop units can occasionally be faulty or just plain bad. It happens. Here are some V2/M4 hop unit recommendations for replacement. (Someone help me fill out for other replicas and systems!)

For M4/V2 hop units, here’s the general rule: original hop units can be just as good as newer rotary units, but if the wheels are loose and wobbly, you may want to upgrade to a rotary unit, which tend to be a lot more solid.

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Here we have three M4/V2 hop units. At the top is an SHS traditional/original style, removed because it didn’t fit in a modern receiver set. In the middle is a Dytac Prowin copy that I was messing with. Finally is a G&G rotary, waiting for my next build.

G&G Rotary. I really like this unit. They fit solidly on every barrel I’ve tried and provide consistent pressure. You can also get them cheaply if you keep an eye out. After having amazing success with my test buy, I purchased two from Umbrella Armory for $9 each.

Prowin. Some folks love these and some folks hate them. Whatever the opinions say, don’t get the clones. I’ve had good success using an original unit, but the Dytac clones I’ve used have been not good.

Arcturus. It’s another polymer hop unit. Works great. Maybe not quite as solid as the G&G, but nothing wrong with it.

Krytac. These are a little weird compared to ordinary units, but work great nonetheless.

Valken. I actually like their rotary hop unit. It’s ordinary but it works, and you can get them for pretty cheap. (If someone knows who OEMs these let me know)

Here’s what I would not buy:

Maxx. Maxx units have a complicated story. Some of the models have issues, and some techs love the features these offer, but what it ultimately boils down to is this: they hop BBs the same as all the other units, and they cost $80-90. Some people love these, but I just can’t justify them for myself.

And that about wraps it up for this first section.

One thing. You’ll note I didn’t mention FPS at all. This is because FPS is not one of the primary factors determining accuracy. Guns shooting low FPS can still be accurate, and guns shooting high FPS can be inaccurate. In general, the benefit behind having higher FPS is having more forward momentum behind your BB, but air resistance increases exponentially over speed, meaning that you get exponentially less range for every FPS you add. I.e. a BB traveling at 200 FPS can travel 80% the distance of the same BB traveling at 400 FPS. The real advantages to high FPS is not getting to your targets faster, or traveling a huge difference farther (they do travel farther) but actually punching through wind and general air interference.

The other advantage is that higher FPS guns can impart more energy to heavy BBs, which are able to more effectively use the higher energies. Because air resistance increases exponentially like this, heavier BBs are more effective than lighter BBs. The heavier your ammo, the less wind will be able to affect it, the less variation the BBs will have, and the more momentum and backspin the BBs will carry with them. For 50 meters, .25g will serve you well if the wind conditions are normal.

I’ll post a video of constructing and deconstructing hop setups to evaluate as well as how to put together my “pseudo flat hop” mod whenever I can.


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319 Posts
Discussion Starter · #2 · (Edited)
Airsoft Accuracy Intermediate

I realized I forgot to take some of the pictures I needed before going out of town, and I figured it was better to post this for review than to hold up for a few pics

This next section will cover accuracy from 60 to 70 meters. Please note that many of the suggestions from the previous post will get you to 60-70 in conjunction with proper ammunition, but are in no way guaranteed, and subject to fitment and installation, as well as what you have on your stock gun. Some of the suggestions from this post may also get you farther than 70 meters, but again, this is airsoft; results will vary.

For everything in the beginner category you can pretty much just pick up and do it. This section is a little more involved, and requires you to have basic knowledge of your gearbox. Everything not mentioned here can easily be googled.

Topics discussed: FPS (finally, yes). Air seal inside the gearbox and between nozzle and packing. BB placement. Nozzles and replacements. Flat/concave “modern” rubbers and Maple Leaf rubbers. “Modern” barrels. Voluming, and finally, designing systems.

RHop is coming, but that will likely be the next post, as I believe RHops (especially when DIYed) count as advanced mods/upgrades and aren’t suitable for most over the slew of other choices.

First up, assuming you’ve worked through some of the earlier mods and replacements (skip steps as needed), you need to reevaluate your rifle.

Here are some basic items that may prevent your gun from reaching:

Your barrel is too long. Yes, long barrels actually reduce accuracy, most often because of two reasons; long barrels are much harder to keep straight and consistent, and the big one: most guns realistically don’t have enough air in them to fire anything but a .20g out of, say, a 509mm barrel, even with a full cylinder. The gun will still shoot, just maybe not accurately.

You have a very weak spring. If your gun shoots under 300, you can absolutely reach 60 meters, but the wind has more time to affect your BB, and can do it more easily. This reduces your practical accuracy.

Now, onto the regular stuff.

If your airsoft gun can’t make it to 60-70 meters (whichever you’re going for), you may need:

Heavier ammunition. 60 meters is near the limit of .25g BB in my opinion, without using so much overhop that you can’t hit close targets too. For consistent shots at these distances I recommend .28g to .32g, with .30g being my favorite. G&G is once again my top recommendation. Obviously you can go heavier, but I’m assuming we’re still shooting at normal outdoor FPS levels here. (I’ll talk more about this later)

Decent FPS consistency. Think about it: hop rubbers work by friction, friction is related to speed, and that combination affects where your BB lands, typically showing in the up-down consistency of your shots. For these ranges, you don’t need amazing FPS consistency, but getting it to within +/- 4 FPS will help make your groupings tighter. For my guns, I like to tune to +/- 1 FPS, as it’s a relatively easy way to get more accuracy out of your gun. That being said, if your gun jumps 15-30 FPS or more, it’ll be an issue, and you probably won’t be hitting targets at range very easily.

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I’ve had people tell me it was next to impossible to get ~1 FPS variance on an AEG due to the design. Here it is at almost 30 RPS. This is consistent enough for a tuned bolt action… I changed one part.

A more efficient hop. Some of the rubbers I talked about in the first post will get you to these accuracy ranges, but I will be removing a couple from the list, as well as adding a couple.

A well designed nozzle with the right length and little to no wobble. This will help place your BB in the same spot every time. Many stock guns already have this, but others may not.

You may also need to change your voluming, adjust your piston in a couple of ways, or change your spring, all of which I will discuss.

The first things you’ll want to adjust are your hop rubber and your ammunition, and this holds true for basically all replicas.

A hop rubber that allows for wider more general contact with the BB can provide more efficient hop, as well as more consistent accuracy and the ability to lift much heavier BBs. They can also be harder to tune, require a special nub or a modified nub, and I find they tend to have more fitment issues than “traditional” or “split mound” style packings.

Here are a few I’ve found to be effective, and my caveats on them:

PDI W-Hold. I’ve found this rubber so far to be very effective hopping up to .30g (the max I’ve tried), and maintaining accuracy to past 60 meters even with .25g. I have yet to fully experiment with tuning this rubber, and I’ll add more notes as I do more with it.

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Here’s a ML MR.Hop combined with the UA G&G RHop arm and a G&G rotary. Note the consistent, concave hop surface

Maple Leaf rubbers (specifically the MR.Hop). These rubbers are extremely accurate and consistent… when tuned properly. You can use them with any BB weight, and they work fine in full auto, making them superior to RHop (in my opinion, for many builds) The contact surface is huge, and when combined with a flat or concave nub (don’t use the ML Omega nub. Get a wide one or make your own), the accuracy is very, very good. These have been cited to get 95% of the results from RHop without the RHop issues, and I have to agree. But, I have a few issues with these rubbers, otherwise these would be my absolute go-to. My negative comments here are for the AEG version, not GBB versions, etc. I’ve never owned those and can’t comment. I’ll share a picture of this below, but the ML rubbers have some different dimensions than most. First off, the contact patches are super wide, which is awesome, but they also may not fit your barrel window. This isn’t a true negative, more of a caveat. The packing is also very thick at the front with long lips. The lips can be slightly sanded to help out, but because the front of the packing is so thick, they don’t fit correctly in many hop units. In fact, the only hop unit I’ve found that it’s a drop in fit for is the G&G Rotary. (If y’all know of other units that provide drop in fit, let me know!!) The issue with the front of the packing being so thick is that it pushes both the contact patch and the barrel itself backwards in the hop unit, making it so you can’t put the clip on, and you need a nonstandard nozzle length to work correctly with the setup. I’ve spent the time to make it work with one replica, and the results are great, it was just a pain to set up, and you cannot use full auto thanks to the barrel and nozzle being pushed farther back than normal.

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Here’s a TR-hop setup. This is turned on fully to demonstrate the contact patch, but you can see how thick the patch is.

TNT TR-hop. I want to love this rubber, but the issue is that my BB choices aren’t heavy enough! If you’re wanting to use .40g etc, this may be a good choice for you (hops .30g to the sky on zero hop).

Flathop rubbers. Get a wide nub or make your own. I like making my own personally. It alleviates credit card stress from paying $10 for a minuscule spec of plastic or rubber. It’s worth noting that you can flathop any rubber (same process as preparing the rubber for my pseudo flathop mod), but not all rubbers are suitable. Flathops can grant great results, but can be tricky to tune.

Pseudo flathop. This mod can absolutely take you to 65-70 yards. If it doesn’t, you either need a different rubber, or you did it a little bit wrong (precision is key).

All that being said, here’s the cheese: if ML MR.Hop rubbers fit in your hop unit… these are pretty much the top choice.

Rubber hardness. The advantages of harder rubbers are more durability and resistance to tearing. I’ve never torn even a 50 degree rubber, and I’m okay with replacing after a crap ton of rounds, so I’d say go softer when possible for more grip. It’s worth noting that silicone packings have way more grip than rubber packings, so you can get away with using super high degree silicone packings without sacrificing grip/air seal. For example, I use a ML MR.Hop silicone 85 degree that has just as much grip and seal as a 50 degree regular rubber.

Let’s get into the nitty gritty bits: voluming and system design. In the previous post, covering how to get your gun past 50 meters, none of the suggestions or recommendations affected the role your replica allows you to play, instead focusing more on optimizing your current system. Now we’ll talk about specializing your system. To give an example, an AEG with a piston weighing 35g and an air brake piston head really shouldn’t be paired with a speed motor, 13:1 gears, and an RHopped 150mm inner barrel. Not if you want your gun to function optimally.

Let’s break it down. Without heavy ammunition, there is a hard cap on range. We can still make our replicas very very consistent, but eventually you reach a hard cap where the BB simply can’t retain any more backspin, and there your range runs out. So how do we lift heavy ammunition more effectively? The answers are simple in concept; you need enough air to properly accelerate the BB, a barrel that’s around the right length to give good efficiency, and a piston with the right weight to put energy into the BB.

Heavier BBs accelerate slower, and require more air to accelerate to full velocity. Think of accelerating a semi vs. a sports car, and how much energy it takes. What’s also interesting is that heavier BBs get more energy from shorter barrels, since they exit the barrel slower. This means that, sometimes, to get maximum efficiency you may want to use a barrel of 350mm or shorter in your “DMR”.

Most stock guns I find are either correctly volumed or a bit over volumed for .25g, with an example being the Krytac Trident SPR (very common one at my field), which has a 3/4 cylinder and a 387mm inner. However, if you want to shoot heavy BBs, you’ll usually find yourself losing FPS/joules unless you change your cylinder or barrel. So, to reach the same power you end up needing a heavier spring, which is almost always a detriment to durability. The exception to the rule is usually short guns, where manufacturers combine short barrels with ordinary cylinders to create that “pop” of extra air leaving the barrel. Because of that extra air, if you put, say, a 400mm barrel on a G&G ARP9, you can easily get over 415 FPS.

How to get the right volume for your build? First, to clear away any confusion, while I believe that over voluming and under voluming can definitely affect accuracy, I think that if you’re vaguely in the ballpark you’ll have very similar accuracy to a replica with “perfect voluming”. The main advantage of perfectish voluming is silence, as you will remove most of the barrel pop that occurs when you shoot.

I won’t go into full detail about voluming here, as there’s already an excellent write up by 1Tonne stickied here on this forum.

Now that you have a vague idea of what weight BB goes with what barrel, let’s talk cylinders and barrels. (I’ll speak in terms of AEG cylinders, but the principles apply for all replicas)

For heavy BBs It’s my opinion that you will almost always want to use a full cylinder. Using a full cylinder allows you to get higher efficiency, and if you’re lifting heavy BBs, you really shouldn’t have a crazy long barrel, so it’s not an inconvenience either. (You can calculate for different kinds of cylinders via 1Tonne’s ratios to get in the ballpark)

Well which cylinder?

I’m not picky. I do happen to dislike aluminum though. I prefer steel or brass, and as long as it’s on spec and seals well with my piston head/cylinder head than I have no issues. Polish these bad boys up though. The shinier the better. Some folks like Maxx (a bit expensive) some like Guarder, but I’ve never heard of any good reason why not to use a regular old $10 steel cylinder as long as it’s on spec.

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Here is a brand new Guarder Chromium cylinder waiting for when I want to give a build a little extra TLC. Chances are the difference between this cylinder and an ordinary steel one is only a few %, but it does look nice!

Well what barrel?

At this point I won’t cut any of the barrels out of the previous list just yet. Remember that your voluming does not need to be exact, and you can go over or under by quite a bit depending on the bore diameter. This is an exercise in efficiency and not necessarily in accuracy (necessarily). The one caveat is that you’ll want to be extra good about your polishing (which really isn’t hard). The only barrel that’s getting close to being cut out are the ZCI barrels. I’ll be reworking my ZCI barrel group soon (paired with a Krytac build), and my opinion may change, but I’ve not seen these perform well over 60-65 meters, most likely due to slight inferiority in bore consistency, finishing quality, and possibly related to it being a 6.02mm, though at this range I haven’t ruled out tighter bores yet.

I will add a couple more barrels to my list of recommendations. These are more expensive, and offer diminishing returns, but they may be worth it for you.

T.N.T. S+. I picked one of these up from Guges… and it really does perform. Paired with a ML 60 degree MR.Hop, custom nub and PDI 170% spring, I can send .25s past 65 meters with good conditions. With .30g that increases to past 70, all while keeping it under 400 FPS w/ .20g. The finishing is really nice on these, and they work similarly to ML crazy jet barrels, with an “expansion chamber” at the end of the barrel to hopefully “smooth out” the air around the BB. The price tag is not incredibly nice though. This is one of, if not the most expensive barrel I’ve used. Edgi and other lapped barrels may make it onto this list in the final installment, but this is the most expensive I’ve personally used.

I’m hearing recommendations for DaVinci barrels. The story is that Lambda was founded by folks who left PDI, and DaVinci was founded by folks who left Lambda. I’ve never tried one myself, but I’m hearing they’re even slightly above Lambda in terms of quality, though they may be harder to find and more expensive.

Here is the stock barrel from my Novritsch SSP1, freshly polished to a near-mirror finish, although it’s difficult to see in the photo

Let’s talk about compression assemblies. We’ve gone through cylinders and barrels, now let’s talk about cylinder heads, nozzles, and pistons.

Almost every cylinder head can be made to work. Sometimes cylinders are off spec so badly that they’re actually too small for an ordinary cylinder head, or the nozzle tube is badly off spec, but this would be unusual. Here’s how to properly test your cylinder head:

With your cylinder head still installed in the cylinder, take the nozzle off and put your thumb over the nozzle tube. Now, push your piston assembly into the cylinder. (YouTube for a visual representation) You should feel strong resistance, with no hissing. If you hear hissing, there’s most likely a leak around the cylinder head o-ring, or the nozzle tube. If you’re not getting a seal but don’t really hear hissing, this is most likely related to your piston assembly. I’ll cover this later.

Inspect the cylinder head o-ring/s. Make sure they’re in good condition, and lightly greased. If they’re damaged or bad, go to your local hardware store and get a replacement (bring the CH with you to test fitment) or order a new ring,

Next, hold the cylinder head in one hand and wiggle the nozzle tube in the other: if it wiggles this is bad. You can try and DIY to fix nozzle tube wiggle/seal issues, but I find it’s easier to simply replace at that point.

Now, here’s how to make your cylinder head awesome (you can do this to almost every cylinder head in existence):

Wrap Teflon tape around the o-rings. This is incredibly simple and would save so many people money if they did it.

If you still have trouble with seal between the cylinder head and cylinder, smear a tiny bit of silicone sealant around the rings when you install, making sure everything is seated 100% even and correctly!

Hand Automotive tire Tire Finger Thumb

Here’s a pic of a reworked plastic cylinder head sporting two mods: Teflon tape, and the silicone buffer mod, which I’ll discuss later

In case your cylinder head has a wobbly nozzle, doesn’t seat correctly, or breaks in half for some reason, here are some halfways decent replacement option:




Krytac, purchased from Umbrella Armory.

Most of them, really. I prefer plastic over aluminum personally (easier to modify, quieter), but aluminum, brass or steel are just fine.

Here are what you should not buy:

“Silent” cylinder heads. (Not actually quieter)

Anything with a rubber buffer on the front. These can break your cylinder head pins.

Anything that costs more than $10-12 or so. I know things cost different amounts depending on where you live, but this is an item where you can go cheap and be fine.

Now, onto piston assemblies. This will get a little more complicated.

Your piston assembly is one of the most essential parts of your build, since it’s what transfers the kinetic energy from the gears to the spring, transfers the energy from the spring to the air in your cylinder. You can have an amazing build everywhere else, but if your piston assembly is useless, then your gun will also be useless.

Piston assembly misconceptions:

You do not need bearings on your piston. It’s fine to leave them on if you don’t care about the weight, but they’re almost useless.

Just because something says “upgrade” or “awesomeness” does not mean it is. So many crap pistons are marketed as amazing.

Never buy prebuilt piston assemblies unless you feel like wasting your money. They’re not better than what you can easily put together yourself.

More expensive is not the route to success. The SHS blue is one of the most popular upgrade pistons in existence and they only cost a few bucks if you buy from aliexpress.

missing pic

here’s a pic of a ruined SystemA Supercore piston. The teeth stripped rather quickly—maybe an M170 wasn’t the best idea here…

Hand Guitar accessory Gesture Finger Musical instrument accessory

here’s a pic of an Arcturus NY06 stock piston. This thing is ridiculously strong. Aside from the heavy weight, I’d want one of these in every build.

Here’s how to evaluate your piston assembly:

Test for air seal with the cylinder. If it doesn’t seal, you may need to do a couple mods, replace the o-ring, or even the piston head itself.

Put the ring over your cylinder and gently heat with a lighter to try and expand it a bit.

Regrease the ring.

If you can’t seem to make the piston head work, here are some decent replacements:

SHS POM (can be picky about what cylinders it likes, be warned).

Lonex POM (great).

Krytac stock (these work).

Angel Custom Polycarbonate (I hate Angel Custom, but this one does work fine, and saves you a few bucks and a gram of weight over the Lonex it’s a clone of).

Look at your piston itself. Does it look or feel flimsy? Is there solid material behind the teeth? Is there excessive wear or stripping on it? How many metal teeth are there?

Most stock guns have pistons that are appropriate for their FPS, but some are trash out of the box. If you intend on increasing ROF or spring power any, intend on replacing your piston and be happy if you don’t have to.

If it feels like trash, it probably is. Replace!

If there are gaps behind the teeth, or it looks like the pickup tooth is floating on nothing, replace!

If it looks ruined, replace!

Check how loose any metal rack may be.

If everything looks solid but there are gaps between the rack and the body or the rack is loose, epoxy that sucker!

If you feel like it’s weak in any way around the rack, epoxy that sucker!

If you feel annoyed at it, epoxy that sucker!

Weigh your piston on a gram scale if you can. For accuracy builds, I prefer a piston weight of 28-30 grams. If your ROF is 20 or over, though, you may need to go light (20 or lighter) but this is not the guide for that.

missing pic, lol

here’s an SHS 14T lightened piston. I’ve corrected the AOE and epoxied the rack and it’s held up great at up to 35 RPS/410 FPS

You usually want at least a few metal teeth on the release side of the piston, but I prefer FSR (full steel rack) pistons. That being said, there are some notable standouts. Here are some good aftermarket piston replacements, and some chunky stock pistons that can put in work for you:

Arcturus. If you find it, it weighs 22 grams by itself, and is an absolute beefcake. I’m running mine lightened at 29 RPS with zero issues.

Krytac. These are fine. Would not recommend for past 20 RPS though.

SHS blue. Some folks say don’t get the version with the rectangular slots, but mine has been just fine after I prepped it correctly. That being said, I wouldn’t go higher than 40 RPS on this version—go for the one with round holes.

Lonex red. Chunky.

Now for the fun part.

Nozzles are one of the trickiest parts of a build in my experience. They are also a critical part of your system, given that they are what directly seat your BB in your hop packing. It is extremely important that your nozzle has as little wiggle as possible, seals properly to the hop packing, and seats the BB evenly every time. A bad nozzle can cause feeding issues, FPS issues, and even jams that can destroy your gearbox.

*I’ll add pics of nozzles later

Nozzle misconceptions:

Nozzles with no o-rings are just fine. Rings originated to support the nozzle and prevent wiggle. You do not need them, and in many cases rings make your nozzle extra wobbly. Example: Krytac (no oring). Air pressure flows in one direction, so air never ‘wants’ to flow backwards between the nozzle tube and nozzle wall.

Metal nozzles are not better than plastic. I prefer plastic in most cases as they are easier to modify. Nothing wrong with metal, they’re just not better.

Many stock nozzles are just fine, and should not be replaced. Nozzle length can be the difference between perfection and jamming, and so I try and keep stock nozzles on all my builds—they typically fit correctly, unlike many aftermarket units.

That being said, if your nozzle is damaged, doesn’t like your packing, or is warped/off spec, here are some replacement options:

I prefer nozzles with cutouts and light crowning as I find they offer more consistent shots.




Maxx. The different lengths are useful, but I would go for the adjustable in almost all cases. The adjustable is an incredibly good tech tool to fine-tune your build.


Plastic stock nozzles that you can find around.

Here’s my favorite nozzle fitting procedure if the stock nozzle doesn’t work: put in a Maxx adjustable, find the best combo of air seal and fitment, and then take a plastic nozzle and modify it to copy perfect length and BB seating.

Wood Lipstick Writing implement Material property Cosmetics

Here’s a pic of a Maxx adjustable next to a Lancer stock nozzle. The Lancer wasn’t feeding correctly after I changed the packing, so I had to refit the nozzle—notice how the BB is seated exactly where the Maxx seats it.

FPS and springs.

In general I try not to go high FPS even on “highly accurized” builds, as it limits my play style. I’m okay with giving up a few meters of range for the ability to have a 20 foot MED. it also puts a lot more stress on your gun and for many replicas necessitates other upgrades and mods to withstand the increased power.

However, here are some general rules for when to increase your spring power from an accuracy standpoint:

If your BBs are still flying perfectly straight when they hit the ground—you want your gun’s maximum range to exceed your effective range. Ideally they’d be exactly the same, but since that’s crazy precise, keeping maximum range above effective is a good way to make sure you get the most out of your effective range.

If the wind is your worst enemy.

If you’re using heavier BBs and feel like they’re flying badly for no reason.

For snipers, your starting point in joules is probably way higher, but since this accuracy guide is for all players, this section is indeed focused on AEG performance.

For consistent FPS, you need a good spring:

Guarder. Their SP rating is typically about “20” above where the “M” rating is at (varies between spring makers.

PDI. Difficult to acquire for some, but these are my favorite. Their % rating is based on % of a stock TM spring. 170% is an M115 ish. 190% is M120-125ish.

Arcturus stock.

Krytac stock.

All of these springs are capable of achieving ~1 FPS, which is where you should be aiming.

Do not buy:

SHS/rocket. Their silver springs are super soft, meaning they change over time, and will literally bend out of shape. Actually, their Japanese black springs aren’t horrific, but the inconsistencies in power keep me away from buying them when I have the chance. I will still use the black versions I have though.

For the final portion of this very long post, let’s discuss designing your build, and how to choose parts that complement each other.

First, you need to know what you want. What accuracy do you want? What BBs are you using? What FPS are you shooting? What does your field look like? These all affect what parts you choose: there is no flat “best”.

For my most recent build, I wanted a skirmish/CQB type rifle that was maneuverable and was accurate to 60 meters. I ended up keeping everything stock except for the hop rubber, which was replaced with a PDI W-hold 50 degree, and this nets me great accuracy with .25g, which is about the right ammo for the stock 60% cylinder and 265mm barrel. This one shoots just under 1.5J

For a buddy’s budget build, I kept the compression stock (it was all fine), kept the 363mm coated aluminum barrel (not ideal, but keeping it budget here), and the stock hop unit (just fine). The only thing I did was my little flathop mod, stabilize everything, and replace the nozzle with a modified plastic rando nozzle. It shoots great now. The barrel is the next upgrade to increase effective range, but the entire upgrade literally cost pennies, and transformed an average gun into an above average camping tool at 1.5J. I don’t remember what the effective range was at, but I was easily hitting a half-meter target past 60 meters (this was on a downhill slope, so max range was definitely increased… remember these are my subjective results—not writing a scientific journal here!)

On another build, designed for long distance, I used a T.N.T. S+ 387mm inner, along with a ML 60 degree MR.Hop, and a custom hard nub. This build can either be used with a full cylinder for .32g, or a 3/4 cylinder for .25g. The system is designed to work with up to an M140 spring, but can be run on all settings down to an M120 (lower will get you PME on FA). It’s also exhaustively stabilized—everything from cylinder head seating to stabilization on the very end up the inner barrel, inside the mock suppressor. This build takes me out past 70 meters with heavier ammo. It shoots just under 1.6J with .20g, but joule creeps higher when using heavier ammo.

Gas Bicycle part Auto part Audio equipment Automotive tire

This is a T.N.T. S+ barrel that’s been stabilized at the muzzle so it’s completely solid.

Finally, I have an even more accurate DMR in the works. This one will be based off an A&K SR-25, and will be designed to use .30g, though I’ll be able to simply change the barrel length to allow for heavier ammunition if I feel like it. The current parts list are: full SR-25 cylinder, 35g piston assembly, silicone buffer mod on a plastic CH, Lambda 6.08mm 509mm inner, ML 85 degree silicone MR.Hop, G&G rotary, and then I plan to use either an M130 to keep it under 450 FPS, or simply use an M150 and bump up to 500 (my field has a 50 foot MED for under 450, and a 100 foot MED for under 500). I’m hoping to create a build accurate out past 80 meters, though it’ll be a project for sure.

Each successive build has more and more changed parts, becoming more and more specialized into an accurized role. For example, the first build does not perform well on .30g, despite working great with .25g. Five hundredths of a gram. Amazing how big that tiny difference makes.

One final mod. The silicone buffer mod. This is very simple, but is more FPS consistent than sorbo and is also cheaper. You can find the guide stickied here.

Finger Thumb Nail Reptile Bivalve

In summary: parts fitment is key! This installment is about upgrading parts, but it’s also about fine-tuning and fitting your parts to each other for best accuracy!

The more times you do these mods and replacements, the better you’ll get at them, so keep on working!

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Discussion Starter · #3 · (Edited)
Airsoft Accuracy Advanced

I reference a few comments from users on Airsoftsociety, so I’ll be linking that thread here so y’all have easy access to the comments in question: HERE

All right. Aside from the video guides, demonstrations, and tuning videos I plan to put together, this is the final installment!

Ranges: 75-100 meters. You’ll notice this is a large spread compared to previous entries. This is because after 75-80 meters, accuracy becomes extremely “subjective”. By which I mean the tiniest of items become huge, and sometimes replicas simply won’t achieve accuracy of this level, despite everything seeming to be perfect. For example, in the comments of the Airsoft Society. version of this thread, @SiliconeSword discusses an issue where his outer barrel, despite seeming fine, was actually causing a huge deficit in accuracy.

In some ways, this will be the most complicated entry, but in other ways it’s by far the simplest. This is because most of the advice contained here can be summarized in one sentence: take everything from the previous posts, and then perfect it. Make it all tighter, more precise, straighter, smoother, and more level.

We will discuss: RHop, lapping, extreme build design, and durability,

Let’s begin.

Assess your replica again.

If you can’t reach, try heavier ammunition. .30g-.32g should get you to 75 meters with good conditions… but conditions are not always ideal, and you may want to shoot even farther. At these ranges you’ll want to at least consider trying out .36g, or even past .40g. To make accurate shots in the 80-90 meter range, some shooters prefer ammunition up to .48g, and some will even shell out the money for .69g ceramics, which are infinitely better than even the best BBs in terms of consistency and quality.

By now you should be good at tuning your rifle, and you should know how everything works together—this is the point where you have to start using your own tech intuition to figure out where to go next and how to fix issues. If your rifle is getting good groupings, but the shots are still falling short of your target, this is when you should consider increasing power. For 75-85 meters I typically prefer to shoot at 1.8-2.2 joules. Your experiences may differ, and since air resistance is exponential, increasing your power is an exercise in diminishing returns: worthwhile, but don’t expect to up your power to 3J and immediately be shooting 100 meters with pinpoint accuracy.

At this point, you’re a true DMR or sniper. If you’re using an AEG, you should probably be optimized for semi-auto only. This is for two reasons: first, you should be hitting precision shots, and full auto will hinder your development as a player. And second, full auto will greatly increase the stress on your system by nature of more rounds fired, as well as potentially hinder your accuracy.

When optimized for semi-auto, you can have a heavy piston assembly that would result in issues using full auto, allowing you to get more energy behind your BB when tuned properly. You can also implement items like air brakes, which cause issues in full. Very long barrels are also an option, particularly for replicas with large cylinder volumes like the SR-25 (the ones with the extended cylinder. Don’t get the other ones).

Durability. I won’t go into full detail, since this thread is primarily for accuracy. I’m mainly pointing out that when increasing power you need to take into account the durability of the whole system. A spring that’s only a little stronger than stock can sometimes wreck your gearbox drive train, and some replicas need durability mods OOTB. Do research on your particular replica, but the general rule is that you can run up to a full-stroke M130 on an ordinary V2 GB shell. This is the plain standard. Some shells crack on weaker springs, and some can take more punishment, but you should never expect the shell to take more than an M130 unless research points otherwise. Other gearbox versions are more inherently durable, but the V2 is the most common AEG gearbox on the market, so it’s the standard I’ll use. Some stock shells, like the Krytac Nautilus are extremely tough out of the box and can handle heavy springs, but most cannot.

Extreme build design. Aside from how you design your build, which we’ve already talked about, I define extreme design as any attribute that places your replica in an exclusive class, meaning you lack the abilities other replicas have in exchange for, in this case, greater accuracy. This is not necessarily a discussion about accuracy itself, but more about creating the gun around the play style you like, and not your play style around the gun. MEDs fall into this category. For my field, 400 FPS or under w/ .20g BBs marks you as a rifleman, with an MED of 20 feet. Above 400 is 50 feet, and above 450 is 100 feet. Despite maybe getting more range and accuracy, I keep my replicas under 400 except for specific builds where I take the trade. This limits me to maybe 70 meters of effective range during great conditions, but I take the trade since my MED is less than half of what the “DMR” role has, and one fifth of the “sniper” role. (at my field you can play any replica at any FPS, I’m just naming the categories) All of this to say, increasing your FPS does not get you more kills by itself and may put you into a disadvantageous category. Sometimes it’s worth it to increase your joule output, but FPS is not an upgrade, and you should consider carefully before doing so. Some fields also put shot limits on high FPS replicas, where you have to wait a certain period of time before enacting follow up shots on a target, and other limitations: research where you’ll be playing (backyard plinking doesn’t count).

RHop. RHop is fundamentally… genius. When properly installed, tuned, and used, RHop/IRHop is almost undisputedly the most accurate airsoft hop system. It provides extremely even and consistent hop, and can hop ultra heavy BBs with ease. (I won’t be writing out an RHop guide: you can find that on your own )

But now, the Leo breakdown: Hot take—RHop is not suitable for almost all airsoft players, and especially newer players. This is because of a series of requirements RHop imposes on you in order to get good performance, that other hop systems simply don’t.

Here are my reasons:

Even when bought in a kit, RHop is very finicky. You have to get it all correctly put together, and I find very few have the patience and skill to get it right. This results in issues, resulting in new players either thinking it’s normal, or becoming frustrated, resulting in a general degradation of airsoft society. Not to say that new players can’t put together the kit correctly and make it work, but that it’s finicky, and requires teching to work at full capacity.

For an example, as a starting player I bought an Elvishtac RHop kit, it came with a couple of little patches cut to fit perfectly with their barrel, and then a modify flat hop packing and flat nub. I put the thing together in a Prowin hop chamber… and it worked horribly. I remember shooting at a tree off a balcony and thinking it look like I was spraying a full auto shotgun.

My failure was not because of any of the parts, or the RHop itself, even though some of them could’ve been better. My failure was because I didn’t know the requirements.

No. 1 #: Must be able to deal with finicky nubs, centering, gluing, flat hop rubbers, and hop chambers (modify Fhop rubber has some issues, as do many of the common Fhop rubbers). Being a beginner I likely didn’t do everything perfectly.

No. 2 #: Must be using heavy, high quality BBs in order to have any accuracy gain over an ordinary type modern rubber. In fact, using BBs lighter than .30-.32g is actually detrimental to your accuracy over even a decent, basic stock rubber like the Krytac Orange. RHop is the most effective when used with .40g+.

No. 3 #: You have to already have a consistent air supply, inner barrel, etc, etc. RHop is an upgrade that enhances precision and range in the area of 5-10% over a good modern rubber, sometimes more and sometimes less. Unless your rifle is already a precise machine, RHop is no better than the other options.

In short, I do not use RHop in any of my current setups (this is subject to change), and I would recommend it only for tuners who already have a good grasp of how to make their rifles accurate, and intend on using only heavy BBs.

All that being said, RHop is still very, very good. For some extra tips and info beyond the usual RHop guides contain, visit @Ben3721 ‘s post in the comments on the Airsoftsociety version. (It’s the first reply post you can’t miss it.)

Lapping. This is a mod that is considered to be relatively high level, but that I absolutely recommend. The principle behind this mod is that, unlike simply polishing, you actually remove and high surfaces and even out the bore of your barrel, using diamond polish for steel and metal polish for brass, applied to “lapps”, which in this case are 6mm rods of brass, wood, or bamboo. The advantages are obvious; smoother barrel, smoother airflow, better accuracy! Some tests have suggested that it’s up to a 25% decrease in grouping size with certain barrels.

Since I’m not an experienced lapper myself, I tapped @SiliconeSword ‘s knowledge on the subject:

Here’s the link to his simplified lapping guide, which contains links to some of the materials you need to get started, as well as foundational knowledge about the mod itself: Superior Barrel Lapping Method

Beyond the simple guide, I’ll be adding more advanced details and tips as I learn them, both from SS and from my own experience, as I’ve decided to start lapping my own barrels using 6mm brass rods and diamond polishes.

That about wraps it up for the Advanced section! If you’ve worked through everything in this and the previous entries, you should be well on your way to putting together and creating accurised setups that give you a distinct advantage over the other players on the field.

It’s been a bit of a journey putting this together (I think I’ve cracked the 30 hour mark of writing and editing), but I’m not quite done yet. Here you’ll find my to-do list of things that are yet to be created and yet to be added;

Replica assessment video guide

Pseudo-flathop video guide

Hop tuning and setup video guide

DMR gearbox construction video guide

.25g BB testing (I’ll be making the winner my official recommendation for 60 meters and below)

Editing and formatting my posts! I’m writing and posting primarily on mobile, and my formatting resources are extremely limited, so when I acquire the time I’ll be formatting everything better on the desktop version of this forum.

That’s about it. As always comment, questions, and add!

Leo out.

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Excellent stuff, nothing to add or ask!

G&G Rotary. I really like this unit. They fit solidly on every barrel I’ve tried and provide consistent pressure. You can also get them cheaply if you keep an eye out. After having amazing success with my test buy, I purchased two from Umbrella Armory for $9 each.
You are a lucky monkey. I actually have a mod in mind for might be gilding the lily but if, like me, you tend to stick to one BB weight my idea was to add a small nutsert/rivet nut through the rotary dial in order to provide extra resistance to fight the propensity for some hop wheels to unwind under vibration. Probably an M2 or M2.5 and then a 3 or 4mm M2/M2.5 grub screw and a tiny dab of thread lock.


DaVinci and Edgi barrels. Expensive but of supreme quality. My Edgi is hands-down the best barrel I've ever used including PDI, Laylax, Prometheus, ML etc etc.

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Discussion Starter · #6 ·
Excellent stuff, nothing to add or ask!

You are a lucky monkey. I actually have a mod in mind for might be gilding the lily but if, like me, you tend to stick to one BB weight my idea was to add a small nutsert/rivet nut through the rotary dial in order to provide extra resistance to fight the propensity for some hop wheels to unwind under vibration.

DaVinci and Edgi barrels. Expensive but of supreme quality. My Edgi is hands-down the best barrel I've ever used including PDI, Laylax, Prometheus, ML etc etc.
Usually whenever I shim the hop arm it makes it too tight to come loose, but that sounds like a great mod nonetheless—you can also provide a similar effect with Teflon tape on the dial o-ring, but your version sounds great for locking hop in.

I’ll be discussing DaVinci and Edgi in later installments. Lambda squeaked in here because of the SMART series—$30ish really isn’t that bad considering how much a lot of the others cost.

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I think there are many routes to the same goal so as long as the mod is effective, all is well. This is actually an extremely relevant thread for me as I'm drifting away from the Silverback as it is simply too expensive to countenance right now.....a good old M4 could perform equally well without all the bells and whistles.

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Ah, Prometheus (and the related Nineball), they were once a good brand that offers good quality for the buck (like a budgeted PDI), but since some time ago their quality has gone down the gutter so significantly I've bought things from them (MWS hop up arm, inner barrels, some accessories) and only the mag release so far doesn't give me a headache somewhere

The accuracy they currently offer with their inner barrels are just so awful even literally stock Chinese AEG barrels have better grouping than them, I would not recommend them at all from whatever perspective, otherwise this guide is excellent and I've got nothing to add
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Discussion Starter · #9 ·
I’ve had a pretty good experience with the one Prometheus barrel that I own, hence why I didn’t mark them as complete trash, but they are in my “do not buy” category for good reason! I may be able to word that a little more strongly though: my intent was to point out that you should never buy Prometheus over other options, given that Lambda, Krytac, etc are both better and cheaper.

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627 Posts
Ah, Prometheus (and the related Nineball), they were once a good brand that offers good quality for the buck (like a budgeted PDI), but since some time ago their quality has gone down the gutter so significantly I've bought things from them (MWS hop up arm, inner barrels, some accessories) and only the mag release so far doesn't give me a headache somewhere

The accuracy they currently offer with their inner barrels are just so awful even literally stock Chinese AEG barrels have better grouping than them, I would not recommend them at all from whatever perspective, otherwise this guide is excellent and I've got nothing to add

Indeed, once upon a time, they didn't suck, we could find Tanio Koba barrels aplenty and Tanaka VSR conversion chambers were still manufactured!

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how much do you shim the movement to the sides of the hopupunit inside the outerbarrel?
do you shim until the O-rings push the hopupunit out of the barrel to the rear, without you touching it or do you shim it until you can push the hopupunit in and out, but it has zero room to move by itself?

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I think that a playing card wrapped around the chamber would be just about right, I'll try this in a little bit and get back to you about it. If there is space, it should probably be filled though.

The O-ring thing is to replace the standard spring that comes with most guns and hop units. You want to add O-rings over your inner barrel until you feel a bit of pressure when reassembling your gun, which will be from pressing your hop chamber into your gearbox.

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Discussion Starter · #15 ·
Usually when I do my cork mod it solves both issues at once, since the cork compresses into the shape that the hop chamber puts upon it. If it doesn’t, or I’m using barrel O-rings, I’ll just do a single piece of aluminum tape wrapped around the hop unit to cover both “stabilization wings”.

I’ll echo SS—you want it to be tight enough that everything fits solidly. I usually do a finger test to see if I can wiggle the feed tube by hand. If I can, it’s not ready yet.

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Usually when I do my cork mod it solves both issues at once, since the cork compresses into the shape that the hop chamber puts upon it. If it doesn’t, or I’m using barrel O-rings, I’ll just do a single piece of aluminum tape wrapped around the hop unit to cover both “stabilization wings”.

I’ll echo SS—you want it to be tight enough that everything fits solidly. I usually do a finger test to see if I can wiggle the feed tube by hand. If I can, it’s not ready yet.
what cork parts do you use for the shims? I assume I dont need to get lots of wine bottles?

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Discussion Starter · #17 ·
I literally just used a wine cork I had lying around. Since the buffer is small, and only needs to be about 1/4” thick, you can make at least a dozen from a single cork.

I suspect neoprene or sorbothane would also work here, as well as any other material that allows for slight compression under stress.
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