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Discussion Starter · #1 ·
Hey! I'm sorta new here. Been more of a lurker really.

I would like to maybe hear some opinions/Criticism about a build im currently working on!

Goal: A 450 FPS rifle, as quiet, accurate, consistent and as good trigger response as possible!

Base gun: A VFC SR15 (Yeah I Know, a 5.56 :S)


Internals
:
-SHS 13:1 gears
-Super shooter(SHS) M170 spring SS'd 3 teeth
-SHS Piston
-Lonex POM Piston head
-VFC Cylinder (Gives a good airseal)
-ZCI Cylinder head
-G&G Nozzle
-SHS Tappet plate
-VFC stock ARL
-Prommy straight trigger

Electrical:
-ZCI High Torque 22TPA motor
-11.1V 40-60C battery
- BTC Spectre

Inner barrel etc:
-ZCI 6,02 407mm inner barrel, R hopped
-Stock VFC Hop unit
-Prommy Flat nub
 

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Is this a recent purchase?

It sounds a lot like an AEG someone I know bought used and ended up sending back due to all sorts of issues . . . from crushed/exposed wires to a short stroke job that looked like it was performed by a beaver.

Also, intro posts are lovely things.
 

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- Work within your skill level.
Whatever that is, it would be better to have a great performing gun at the level you are capable of building one vs a poor performing gun that on paper has the latest ad greatest parts and modifications.

- Goal: 450 fps:
You do not need an m170 spring to achieve this and I would highly advise against this power level of spring.
An m130 spring should give you all of the fps you are looking for.

- Air Volume:
You want as much air volume out of the Gearbox that you can get.
It would be advisable to go with a full stroke set-up vs one that is short stroked.
You also need a Full Cylinder.

- Inner barrel:
Quality Inner Barrel of 455mm in length.
Bore size is up to you. I prefer 6.03tbb's at the moment, but have never tested wbb's for comparison, which have a growing reputation among experienced airsoft techs.

- Semi-Only Selector Plate Mod.
Know the difference between an upgraded assault rifle and a DMR.
Don'y rely on the features and options of a Power Control Unit to electronically control this.
Fully commit to a DMR build or do not build one.

- Quality Bucking:
Whether you are simply using a Drop-in Bucking or implementing Hop-up modifications such as Flat-hop and R-hop variants, get a good Bucking.
This will assist in improving air seal as well as bb performance.
Suggestions:
1. Lonex 70 Degree
2. G&G Green
3. Lonex 50 Degree

- Quality Heavy Ammo:
No way around this.
If you are not willing to spend the money to get the best quality heavy ammo you can afford, and to purchase some measure of quantity of it, do not waste your time building a DMR.

Advice:
The above is a baseline to follow and get you going in the right direction.
As for parts, modifications, and brands, that is for you to do your research and for others to answer those questions for you.
With the advances in airsoft technology and a now better understanding of the science that goes into increasing the performance of an airsoft gun, it would be easy to get weighted down by all of this in your decision processes.
So, keep it simple.
Don't be in a rush to get up to speed or to get ahead of the curve.
Do what you are capable of doing, and step by step grow in your knowledge and capability.
Slower is definitely faster when new or simply not experienced in DMR builds.
Have fun and keep us posted on your gun build.
 

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Discussion Starter · #4 ·
Skill Level: Im pretty comfortable with building a DMR. I know it takes A LOT of work, but Im willing to work for it. I build rifles for customers, I've buildt 2 DSGs that shoot 55 RPS and 62 RPS at 340 FPS and so on. The reason behind wanting to build this DMR is because I've buildt soooo many High speed builds, but I would like to build more DMRs!

Why the M170?
The reason why I wanted to go with a M170 spring is that I have 2 of them laying around here, So I did some math and figured that if I use one, short stroke 3 teeth off it it will land at around 440-450 FPS. and as a plus, it will also give me even better trigger response! :3
As for what I've done in order not to have it break the gearbox or anything, Ive radiused and fixed AOE!

Cylinder
The Cylinder is already full!


Barrel: I Know that the inner barrel is sorta the omega of DMRs, but ZCI barrels are actually pretty nice once you clean out the barrel once you get it, maybe even polish it alittle!

Why a Spectre?
Well, The reason why I actually want a spectre in there is actually because I Love them, I have 3 laying around and it will help on trigger response, I can program it for Precocking if I want to and Semi only! I know its not nessesary though. I know 3 ways already on how to make it Semi only!

Bucking
Since its R-hopped, I dont really need a superfancy awesome bucking. I am using a purple prommy though cause I have a bunch of them and their quality is nice and consistent!

Ammo:
Im waiting for a order with BBs from BB Bastard, but right now im using madbull!



@Corriander

And no, This isnt anything Ive bought used xD It was a rifle I had that I decided to build into a DMR
 

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Yeah Vanevery, what do you have against using a spectre for semi auto lockout? It is easily reversible for troubleshooting or whatever else you would need. I run mine with semi auto selector position as pre-cocking, and full auto as semi without pre-cocking. Works very well for a DMR.

Springs are cheap. It is not worth the work of modifying the sector gear just to save on a spring. Also, it will hurt your trigger response, even short stroked, because the load on the system is still pulling a M170. Think about trying to compress a M170 cut down a few coils vs compressing a M130. The shorter spring HAS to be stiffer.

It will also be trickier to get the pre-cocking set on a short stroked system.
 

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But if you shortstroke you will not use all the potential air from the cylinder, he meant that you should not shortstroke so you can use all the air from the full cylinder.
And why you should use a quality bucking is because of airseal with rhop. Maybe consider er hop? Or ier hop if you live in a cold country.


Sent from my iPad using Tapatalk HD
 

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Discussion Starter · #7 ·
@Skywalker
Yeah I See your point. The precocking can indeed be a bit tricky with shortstroking, Didnt think of that.. Thanks!

@baracken
I already have a R-hopped barrel here, and Prometheus is one of the companies that makes the highest and most consistent quality there is, so the bucking part is secured.
 

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Vanevery's post is a copy-and-pasted text that he posts for every person asking about DMR building advice. He either didn't read your post in its entirety or did, and decided to not make any modifications to his pre-written response anyway.

As has been mentioned before, don't short stroke with a DMR. You want the maximum amount of air volume possible with an AEG DMR.

Whether or not you use the Spectre, you still need to permanently modify the selector plate for semi-auto use only. 99% of legal fields require that a DMR be permanently modified for semi-auto use only. The Spectre does not fulfill that requirement. Use the Spectre for precocking, but still modify the selector plate (with the Spectre, is that even possible since it uses switches rather than the cutoff lever?).

Prometheus is an excellent company. However, HS5 has specifically recommended the Lonex as working best with R/ER hops.

And get a better barrel than the ZCI unless you lap it like crazy. Even then, Prometheus could still use lapping. The only barrels that don't need them are PDI/EdGI, and even then, I lap mine.

DIY modifications are a given. Air seal modifications must be done throughout. Barrel stabilization must also be considered. If necessary, shimming the hop-up would also be wise.

DSGs =/= DMRs. The modifications and mindset needed to create both are different. Take heed of vanevery's post and check out the other guides on this forum regarding DMR building.
 

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I have never had that experience. As long as my DMR does not shoot full auto in either fire selector position, it is deemed field legal.

For the record, the selector plate mod should still work with a Spectre.
 

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Starting with internals, I've never been a fan of Franken-boxes . . . particularly on a DMR. I understand the periodic necessity due to either budget or utilizing what happens to be lying around but the minor tolerance variations between brands have a tendency of showing up on the chrono. Pick a quality brand and stick with it.

Short stroking and DMR are not two things that go together. Removing 3 teeth equates to 20% less piston pull putting the release point closer to what would be used to volume a barrel length under 400mm. A DMR should be utilizing a barrel length of 455mm or greater (dependent on air pressure source) so use an uncut sector gear and lower rate spring.

Consider doing a cost analysis between the parts and labor involved assembling a mechanical gearbox and putting in a HPA alternative.
 

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Discussion Starter · #12 ·
I dont really belive in picking 1 brand and buying all its parts to be honest xD If gears mesh well, they mesh well. If The compression parts give a good airseal, they give a good airseal. And yeah, Everyone else also mentioned Shortstroking.

I also dont really belive that a DMR "need to have" a barrel that is 450mm+. I think a DMR can do well with just a 400mm barrel aswell
 

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Yeah Vanevery, what do you have against using a spectre for semi auto lockout? It is easily reversible for troubleshooting or whatever else you would need. I run mine with semi auto selector position as pre-cocking, and full auto as semi without pre-cocking. Works very well for a DMR.

Springs are cheap. It is not worth the work of modifying the sector gear just to save on a spring. Also, it will hurt your trigger response, even short stroked, because the load on the system is still pulling a M170. Think about trying to compress a M170 cut down a few coils vs compressing a M130. The shorter spring HAS to be stiffer.
It will also be trickier to get the pre-cocking set on a short stroked system.
Few points on that.
1. In my experience through the years with giving advice or helping someone step by step with their gun build, there seems to be a pattern with most who ask for DMR advice specifically, not knowing the difference between an upgraded assault rifle and a DMR.
The clear majority of those in this case who choose to go with ECU's to control the Fire Mode, and not make a permanent modification for semi-auto only, are in almost every case not willing to follow through with key points of advice offered for DMR builds.
Thus, their guns do not perform as they expected and they endlessly "circle the wagon" with return questions that have already been answered repeatedly in the step by step process leading up to the finished product.

So, it is just from experience that I advise those interested in DMR's specifically, to make the Fire-Mode adjustment a permanent one from inside the gun, and that cannot be changed from the push of a button.
Those who are willing to do this have proven to be much better listeners to the entirety of advice given, and have proven more likely to succeed with the finished product the first time around.
Like anything else in life, there are "tells" that often let you know how the following steps are going to go.
This is one that has repeated itself endlessly in my experience.

2. Non-permanent Fire-Mode changes, such as the ones with ECU's as in the Spectre Mosfet Unit, are often simply not allowed at many, if not most, airsoft fields. This for the simple fact that the gun's performance can be easily set to pass chrono regulations, and then easily altered to field a non-legal airsoft gun. Similar in concept to those who use air rigs, having to lock them down with zip ties.

3. Cost incentive.
A DMR simply needs a basic fet to do the job.
An expensive ECU with multiple functions and options is simply not necessary at all for the purposes of a DMR.
One could make the case that such an ECU can assist with trigger response, and I would agree.
For the cost vs reward aspect of that view point, I would disagree.
 

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Vanevery's post is a copy-and-pasted text that he posts for every person asking about DMR building advice. He either didn't read your post in its entirety or did, and decided to not make any modifications to his pre-written response anyway.
The thoughts and suggestions I have offered in this thread are in fact similar to many things I have said on this forum and others for a long time. In many parts, word for word.
I did actually type my posts out and currently have no copy/paste responses for DMR threads specifically, though that is actually not a bad idea.
I in fact did read the OP in its entirety and did in fact address some of the specific thoughts the OP had. My intentions are to help point the OP in the right direction.
There are only so many different ways to say the same thing.

When it comes to parts and even modifications, people can have all sorts of different opinions on what brand of this or that to get, what modification is a must and what is not.
Sometimes I offer my thoughts on that sometimes I don't. I have my favorites like everyone else.
Too often threads can get derailed from endless back and forth arguments on parts and brands of parts, and modifications.
So, I have learned to stay out of that when I can.

Specifically regarding DMR's, one can have whatever opinions they want about parts and modifications, but there is a baseline that qualifies a DMR to be a DMR regardless.
That would be:
1. Full Cylinder of some kind.
Max air volume requires non-ported cylinders.
2. A properly balanced air volumed barrel to match the Cylinder, which is typically around 455mm's in length for your off the shelf Full Cylinder.
3. A permanent modification to the Fire-Mode set in semi-auto.
4. Quality heavy ammo.

You can have a fully tuned gun, and not have a DMR.
You can have an ECU with every available option that science fiction will allow, and not have a DMR.
You can have the latest and greatest brands of parts, and not have a DMR.
You can implement every modification known, and not have a DMR.
You can have a different barrel, with a different brand Hop-up Unit, and a different Hop-up mod in each respective barrel until you run out of Hop-up mods to implement, and not have a DMR.
You can have all you want, but if you do not have the 4 baseline qualifications mentioned above, you do not have a DMR.

Much, if not most, of my knowledge regarding DMR's comes from first hand experience in real world testing with a firing lane set up, and distances measured off. Literally hundreds of hours in the last two years at the Range alone, not including the actual time spent working on the airsoft guns themselves.
My approach to testing is:
1. Education of existing knowledge.
2. Work within the box, test to verify conventional wisdom, define the box.
3. Work outside the box, test any and all ideas of my own originality, test any good ideas that are openly discussed and originated by others, but not-verified.

Some things I have learned:
- 90% of advice given on tech related subjects is based on what someone else said, not direct first hand knowledge of the subject. In many cases, the average tech really has no true idea, they just heard it from someone else.
- Most of the information out there regarding building and performance of DMR's specifically is simply incorrect, false, or just simply bad information.
- Most advice given to novice airsoft techs is misguided and not helpful to achieving an actual result.
- For all the advancement in airsoft knowledge, understanding, and technology and for all the widespread of information out there in the forum universe, a novice airsoft tech today struggles more than they did ten years ago to simply complete a basic airsoft gun build.
Why? because every novice airsoft tech tries to go from zero to hero in record time to get up to speed with current possible airsoft gun performance.
While this may be human nature, it is also the influence and direction that is given by the majority of experienced airsoft techs.
The result: Novice airsoft techs take longer than ever to complete a simple gun build, skip steps in the learning process, and often burn out and quit as a result.

Less is more.
Anyone can take the above 4 step process and build a DMR that can outshoot the majority of DMR's on the majority of airsoft fields.
Why? Because the majority of DMR's out there:
1. Do not have enough air volume.
2. Do not have the correct size barrel nor the correct cylinder.
3. Have an ECU that was poorly installed so thus will burst fire or even full-auto fire due to electrical shorting in the wiring.
4. Refuse to spend the money for quality heavy ammo.

So, the advice I give is based on what I directly know.
What I know is that for years most have been able to out shoot other DMR's that have the latest and greatest of every brand of part and modification simply utilizing the knowledge of the 4 simple steps above.
Even more so as their skills, knowledge, and capabilities grow and when they get up to speed with todays science.

This is why I always say: Build towards your performance goals, do not chase them.
 

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I had to comment on this thread. It made me laugh a little.

I made a DMR that shot accurately to 70-80m with 420fps. The inner barrel was only about 130mm long. LOL. I used 0.3gm bb's in it.
To me a DMR is a Semi Auto rifle that can fire further and more accurately than a full auto up close weapon (auto weapon). So in effect you could make an AK beta into a DMR as long as it can outdo the assault rifles.

Also, it can be good to use an extra large spring and cut it down to the desired FPS you want. If you do this, the spring is not under much tension when the piston is not engaged. For example, if you use an M190 spring and cut off about 5 coils you will end up with a spring that fires about 450fps (give or take some) and it will only be under a really small amount of compression when fitted between the spring guide and the piston.
 

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The thoughts and suggestions I have offered in this thread are in fact similar to many things I have said on this forum and others for a long time. In many parts, word for word.
I did actually type my posts out and currently have no copy/paste responses for DMR threads specifically, though that is actually not a bad idea.
I in fact did read the OP in its entirety and did in fact address some of the specific thoughts the OP had. My intentions are to help point the OP in the right direction.
There are only so many different ways to say the same thing.
I must apologize then for my incorrect assumption. I've seen and read your responses to "I want to build a DMR" topics so many times, that after the fifth or sixth time, I simply assumed you copy and pasted everything since they all sounded almost identical.
 

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I must apologize then for my incorrect assumption. I've seen and read your responses to "I want to build a DMR" topics so many times, that after the fifth or sixth time, I simply assumed you copy and pasted everything since they all sounded almost identical.
No need to apologize.
A lot of my replies to these types of threads are similar in nature and I have tended to repeat myself word for word a lot lately.
My long response to your post was not intended to debate or get into any type of tit for tat on DMR philosophy and approach.
I was really just trying to make myself clear on where I was coming from.

You have grown a lot in your own knowledge and skill as a tech.
I remeber you from years past on the KWA forums and have seen you on other forums such as this one.
I would bet you have a growing number of requests in PM's for advice and guidance for various tech questions and gun builds.
The point is, in a couple years, and after a few hundred Q&A's in PM's and threads such as this one, you are going to get to a point of realizing that most people just don't listen.
This has nothing to do with the OP in this thread, for it is clear to me the OP is a competent tech and has experience.
Just generally speaking on the point that most who ask for advice really have no intention on following the full extent of it.

What I am getting at specific to DMR's, is that most DMR threads get hung up and even derailed on debates over parts brands and modifications and whatever else.
Most of which has nothing to do with base function, set up, or qualification of what a DMR really is and the starting point for how to get there.
So, the one asking advice usually ends up with a "gun build" that has about the most piss poor performance they can manage to squeeze out of it.
Piss poor R-hop install.
Piss poor functioning mosfet install.
Piss poor screeching Bevel/Pinion shim job.
AOE correction with the added sorbo falling apart day one.
Etc.....
All in an attempt to have a super performing gun that ends up a super failure and with an empty wallet.
All of which can be out shot by about any gun on the field.

I also mean it when I tell you that you can take about any AEG and:
1. Drop in a Full Cylinder
2. Drop in a 455mm Inner Barrel
3. implement a Semi-Auto Only Selector Plate Mod
4. Get some quality .32 bb's
5. Throw in a standard m120 spring netting around 390-400 fps for some added pop
..............and literally out shoot over 50% of claimed DMR's on about any airsoft field in America.
I have seen this for years and it never fails.

I am all about obtaining the latest knowledge, pushing the envelope in performance, and building the greatest airsoft gun you can.
I have in fact spent the last two years trying to do just that in my own gun projects.
I will tell you, though, that I am a crawl, walk, run kind of guy.
I am all about foundation building.
This approach usually proves faster, smoother, and less expensive in the long run.
After years of seeing what could be the next generation of very good airsoft techs fail and quit for they skip steps, get frustrated, and go broke trying to get there, I go out of my way to influence the simple approach as a starting point for tech related questions.
I will guarantee you the airsoft community has lost many more good airsoft techs due to quitting in the past five years than the previous five years leading up to that time frame.
 

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Discussion Starter · #18 ·
Gotta agree with 1tonne here.
I dont think that a DMR is defined by how long the inner barrel is, but that its able to outrange other rifles and that its very accurate and consistent.

I also have nothing against making my DMR 'permanently semi only', although I could just change the selector plate and have it back on full auto If I wish. I Sorta just LOVE the BTC spectres and Im at the point where all rifles without one feels incomplete. (Goes more for my main rifles)
But in the end, Im not someone who will just simply give up cause I failed at the first try, if not I would have stopped teching 7 years ago xD
I will spend hours and hours on this rifle, tuning it until I feel its perfect.

And thanks for all your insights and tips, vanevery.
On another note though, Have you ever used a SHS/Super shooter spring? I Know that the FPS vary from brand to brand, like a Prometheus M140 might give 500 FPS while maybe a SHS will give 450 etc >.>
Have you ever used a M140 or something from SHS? How is the FPS on one? (I have a bunch of SHS springs here..)
 

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On another note though, Have you ever used a SHS/Super shooter spring?
I have a SHS M140 in my shop that ended up being overpowered for the application, putting out ~475fps on testing. Switching to an Prometheus M135 brought the output to ~435fps. While not a direct test of M140 vs M140, the SHS seems to be slightly stiffer than a Prometheus.

I usually tend to install half a step down then preload with a machined collar on the spring guide.

The 455mm inner barrel length debate for DMR's is mostly centered on matching the output volume of a full cylinder in an AEG. Can shorter be accurate? Sure. So can longer. On my range, in side by side tests, I have had better accuracy past the 250ft mark in barrels between 455mm and 500mm than those shorter or longer. I've achieved greater range with longer barrels, but that's on a HPA system not limited by cylinder volume.

In practice, I have seen 400mm is the point where a system starts showing it's distance potential. 450mm is where that distance and accuracy begin to align. Past 500mm (unless LRB'ed) is where distance and accuracy begin to diverge again.

An example of this are two P* M4's I ranged side by side. They were internally identical except one had a 400mm Orga and the other a 500mm Orga (with poppet dwell adjusted accordingly). Both shoot 300-310ft but the 500mm Orga maintains an accuracy advantage over the last 50ft of the flight path.

Length is only part of the equation though. Inner bore quality matters just as much and is not something achieved with an off-the-shelf product. A properly lapped/polished stock brass barrel will outperform almost every barrel on the market. Get yourself a selection of diamond paste ranging from around 20microns down to 0.5microns and set aside a couple hours to get it done right. If you source the pastes from Hong Kong instead of from the domestic US you can get them for about half as much.
 
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