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16 Posts
Discussion Starter · #1 ·
Hi this is my first post but I have been trying to really increase the accuracy and range of my ICS sportline m16. I recently bought the upgraded m120(i think) upper part of the gearbox. But now I need accuracy and range. After doing alot of research on different spacers like scs(same as rhop right) then h nubs and flat nubs. Then different buckings with all sorts of different insides(like angle customs v teeth). It has all kind of overwhelmed and confused me:nuts: Can someone give me a clear answer on what combination of spacer and bucking works the best for them? What barrel would work best as well?? If anyone has experience with an ICS m16, it would help. It has a stock 509mm(510?) barrel. I currently own an SCS nub and I am using it on a standard bucking but it is defiantly not offering the best accuracy. Thanks in advance!:cheers:

554 Posts
Flat-hop and R-hop are Hop up mods.
Using a Flat-nub or an SCS Nub does not make your gun Flat-hopped or R-hopped.

Buckings are used for three purposes:
1. Hold the Hop-up unit secure to the inner barrel.
2. Provide Hop by the rubber of the Bucking contacting the BB.
3. Provide air seal via the Bucking Lips with the Air Nozzle.

Drop-in Buckings are standard Buckings that come stock with airsoft guns. There are also after-market drop-in Buckings that you can buy that are usually better quality than the stock Bucking.
Better quality Buckings can increase range and accuracy with your gun.
Most Buckings come in soft, medium, and hard degrees.
Soft for high speed and low fps set-ups.
Medium for mid-range guns
Hard for high power set-ups.

Bucking Mound and V-teeth:
A standard Bucking has what is known as a mound.
A mound is a hump in the inside of the bucking that the BB passes over when shot. This hump is located on the Bucking directly over the barrel window of the inner barrel. When the BB passes over the Bucking mound, it presses into it as if it is flattening the mound.

V teeth are another approach/design of a Bucking mound where the mound is actually semi-replaced by twin fins of rubber. I say semi replaced because in some V-teeth designs, the V-teeth actually stand on top of a shortened Bucking mound. The idea is that when the BB passes over the V-teeth, the V-teeth will cup the BB and give the BB greater stability.
FireFly V-shaped Buckings and KWA 2g Buckings are examples of this design.

Buckings need Nubs to apply pressure to the Bucking.
This is always true unless doing advanced modding that may not require the Nub.

- Standard Nubs are Oval shaped.
ICS Hop Up Spacer by: ICS - Airsoft GI - the largest airsoft store on

- Specialty Nubs like the SCS Nub or X-Nubs are designed to let the BB be cupped by the Bucking mound as the BB passes over it. This gives the BB more control and stability vs Oval shaped Nubs.
SCS Nub:
Shredder's Custom Works - Shredder's Concave Spacer (SCS)
Madbull X- Nub:
Madbull Red Hop Up Bucking by: Madbull Airsoft - Airsoft GI - the

- Flat Nubs have a flat top surface and a concave base to fit into the place holder on the Hop-up Chamber Arm.
FireFly Buffer Rubber is the industry standard for Flat-Nubs.
Firefly Buffer Rubber for AEG Hard - Airsoft Atlanta

General Function of the Hop-up Unit:
1. Turning the Wheel Gears on the Hop-up Unit raises and lowers the Hop-up Chamber Arm.
2. The Nub sits in a place holder on the Chamber Arm.
3. As the Chamber Arm is raised and lowered, the Nub will pass through a cut out in the inner barrel known as the barrel window.
4. The Nub will then meet the Bucking rubber at the base of the mound.
5. The Nub applies pressure to this mound thus raising and lowering it.
6. The more the Bucking mound is pushed into the inner barrel, the more Hop is applied, the farther you shoot. The less the Bucking mound is inside the inner barrel, the less Hop is applied, the less distance you shoot.

(Credit: Star_Folder)
1. Turn Bucking inside-out.
2. Shave off Bucking mound and Bucking Ridge that secures Bucking in place on the inner barrel.
3. Turn Bucking rightside-in.
4. Use Flat Nub instead of standard Nub.

Allows more surface contact between the bb and Bucking due to a flat piece of rubber raising and lowering in the inner barrel vs a mound. Think of a Bucking mound as a speed bump. Think of Flat hop as a runway.

(Credit: hunterseeker5)
This is a patch that fills the space in the barrel window of the inner barrel. So, applying pressure with a Nub pushes on the bucking which pushes on the patch. In this case, there is no Bucking material whatsoever touching the BB, only the patch.
Basic Install:
1. Turn Bucking inside-out.
2. Shave off Bucking mound. Bucking Ridge is optional.
3. Cut the length of the patch to fit barrel window. Measure twice/cut once.
4. Sand R-hop patch Outer side to be flush with the OD(Outer Diameter) of the inner barrel.
5. Radius the trailing edge of the R-hop patch. This does not take much.
6. Sand the inside of the patch.
This where the fine tuning begins.
There are several approaches to this part to tune the patch for given distances along with given weights of BB's.
Typically speaking, a basic R-hop install sands the patch to be flush with the inside of the inner barrel as the patch sits in the inner barrel window. This is a good starting point for your first attempts at R-hop. The more experience you gain at R-hop, the better you can sand the R-hop patch specific to distance and BB weight.

Allows for more contact surface with the BB and the material it is contacting.
In this case a patch, not the Bucking.
This also eliminates the distance the Bucking has to raise and lower as it raises and lowers in the barrel window such as in using standard Nubs and even Flat-hop, for the patch is already at the surface of the barrel window.
Think of the R-hop patch as a runway with a ramp.

16 Posts
Discussion Starter · #4 ·
Thank you Vanevery for the reply. It has defiantly helped me learn a lot about the difference between rhop mods and regular spacers or nubs. I did not know that rhop mods were anything of the sort. I just thought an rhop was a type of spacer before. Thank you for the long and thoughtful reply too. I am looking more into an rhop mod. I think I will research it some more before buying the patch though. Do you have a preference between Flat-hop and R-hop?

554 Posts
My suggestion would be to take a step back, assess your skill level, and make decisions based on what is best for building you foundation in tech knowledge. When it comes to working on airsoft guns, the worst thing you can do is skip steps. If you are new to working on airsoft guns, don't try to go from zero to hero over night. Build your foundation of knowledge and basic skill.

Specifically regarding the subject at hand:
Whether you are doing Bucking swaps or Hop-up mods such as Flat-hop and R-hop, you need to start by knowing how and being proficient at dis-assembly and then re-assembly of the Hop-up Unit.
This will allow for proper cleaning of Inner Barrels, Buckings, Nubs, the Hop-up Unit itself, seating the Nub correctly on the Chamber Arm, and for doing Hop-up modifications such as Flat-hop R-hop and more.

I always dis-assemble my Hop-up units for even basic Bucking changes.
This allows for proper seating of the Nub, which often gets pushed out of position when trying to insert the Inner Barrel with Bucking attached in a straight-up barrel install. It just always ends up being much faster to for me to do it this way. Taking the Hop-up unit apart is not hard to do nor understand how to do it. It will, however, take a walk through of a few times reading how to and actually doing it to become proficient at it.

Where to start:
You would be well served to be proficient at changing out your stock Bucking and trying different high quality drop-in Buckings. Truthfully speaking, quality drop-in buckings never really were fully tested to their limits of performance before Flat-hop and R-hop became of age. So, everyone now automatically assumes that Flat-hop and R-hop are always better for every shooting performance goal. This is not the case in my experience.

Flat-hop and R-hop are best for truly long range guns.
For when you want accuracy beginning at 300' (100 yards).
If you are shooting less than 300', then you can achieve fantastic accuracy with a quality drop-in bucking. This provided you have a quality Inner Barrel and are using quality ammo.
Having said all that, if you are using a gun that has an inner barrel of less than 300mm or have a CQB Type 3 or 4 Cylinder in your gearbox, then a Flat-hop or R-hop would provide better performance than a drop-in Bucking.

So, my suggestion would be to start at the beginning.
Install quality drop-in Buckings and experiment with different types of Nubs. Then become proficient at Flat-hop, then R-hop.

16 Posts
Discussion Starter · #6 · (Edited)
Once again thank you for the reply. I am glad you told me all this over just a quick reply saying what works for you. This weekend I will learn how to take the hopup apart and re-install it like you suggested. I haven't done it yet because I never thought I really needed too and all the small springs and little parts kept me from trying. I do have the angle custom V-teeth bucking but I use my stock bucking now because it will not go on the barrel right. The end where the nozzle hits always ends up too far forward and deforms/squishes in front of the barrel. I haven't heard the best about Angel custom so maybe that's why their bucking is hard to install. I will order maybe 2 new buckings soon and try them out. This will help me build up until I can start trying a Flat-hop. I was thinking the prommy purple and maybe a madbull red bucking with x-nub. Can you suggest any experience with a drop in bucking you like? Have you tried the V-teeth ones? I do not want to rely off the experience I had with my angel custom V-teeth as I'v just had bad luck with it. Which might or might not bee the V-teeth design's fault. I would try out a lot of different buckings, but I don't want to spend too much money on it. Thank you for your time.

554 Posts
My favorite all time Buckings:
1. Lonex 70 Degree
2. G&G Green
3. Prommy Purple.

Of the three, I suggest starting with the Prommy Purple.
The Lonex 70 Degree may be the best performer, but requires silicone oil to install due to its thickness.
The G&G Green works best with a minimum of .30 bb's.
A Prommy Purple is simply less fussy when learning how to install Buckings.

One more thing.
You may find that the Bucking stretches into the C-clip area of the Hop-up Unit when installed. If this is the case, it is ok to trim the bucking at the C-clip end in order to allow for the C-clip to lock onto the Hop-up Unit properly.
I will PM you a link to a walk through on how to dis-assemble the Hop-up Unit.

16 Posts
Discussion Starter · #8 ·
Alright I will order me one Prommy purple, and one Lonex 70 degree. I usually use .25 bb's so G&G wouldn't work for me for now. I will use heavier bb's once I improve my m16 some more. Right now I am just playing with some friends in my woods. Most of them have basic guns and are not that into airsoft so they always use my bbs lol. When I start going to actual airsoft places and improve my m16 to be more of a dmr, I will start trying out heavier bbs.
Trimming the bucking will probably help. I didn't think it would be good for it at 1st. And thank you for sending the pm.
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