Thanks to buppus for the nice intro he posted in another thread:


Well, now that has been all summed up, I figured enough 'background' testing has gone on and I'll go ahead and post up what I and other people have found out about the Flat Hop.

Initially, Age gave me the idea of removing the internal mound and making a flat nub. Initially I got good results, but wasn't really impressed, and quickly switch back to normal nubs. Then the G-Hop came out, and it got me thinking. So I revisited the advice I had received, and I guess knowing more than I did then, I found my problem. Removing the internal mound is messy business. That the internal sides of the bucking are much smoother than where the mound used to be. So I removed the internal rib that locks it into place, turned the bucking in such a way that the smooth inner wall had contact with the bb, and I used a Firefly Buffer Rubber as the nub. Instant 300ft torso shots in my DMR. And thus the Flat hop was born.

I started doing experiments, seeing how different nubs effected the system. I had reasonable success with small, flat pieces of metal, glued to the stock nub. But, you have to be very precise. Too big, and it will act like scissors with your barrel, cutting your bucking. Too small and it won't be as effective as it could be. The Firefly nub is still the best option.

Next came some help from Soccer77. I don't remember what he asked me, or why we started talking, just that we did. I told him about the bucking mod and he tried it on his KWA DMR. He was getting 7/10 hits on a tree 117yards away, I believe was his claim. I similarly tried both a Madbull and Systema bucking, and got better results with the systema bucking. Turns out, you get better results with thinner buckings. I believe this goes along with the "more contact with the bucking" idea. Using a thicker bucking like the Madbull and it isn't thin enough to conform around the nub, still creating a curved *mound* that the bb goes under.

Then I talked with buppus. Told him about the mod, he tried it out. First he didn't get such great results, he changed some stuff around, and got very good results. I noticed that they weren't quite as good as I was getting, so I asked him about his set up. Turns out he was using a PDI 6.01 barrel. Soccer77 and I are/were using EdGI 6.03 and Prometheus 603 barrels respectively. I did some research, talked with buppus a bit, started a thread asking about the hop up window of different barrel brands, and yee245 provide some, thank you yee. Turns out that the smaller hop up window of the PDI barrels doesn't help the hop up mod. Like we've said, for it to work, you need more contact with the bb. The smaller window of the PDI barrel limits this. But, buppus still saw better results, as he said above.

So yeah, that's where I am now. I think I talked with a few others somewhere through there. Sorry if I didn't mention your name. It seems like the best way to do this hop up mod is to have a Prometheus barrel, KWA 2GX bucking with the nub and inner ridge removed, and a Firefly Buffer Rubber.

Try it out if you can, tell us what happens, tell us what issues you have with it, or if you find something that helps it even more. It's a bit of an ongoing project. Currently I'm researching the possibilities of extending the hop up window of a barrel to increase the contact even more so.

Like I said earlier, I was able to get 300ft torso shots, 8/10, at 500fps. I was using Madbull .4g bbs, and the barrel was a Prometheus 6.03, 550mm. This was in my L85.

I've also installed this hop up in a few team mates guns, and several other people's guns. In a stock CM shooting 1J, I was able to get reliable 200ft torso shots, and it has full auto. Everything about the gun was stock, I did all the mods I would normally do to any DMR, so I guess it's a little special in that aspect, but, for the most part, it is a stock gun.

Again, if you can, try it out, Post up your results. Let's see how far we can push the system.

----------------------------------------------------------------------------------------------------

Update 12/2/2011

I figured I would post a bit of an update, and try to compile some of the content of this thread into the OP, so that people don't have to read so much. After looking through it all, I couldn't decide what to pick. So my suggestion is to take this as a guide on how to flat hop your bucking, and then skim through the thread (or read through it if you are really interested) and make your own nub.


Your generic 2 piece M4 hop up, pulled out of a KWA SR-5.


Pull the barrel out, pull the bucking off the barrel. Taking the hop up apart is unnecessary, but I generally rebuild them whenever I work on them.


You'll need a pair of pliers, something shaped like these.


Stick the pliers in about like that. Then you are going to want to open the pliers a bit, and fold the bucking's lip into the grasp of the pliers


About like this.


Now you will carefully pull the bucking through itself using the pliers. You sort of slide it along. Be careful and don't go fast, you don't want to rip the bucking or damage it.


Ta'Da. An inside out bucking.





Then, using some sand paper, a dremel, nail clippers, your teeth (probably a bad idea) you'll want to remove the inner ridge (the first picture), and the inner mound (the third picture). I used to simply hold the bucking between my fingers, but others have had success slipping the bucking over the non hop up end of the barrel, so you have a hard surface to sand on. I used a dremel, so I didn't quite have to do that, but it is very helpful. Just be careful to not sand through the bucking. You also want to try and sand as little as possible of the insides of the bucking.

Then, wipe it clean, soap & water helps, and then flip it back right side out in the same way you flipped it inside out.

Alright, now put it back on your barrel. Generally I hold the bucking, and put the barrel in upside down, with the hop up window on the bottom. I do this so that I can see what the inside of the bucking looks like, and know that it's going to have a smooth part of the bucking that makes contact with the bb.


A bad contact patch.


A good contact patch.

See the difference, one is smooth, and that smooth part is what you want over your hop up window, not the rough side of the bucking.

And, for some help finding those particularly helpful threads on making nubs, here are some links to posts throughout this thread:
Kamikaz3 review of the flat hop
Starting at this page, and continuing to the next has lots of good pictures and ways people have made their nubs.

This post has been edited by Star_folder: Dec 2 2011, 09:53 PM

This sounds really interesting. Like really really interesting. I might try something like this by taking one of the stock brass barrels I have laying around and lengthening the said window and maybe custom form a nub similar to that of the Firefly buffer rubber and see what I can do. I think I may go out and buy some buffer rubbers ASAP too judging from what I've heard/seen. Too bad I have like 10 H-Nubs saved up from a stock-up purchase, but at least they were only like $1 each... I guess I could try crafting my own in the meantime.

Darn you Star! Now I'm going to actually have to use tactics instead of just out-ranging everyone!
Haha, with all joking aside...very nice write up. I'm sad to see the secret is out...but I hope it helps evolve the sport.
This should be pinned.
-Major9

Yeah, well if it makes you feel any better, I don't do this to my loaner guns. If you've got any of those you could just drop the H-nubs into those. A problem with the firefly buffer rubber is that it's $13. Which is kind of the reason I've been trying to find a replacement that is cheaper.

I've actually done the same thing with a few Prometheus barrels. Call me crazy. Only problem is that I'm having some compression issues, I need a new air nozzle. Mine has finally bit the dust. So I'm waiting on that until I can continue experiments.

I was able to test the barrel in a friend's M4, the one one I mentioned in the above thread. To be honest, I couldn't tell that it helped much, however, it may have a better effect on a gun that shoots a bit hotter.

*edit*

lol, well with you and buppus going around telling people to do stuff similar to it, I figure I might as well bump them the rest of the way, if they can cleanly remove the inner mound, they are already half way there.

Honestly, I wasn't going to bring it up for a bit longer, until I did some more experiments, but I guess you guys just drove me to it. And you've still got your outrageous rps to give you a step above the rest. Besides, there are still tones of other mods done to the guns I above mentioned to get them to shoot that accurately. People still have to do their research.

lol, If I pin it, then it really will start to bring attention.

woah this is awesome Im going to try this later this summer for sure.

Well...it should be pinned because of the useful info. That being said, nobody reads pins anymore...so it wouldn't really matter.
And I do recommend this method...but only to the few people that actually ask

As soon as I start my DMR project I'll be sure to try this. Good article, now the secret is out (sadface). I remember those discussions.

This post has been edited by The Jam: May 31 2011, 06:53 PM

When I saw that anecdote about the 200ft shots at 1j I literally dropped everything and ran to my work table to open up my CYMA AK.

Any way, if we are trying to maximize contact area, would it be advantageous to file the barrel window to make it wider?

lol, man, are people really this upset that I've posted this? Should I just have kept it a secret until the word got passed around so much that we all "secretly" knew about it but wouldn't publicly tell anyone?

The way I see it is the only way to advance is to share information. I kept it secret for long enough. It requires a bit of skill and dedication to be able to do this mod, maybe not as much as other mods. But if a person is willing to do the work, then, I would assume, they are responsible enough to not abuse the power, so to say. I guess I've been part of the open source community too long for my own good.

*edit*
dang it I've got to write these posts faster...

Served, If you'll notice above, I've already tried this on some Prometheus barrels and Kamikaz said he was going to try it on some stock brass barrels. And it's not a wider contact with the bb that's important, but a longer contact with the bb. The longer the bucking has to contact the bb, the more stable and consistent the hop will be applied to the bb.

I guess I should also note about that gun, like I said before, it was very much a modded to be a DMR. Barrel stabilization, hop up shimmed, floss around the bucking, teflon around the cylinder head, the air nozzle is a little leaky, but not much I can do about that without getting a new one, and it also has a new piston o-ring. It chronos about 280 +/- 5fps with .28g bbs. Which are what I used to shoot out to 200ft. And, just because they could reach out to 200ft, doesn't mean they didn't take their time doing so.

Also, something else I've found is that because of the longer hop up contact that the bb has, it does decrease it's muzzle velocity even more so than normal hops. From what I've seen, it's 20-30fps drop with the hop up on and properly tuned to the bbs. My L85 has a .2J difference between hop up all the way up and all the way off. You can do the math yourself on what that equates to a 30fps difference.

I for one was kind of half sarcastic when I said it. This really is the only way to evolve the sport. Kudos for doing so. Your average joe won't install this anyways...only us power hungry freaks

This post has been edited by major9: May 31 2011, 07:36 PM

Nice writeup! Not sure if this is pinned or not yet, but it should be. Again, nice job.





POWERRRRRR!!!!!! UNLIMITED.... POWERRRRRRR!!!!!!!

I loled quite heartily. I usually don't quote pictures, but I love star wars, so it's getting quoted.

And, um, to prevent this from being a rank post... ah... ... oh, I'd like to thank Soccer again, I talked with him a lot about this mod, and he gave me some good ideas, and I enjoyed talking with him about it. I talked with him so much I don't feel like I gave him enough credit in the first post.

Great write up buddy, even If I did tell you not to open source it :P I liked being one of the few non airsoft techs to know the "secret"

Pin this bad boy!

Thanks for clarifying, Star_folder.

Now, can we get some shooting videos form some of the people who have successfully implemented this method? I'm sure I'm not the only on who would like that.

If I had a video camera, I could do it, but I don't. I also don't quite have the range I need to show how far these bbs can go.

Also, 17 Delta brought up a good question. There are three variants of the Firefly nub, soft, normal, and hard. I couldn't really tell a difference in test results between the normal and hard. But I only use the hard nubs in my tests if that tells you anything.

I was just about to ask the same thing. This sounds really interesting and I plan to experiment with this once I get out of school. And just to clarify since the Firefly nubs are somewhat pricey at $13 a piece, which one should I go with for with 450 ish fps? I'm thinking the normal one, but I'm not sure.

Since Star has decided to open it up, I guess I will include such an item in my advice giving...

anyways....use the Hard type


I am not sure how it works under full auto though....I imagine it will be eaten up a lot quicker than a normal bucking...by a lot.....

Warnings:
You will most likely go through your buckings much faster due to the amount of friction due to increased surface.

You will also need to clean it more so because the increase in that will make heavier bb's rub off even more and since this modification requires high friction..letting that residue from the bb make it smooth will greatly reduce your range.

Also, Star had a nub actually crack on him, NOT the bucking..the nub...so at a high fps these things take a lot of shock and will most likely crack.

Seeing all the above warnings I can say this to sum it all: with this modification you will greatly increase your range but the increase comes with a high replacement ratio. Be prepared to continually replace the bucking/nub

Your AEG needs to have a high fps to achieve insane range with the very heavy bbs which, in most cases, makes it non field legal. Please keep this in mind when skirmishing that though you may be able to increase range, cheating reduces whatever "skill" you think you may have acquired by using this mod.

Case in point, use the mod....use legal fps. Play and have fun.

This post has been edited by soccer77: May 31 2011, 10:16 PM

I would say the hard nub. But I'm not entirely sure it makes a difference. Like I said, it's the same nub I've used in all my set ups.

*edit*
To clarify, the nub that was destroyed was done so because I removed my barrel before I turned my hop up off. It was my fault. However, I wouldn't have taken my hop up apart if I hadn't of noticed a decrease in accuracy. So I can't really say how much beating the nub takes, as I screwed up looking at mine.

My KWA, I really want to acheive results like you had. Except my gun shoots around 340ish fps. And you read my post and you know my nub is missing.
So this I what I have:
KWA 2gx hop-up and bucking.
I don't really want to spend money on a prommy, but will a brass barrel work with the buffer rubber?

Also I don't really know where the buffer rubber goes. And what do you mean, inner ridge removed? There is the bucking on the barrel and a nub or rubber spacer that touches the bb, thats all I know. Please enlighten me.

This post has been edited by KWAboi1: May 31 2011, 10:33 PM

The Buffer Nub goes in the same spot that a normal nub goes, If you look at pictures from it you'll see that there is a round part on the top of the nub. This part fits on your hop up arm, where the normal nub goes. The long flat bottom part of the nub is what makes contact with your bucking.

The inner ridge is the part of the bucking that is opposite the internal mound. It's long and thin, and goes down the length of the bucking. It fits into the ridge of the barrel that is opposite the hop up window.

To be honest. After doing the experiments on this bucking. I can't tell the difference between brass, steel, high quality, or low stock barrels. I got the same results with a crappy aluminum stock barrel as I did with a Prometheus barrel. Now, I'm sure if I took a target, and measured it out, the quality barrels would give better results. But judging it by eye, the results looked the same. You will be fine with your stock barrel.

1. take out your bucking and flip it inside out and sand down the rubber parts that protrude
2. install the buffer nub into the hop up arm
3. put in a new o ring to fix your lower fps (unless you just put in a weaker spring and want fps like that)
4. close it up and use 0.25g bbs and you should get 240ish feet in range...just a guess? I haven't experimented with different bb weights and fps.

So I plan on ordering from Airsoft Atlanta, are they good?
BTW, which firefly buffer rubber do I get, hard, normal, or soft? I still can't really understand you because I don't know all the parts. Can you refer to this KWA picture diagram for me?
http://www.kwausa.com/forums/index.php?showtopic=493

What is a substitute for an O-ring to fix my lower fps? Electrical tape? Rubber bands?

The O ring I am talking about goes onto your piston head which is attached to your piston. They wear out after awhile. 14# is the correct size you pick up a pack of 10 at your local hardware store for cheap.

KWA's in their stock form have excellent compression due to the proprietariness of their parts so I am assuming its the Piston O ring.

Anyways...the hop up unit...is the part that is attached to the barrel when you open the gun.

You disassemble it (there are many guides just look at youtube) and follow what I said.

This post has been edited by soccer77: May 31 2011, 10:53 PM

Stupid internet...sorry mods...Double posted on accident.

This post has been edited by soccer77: May 31 2011, 10:52 PM

I'm assuming this modification yields much better performance than a KWA 2G or PDI W bucking?

For an AEG shooting around 350-400 fps with a ROF ranging from 15-26 rps, do you still recommend the hard type buffer? Will using it in an "assault" AEG cause buckings to wear out quickly? Is this modification better for DMRs since they are typically restricted to semi-auto?

Do you happen to know if a Madbull 6.03mm barrel needs the hop up window "adjusted?"

Awesome write up.

I need to pick up a dremel....

My o ring is fine. My KWA has seen under 2,000 rounds. All my questions were pertaining to the hop-up.

Personally I think it works best in DMRs as does the original G hop.

I think you can use it in autos but I believe it will wear out in a high rof setup and in autos twice as fast as a DMR and even then the DMR will wear it out a lot faster than say a normal DMR setup that we would use today....You are squeezing the bucking pretty good between the buffer and the bb and its rubbing across the entire bucking rubber multiple times....this concept lives on friction much more than say an SCS. So yes I would say it will wear out a lot faster.

Consider it something that its dangerous when used but requires replacing a lot, though I have not gotten to that point mainly because its not being used in my auto setup. It may take a bit of time to notice a loss in range that and if you use it all the time its harder to notice in an auto setup that its actually weakening.

Err I don't know. I have a Madbull barrel handy but from what I can see it looks...ok but that's just at a glance. I don't have any spare buffers on hand. I just ordered 3 more.

I just use sand paper.

----

EDIT:


Well you are getting very low compression for that gun then..

My KWA bucking fits tightly in its 2gx hop up chamber and after testing its compression a teflon tape/dental floss mod was not needed. You can still do one if you like.

EDIT 2: I said this earlier...in case you missed it.



This post has been edited by soccer77: May 31 2011, 11:16 PM

This is an sr5, KWA makes an extra port on the cylinder to let out air. Fps on a sr5 is between 335-350, around 350 new, but its broken in now, so about 335 fps.

This post has been edited by KWAboi1: Jun 1 2011, 12:42 AM

I found out that in my zeal to avoid overstating my success, I was actually underestimating my distances. What I was calling 200' turns out to be more like 275', so with my Mad Bull red, and 375mm PDI 6.01 shooting at 1.85J, I'm getting pretty impressive results; though as you said, not as impressive as soccer's or star_folder's.

I am wishing I had gone with the prommy ASH 6.05 instead of the PDI 6.01, just because of the barrel window issue - my flat nub looked more square than rectangular becuase the window is so short.

I may also try some barrel window lengthening experiments on stock brass barrels I have laying around - I'll definitely post the results if I get around to it.

As for the hardness issue - my thought is that softer would be better, as there would be less reliance and strain on the bucking since the nub would flex and participate in maintaining an even stroke as the BB passes through. In fact, we may be able to combine the strengths of the G-hop strategy with the strengths of the SCS strategy by going with softer flat nubs. I may try some lower-durometer material in future experiments as well.

My apologies then.

I assumed an M4/M16 type KWA.


It should still work good.

A key part to this hop up mod is finding a bb that can handle the backspin from the flat hop. It sounds trivial and standard but seriously....it really matters.

I would start AT 0.25g for your gun. 0.28g or 0.25g would work best for your fps and this mod. I would test both.

EDIT:


I have not tried the other Fire Fly Buffers, neither the soft nor the normal. They may work better.

I agree on the concave part.

krap101 is on the UIUC team with me. the "Pad" idea stemmed off of me mentioning the g hop to him.

Its the plan that a concave long nub be created and its the process of being cnc with a flexible item attached to it.


This post has been edited by soccer77: May 31 2011, 11:30 PM

Just ordered hard firefly buffer rubber from Airsoft Atlanta. Looks like my guess of hardness was correct. My m16 shoots 460 fps with .28s. Starting off with a systema bucking, then try some alittle harder. Have a hard dream army bucking from kmountain. Will report results in few weeks.

@ Buppus
I have:
A KWA 2gx hop-up and bucking
Original TBB
The buffer rubber replaces the nub or rubber spacer right?
So if I just buy a firefly soft buffer rubber, I'm good to go?

Shopping list:
Prommy ASH 363mm barrel
Firefly shot buffer rubber

@ soccer
I have a TON of ASGI .20 bbs I won at the Black Friday sale. Should I just sell all the bags and and buy .25s?

This post has been edited by KWAboi1: May 31 2011, 11:44 PM

I have done all the compression mods that I deemed needed and then some.

I have been very busy irl but I would say...mid to late June I should have it finished and I will review the completed DMR and Buffer nub in it for you though by then someone will beat me to it.

I will post it anyways with pictures and measured shots. If I can get my hands on a video recorder I will add that to here as well.



This post has been edited by soccer77: May 31 2011, 11:58 PM

can someone please answer my question ^^^

@ Buppus
I have:
A KWA 2gx hop-up and bucking
Original TBB
The buffer rubber replaces the nub or rubber spacer right?
So if I just buy a firefly soft buffer rubber, I'm good to go?

Shopping list:
Prommy ASH 363mm barrel
Firefly buffer rubber

@ soccer
I have a TON of ASGI .20 bbs I won at the Black Friday sale. Should I just sell all the bags and and buy .25s?


All I need to do is put where the rubber spacer or nub would be, put a firefly buffer rubber. When I looked at it, the shape seemed so different. Will it fit without any mods done to the hop-up chamber?

This post has been edited by KWAboi1: Jun 1 2011, 12:46 AM

Get 0.25g is my suggestion. You can try a few real quick and test the 0.25g next.

The buffer nub replaces the nub. You could try the soft buffer, let us know how it works. I have never used it

I'll let you know the results. I'll be heading to ASGI on the sale so hopefully I can snag a prommy at a good price. The nub I'll order from airsoft Atlanta. I might just try a normal strength nub. I don't want to find that the soft nub Isn't giving me the results I want.

Can some one be so kind and please measure the unit and paste a large picture of the thing :) (in metric please)
I can make a 3D image of it for use on a 3D printer. I will post the STL files, so that everyone can make their own flat nub.
After that there is a possibility of adding a concave desing to the nub.
(pardon my english, it's not my primary language)

(a quick drawing :) )


This post has been edited by Collat3ral: Jun 1 2011, 02:27 AM

The Firefly nub will fit into the nub window of a hop up unit unmodified. It's a drop in upgrade.

Collat3ral, The only problem I see with your design is that it will be hard. For a hop up to work right, the nub has to be able to give as the bb passes underneath it. However, what you have there is the exact design I wanted krap101 to build for his experiments. I'm curious to see if it helps out any.

<AT>buppus. I guess I'll have to pick up some of the softer nubs and test them at different fps, see if there is any change in the range/accuracy.

So, I'm curious. Is the general consensus to go with the prommy 6.03 or the 6.05 ASH?