The first thing that needs to be mentioned is that no matter what your strategy, the little mound inside the bucking that pushes into the barrel window is generally an obstacle to implementing that strategy, because it either disspates or augments the profile of the nub (if you're using H or V type nubs), or for flat nubs like the FireFly it acts like a speedbump when what you want is a nice, well-paved runway.
The thinking behind the SCS as well as H-nubs, V-nubs etc., is that the increased surface area that gets contacted with multiple-point style nubs (or the single center-point) will help impart a more centered spin, and thus yield better consistency. And that strategy does meet with a certain amount of success, but its weakness is the short time period that it's actually in contact with the BB. The result is that you end up with less horizontal variance in your groupings, but actually more vertical variance; I.e. oval-shaped groupings instead of circular ones. This happens because the contact time is so short that you end up with a more centered spin, but a less consistent amount of spin.
The next big move was the G-hop, which went for more consistency via longer contact time between BB and bucking by using a long, flat nub and modifying the bucking so that a long, flat area of the bucking would be pushed into the barrel window. And the G-hop has turned out to be a mixture of wild success with catastrophic failure. It suffers mostly from unreliability because of the material limits of trying to glue tiny pieces of bucking together and expecting them to hold up under tremendous force, as well as user error and other complications. When it worked, people reported getting gains in effective range anywhere form 50-150', and when it failed it caused a lot of grief.
To get as close to the G-hop strategy as possible while avoiding its weaknesses, a bunch of us are now experimenting with what Star_folder has dubbed the "Flat Hop," which amounts to shaving off that internal mound in the bucking, rotating it 90 degrees so that a nice, even part goes into the barrel window, and using a long, flat nub like the FireFly nub. I know I got a noticeable improvement when I switched over from using the SCS nub.
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.
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.
Edited by Star_folder, 02 December 2011 - 09:53 PM.