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G-Hop: Getting the extra reach without going over the legal limits
#1
Over the past weekend, I was trialing a modification I did to my ACR on Saturday. The goal was to try to reach the 60m or beyond even but staying within the Japan legal limits. I thought I'd share this information with you after last Sunday's trial runs.

The idea initially came from seeing First-JP's Quasar and Fortress Web. These mods intrigued me but I didn't want to spend Y17,800-Y21,300 at these shops to do the mods.

As such I asked Airsoft Mechanics (ASM). HS5, a veteran ASM member suggested the basis of these customs came from a chap called Gunsmith Engineer and this particular mod along the lines of G-Hop.

So I attempted my version of the G-Hop as posted in ASM. It's somewhat slightly different from Gunsmith Engineer's since the nub on the ACR is fixed, but effectively the same result. That same article is reproduced here as follows :-

So yesterday I did a quick mod of this on my PDI 01 375mm for my PTS ACR and I had a game play today. Actually I must say that I'm reasonably impressed with the distance. It is greater but unfortunately no marker nor any rangefinder (i.e. purely observational) with my JP friends saying "Sugoi! Good reach!" & BB's weren't flying everywhere too so at closer ranges getting headshots despite my Eotech outta alignment Big Grin. I used G&G 0.28g bio BB's and approx 82m/s resulting in approx 0.96J (actually, varied between 0.96 -> 0.98J).

I'll post pics of my mod after dinner in the next 30-45 mins.

Edit: And almost 2 hours later Big Grin :-

Some steps I did before photo side, as per Gunsmith Engineer :-

1) I took a standard Marui Bucking but with a PDI 01 barrel
- Maybe it's my perception but I find the PDI window is slightly smaller than the Marui inner barrel
2) Cut the standard Marui bucking as in the photo of Gunsmith Engineer's page. Naturally cut something that's the window side (or slightly larger but can trim to size later)
3) Cut the sliced bucking ring to open it up and use some of to stick/glue on either side of the window. This is so that when you do stick the bucking over that window, cos without it you'll overhop. I call it the riser (or spacer Gunsmith's case)
4) Use the remaining bucking material and that will stretch over the window and glue it down to that riser/spacer. Note at this point, a side profile of this, it'll look like it's double layered.
5) Make sure there's enough space in the front of the window (in Gunsmith's picture, oval-ed in red) otherwise you'll get bad grouping.
6) Cut the access and the result it this :-
This is with the bucking glued on.
[Image: G-Hop01.jpg]

7) Here's where I diverted from the Gunsmith's a little for two reasons :-
a) I can't change the ACR nub as it's a nub built into the hop chamber. I can send pics later if you want to see but not relevant to this thread. As such I can't do the nub mod he does later anyway. But the goal is to ensure that the nub pushes on the bucking -evenly- and in a very flat manner - not at a point.
b) ACR's hop is pretty weak and I found I needed to custom further a slight mod to increase hop

So I cut up two squares of my PDI inner barrel plastic box & glued it back-to- back (to make it more rigid). The size is basically the window size (slightly smaller so that it can depress on the bucking evenly). I then positioned it appropriately and glued it on. I had to position this -very- carefully.
[Image: G-Hop02.jpg]
[Image: G-Hop04.jpg]

Outside the hop chamber, there's a little bit of a flat bump visible :-
[Image: G-Hop03.jpg]

8) Back to Gunsmith's mod, I inverted the Marui bucking and -carefully- cut the bump inside as much as possible without punching a hole through the bucking. The reason for this cut is that you don't need that bump inside bucking anymore since the steps above effectively creates that flat bump.

9) I also skipped the nub mod for 7 (a) & (b) above

10) And here's two pictures inside the hop chamber at 0 hop (still a slight bump), and at max hop (somewhat deformed bump - but luckily I don't have to hop much to use full hop) :-
[Image: G-Hop05.jpg]
[Image: G-Hop06.jpg]
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#2
Good job! What kind of glue did you use? And how thick the plastic part needs to be?
Aliis inserviendo consumor.
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#3
I used normal adhesive glue. Note that plastic bit for me is where I diverged from Gunsmith Engineer's 'cos of ACR's somewhat proprietary hop chamber. At first when I didn't use it, I found even at ACR's max hop setting, it was hardly hopping. I couldn't change the ACR's nub 'cos it's proprietary. If you look at Gunsmith's recommendation, he said you could use Firefly Buffer 'cos that presses an even square over the bucking, which is exactly what you want. On the ACR, the nub is proprietary so I can't really use an aftermarket nub (actually I can and done before but don't wanna try that again).

So if you're doing this on a normal AEG, then probably stick to Gunsmith's instead.

Note that all this isn't bedded yet. Even the guy in ASM are 'experimenting' with it. So experiment at your own risk. I've just had good trial yesterday but I'm sure there's more for me to fine-tune.
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#4
Cool findings Q

"8) Back to Gunsmith's mod, I inverted the Marui bucking and -carefully- cut the bump inside as much as possible without punching a hole through the bucking. The reason for this cut is that you need that bump inside bucking anymore since the steps above effectively creates that flat bump."

Don't follow this part. You do or don't need the bump? Essentially you are turning the bucking inside out and trying to flatten it? Then reverse it and place it on top of the inner barrel like usual, hiding the glued sections you have pictured?
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#5
Will this work on stock marui barrel? or just on tightbore barrel?

And how much is the total cost to do this mod?

Thanks in advance Big Grin
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#6
(16-11-2010, 04:52 PM)GingaNinga Wrote: Cool findings Q

"8) Back to Gunsmith's mod, I inverted the Marui bucking and -carefully- cut the bump inside as much as possible without punching a hole through the bucking. The reason for this cut is that you need that bump inside bucking anymore since the steps above effectively creates that flat bump."

Don't follow this part. You do or don't need the bump? Essentially you are turning the bucking inside out and trying to flatten it? Then reverse it and place it on top of the inner barrel like usual, hiding the glued sections you have pictured?
Thanks for the pick up, I've re-edited to say you "don't need the bump anymore".

Hopefully though readers who's actually thinking will know what I mean instead of what I said Big Grin.

(16-11-2010, 05:04 PM)ace5kills Wrote: Will this work on stock marui barrel? or just on tightbore barrel?

And how much is the total cost to do this mod?

Thanks in advance Big Grin
Ace, I'm gonna actually leave it up to you to click on the links and read what I wrote above and spend some time thinking about what's being done here. If you have any further questions after that, PM me.
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#7
Thanks a lot Q for sharing that info, sounds like a pretty good mod. I'll probably try that one after I get my Guarder bucking.

One thing though, got completely confused by that:

Quote:3) Cut the sliced bucking ring to open it up and use some of to stick/glue on either side of the window. This is so that when you do stick the bucking over that window, cos without it you'll overhop. I call it the riser (or spacer Gunsmith's case)

Huh

I think I'll need to ask you more details next time I see you Big Grin
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#8
Edit from Moderator: The following posts have been trimmed & merged from the SCAR-L thread.

on your own, or pay to have them do it?
17,000 yen is steep Smile
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#9
I do it myself...it's this stuff :-

http://www.tkoverkill.com/showthread.php?tid=1181
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#10
Yah, I had read your post and findings about it, but I thought that you might have abandoned it when you found 17 bbs in your inner barrel at BB jungle. I thought you said it was from that hop system you installed, but maybe I misunderstood. A cool mod all the same.
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#11
It's a combo. I was using a PDI 6.01mm...the G-Hop made by Gunsmith Engineer was with a stock TM barrel. I'm doing a 2nd with a TK twist. If this works, I may look more towards big bore inner barrels.
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#12
I did the mod with Firefly Buffer on my M16. We will have a game this sunday and I will try it out.
Aliis inserviendo consumor.
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#13
So .... I made a test today. I couldn't measure the distance but it is better than it was with a normal hop-up and the trajectory is better....more straight and hop-up adjustment is more.....how to say.....mmm....precise. As I am using it in a marksman's rifle it also made shooting more precise. So I am pretty much satisfied with the result.
Aliis inserviendo consumor.
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#14
That's good. If you have pictures of your mod, that's greatly appreciated.
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#15
I too would like to see your mod. I have been contemplating doing this on my vsr. The extra range would be wonderful.
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