Wow,your guns still having issues? Must be a fairly bad lemon from G&G. I have not been active for some time so I may have missed a thread but have you tried delving in to the gearbox and checking compression issue or disabling blowback?
R-hop can be picky to work with since you need to do a lot of modding on the patches,Z-kit make it a bit easier. I hear from some people that an M-nub is also a required mod but I assume you have that already.
Anyway,It would be nice to hear a detailed report back since I hear nothing but good things about R-hop on american forums i used to frequent,and I kind of began to think it was snake oil. I still need to experiment with G-hop myself but right now I have the VSR shooting way to good with the Pdi w hold and do not want to mess anything up.
This is for my Tar 21. I have basically left the G&G T4-18 to be a CQB gun although I need to gear it up for okto in a months time. I have mainly been working on the Tar 21, replaced the motor, the piston and head, the cylinder head, the nozzle. That fixed the airseal and the trigger pull but then I saw how inaccurate the hop was being applied, a G&G green bucking helped but not enough so I started a Z kit R hop into it using an M nub. My first attempt didn't go so well with the overhopping but it was partly the bucking and partly the hop patch, I hadn't quite got it sanding enough. That is now fixed so the issue was entirely my own.
This is what I know about R hop so far (at 350fps):
- My previous hop unit with a G&G green could lift .25g BBs fine, but not a .28g devil, whereas the G&G T4-18 could lift the .28g's OK (so its the hop unit not the rubber).
- The rhop was overhopping a .28g devil impressively, I have bought some 0.3 and 0.32's to test with that as well as I basically need to choose the ammo on the basis of the lift because you can't really change the lift it gives much.
So its better than how the gun came before, and it can apply more backspin than a G&G green bucking, even in the G&Gs decent hop chamber.
What I saw at UCAP was about 20m more maximum range with 0.25g BBs and maybe a little more than that with the 0.28g BBs. But neither was really usable due to overhop and ATPs numbers suggest this are right where I would expect with overhop. So my prediction from where I am is that it will fix my hop inconsistency due to the rubbish plastic hop unit that is in my S&T Tar 21 pro, but it doesn't look like its amazingly going to increase range and certainly not out to 90m as some people are saying it does. But the overhop had my FPS swinging like 10 fps so I can't really predict much from a badly installed R hop.
Edit: I should also mention it took a lot longer than the "10 minutes" suggested on the guides to this even though I bought all the right bits and pieces (including RTV for the glue between patch and barrel). The main reason it took longer was because I needed the middle patch and it had a reasonable gap to the edges and it needed a lot of sanding. With 400 grit sandpaper I think it took about 2 hours of sanding to get the patch down to the barrel. Its partly due to the fine sandpaper but mostly due to the fact that the patch isn't really held in place strongly enough for sandpaper to run over it in an arch. So I had to go back and forth slowly and softly so as not to detach the patch. In the end the first time I called it "good enough" and it ended up overhopping. Now its actually flush but it was another 1 hour of sanding to get it there. I can't say it was quick or painless (I ended up sanding my own fingers a lot holding the patch in place) and the RTV did not say liquid long enough to finish the process so that was a waste of time as I ended up sticking it with superglue (still not strong enough to sand away without concern).
So all in all I have found the process of installing it a bit frustrating. The larger patch was just slightly too tall so I couldn't use it but the medium patch was a bit off. I would have probably been better off with the tall patch and sanding the legs to bring it down rather than what I did. So just be aware of this if you do it to an odd barrel (S&T in this case) like I did.
I also lapped the inside of the barrel and its very smooth and shiny now. I will be seeing the impact of both of these things done together rather than individually, but at least at home against paper at 10m lapping looks like its worth it. My grouping of 1.5 inches looks to be "same hole" on 10 shots (but with fliers due to the overhop) so maybe its 1cm now. I do feel like I am making process making the gun shoot well, the airseal definitely helped no doubt about it I can recommend fixing bad airseal. R hop and lapping not sure on yet.