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L96 Upgrade Problems!

4709 Views 31 Replies 6 Participants Last post by  luke213
Hey guys,

Upgrading my UTG L96 APS-2 has run into a problem: my Angel Custom hop-up unit (which is the exact same as the PDI unit) is causing the gun to totally misfire. The only thing I did not replace is the bucking. When I install the nub and try to fire, I get a dead, flat sound and the BB stays in the gun. I posted a YouTube video to demonstrate the exact problem here:
Without the nub and arms, the gun fires just fine, so I know the bolt system and trigger are all working.

I know lots of people are going to tell me to scrap the AC hop-up unit even though it looks the same as PDI, but there should be a profile difference looking down the barrel with the nub and without it, especially with the gun misfiring. I checked and I can't see any difference. Any suggestions are welcome as I am at a loss for what to do.
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You mean cycling the bolt twice to fire by the first thing? The gun is firing when the mag isn't in because something is keeping that BB from moving on the first shot. I will see if I can put the original hop-up unit back together; lots of it just seemed to fall off when I took it apart and I'm a noob :)

Also, the locking screw that goes into the hop-up unit doesn't like to go all the way in, so the mag catch is a little wobbly. I thought that it would still pretty well keep the hop-up unit secure in the same spot since it still goes into the stock, but maybe I should double check that.

And yes, next time I will be sure and invest the extra $20 in the PDI unit :D
Thanks so much Fuzzy! I got the PDI upgrade kit for the O-rings and saw that their nub was actually bigger than the one that came with AC's unit. I still have the smaller one in and the hop-up was on the lowest setting.

I have never really been told how the bucking is centered (or that it had to be); I rotated it off of what I had been using before the upgrades because I thought it could use a fresh surface :) I did read the sticky thread on the installation which really did help but I don't remember anything about the bucking. Any way you could point me in the right direction?

Another thing, I have the 6.01 TBB for this; will this make the hop-up a lot more vulnerable to this type of problem because of the reduced diameter?
I got a good few shots off after realizing how stupidly easy it is to align the bucking :) That solved the main issue I had up there, but I am pretty sure I still have no hop-up, even after adjusting it pretty far down. I also have some very low FPS for the M170 bolt system I have.

Now I have an issue with the mag catch screw that doubles by keeping the hop-up in place; I stripped it because the hop unit seems to have a bit of a tight fit on there. I'll take it to the hardware store when I can, but with that small of a screw I'm not sure I'll be able to find it there. Any place online where I can buy a replacement screw?
Yep, I found the slit and finally managed to get the gun to fire a few shots depending on how I have the hop-up adjusted. It's really sensitive to hop-up adjustments, probably because of the 6.01 TBB, but I think if I take the time to get the exact right place, it will finally fire correctly!

Thanks for your help guys. I'll post on here if I have any more issues or if it finally works. There's a winter match near me Jan. 11 and I hope to take my rifle.
I still have the stock bucking, I thought I could get away without replacing it but it looks like now I'm starting to have doubts. I'm starting to get hop-up, but it won't give me good consistency.

The bucking seems like it's supposed to fit like it is. What's the difference? (Sorry if that's a noob question, but I have tried to read up on this. I probably failed.) I was thinking for the sensitivity of a TBB I should get a hard bucking, but I will try to look up some AEG stuff.
Okay, so is there a particular type of AEG bucking I need to buy or can I just go for anything? AEG bucking is probably longer.
Great, that should be easy enough. I saw online it comes with a spacer, and some other piece? I'm not familiar with the parts, so are there any installation guides (because I haven't gotten very good instructions from other airsoft parts I buy)?
My G&G bucking arrived and I rushed to install it (I've been pumped about finally fixing the last issue upgrading my rifle, and it's finally going to work). This morning I had enough light to determine how the flight is now, and it looks like the bucking fixed the issue. It flew just fine, although I will of course have to adjust it.

I have one question about the bucking installation: I didn't know what to do with the brass spacer, so I just left it off. Is that just for AEG's, or is that actually supposed to be installed? I have no idea how to install it.

The final gun with upgrades: UTG L96 base
Angel Custom SP170 cylinder system, barrel and hop-up unit with G&G bucking and nub
Action Army trigger assembly

Thanks so, so much for the help Fuzzy! My rifle works now!
The spacer didn't really seem necessary for the gun to actually work, but I still have no idea how to properly install it.

After many adjustments of the hop-up, I'm basically getting lengthened versions of a normal projectile motion instead of the ideal flat trajectory. Is this just a matter of quality or is there something I'm missing?

I will probably be putting some electrical tape on the side of my hop-up arm and hope that's what's responsible for most of the inconsistency I'm getting.
I'm using .28g BB's for now. I haven't got a chrono test in yet but I bought the SP170 spring. I figure I should be shooting just under 500 fps with this setup.

If I add more hop-up, the projectile motion just seems to start at a larger angle. So, I'll get even more arc than I already have with a little more range. I'm far from full power hop, it's just that adding more doesn't do anything that really helps.
Okay, let me try putting more hop on there and maybe I'll get the downward acceleration to zero. Where that happens will probably be a higher trajectory than straight, so I think I may need some drastic scope adjustments to make up for it.

I'm pretty certain the bucking is installed properly. I haven't tested the compression directly; is that the test where you put your finger over the cylinder head? I get really good FPS so far (I don't know exactly how much, but I'm taking this to get chrono'd today.

Does the PDI hop-up take a spacer? I still have no idea where to put it. If I need more hop, though, there's plenty of room to simply adjust it for now.
So the chrono is at about 380-390 with .28's, but it is very consistent, only about 15 FPS range. Since I have an M170 spring, though, I will have to test the compression. Can you let me know exactly how to do that? I got the main idea but I'm not sure how to do it. I'm pretty sure it's the piston O-ring; I had my doubts about it at first but decided it was probably just intentional that the ring was bigger than the piston and didn't fit on tightly.

The hop-up issue wouldn't really have anything to do with the chrono test though, right? As long as it's consistent the hop-up should do what it's supposed to. The nub that G&G comes with is, I believe, the same size as the one that came with the PDI hop-up unit repair kit, but it is also hollow :)shrug:). When I tear it apart, I will reinstall it with the PDI bucking and see if it helps.

So for now, I will do a compression test and if it comes up failing (it will), I should probably get a PDI piston O-ring? What kind of speed should I be looking for with some different weight ammo (I'm almost out of .28's and I want to try some different ones)?

Edit: I went back to the stock spring, piston and spring guide because I thought I would get better compression on that. I can tell a big difference in the cycling just by the way it behaves. It is too late to test it at all tonight though, so hopefully I will have some good results tomorrow.
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I've pretty well taken care of most of the problems I had before, now on to new challenges. I can't get the gun to stop jamming every time I try to fire. I'm thinking the primary reason for these jams is a feeding/barrel problem because now the bolt handle doesn't even make it all the way back in the receiver before the BB gets stuck. When I disassembled the hop-up, I noticed that a piece of the bucking was caught between the BB and barrel and the jams since then seem to be bothering the bucking that goes in front of the barrel. What's going wrong inside my rifle?

Another thing, I started looking for some widener barrels just for the sake of possibly wanting one in the future (and as a possible solution to my jamming problem). After some looking around, I found that Evike apparently sells Prometheus widebore barrels (I have no idea if they actually do). Any other suggestions on a widebore?

Evike Prometheus 6.20mm widebore barrel
For the record, I took care of the jamming problem. Hopefully I will have the rifle firing tomorrow and I will be able to sight it in. The problem ended up being that the barrel and hop-up unit were smashing the "lip" of the bucking (the part that goes over the end of the barrel) into the chamber and blocking the BB from entering the barrel. I cut most of it off and that seems to have fixed the jamming problem, although it is too late to test it, really. More tomorrow.
The AC hop-up is sealed with the two O-rings (it's a clone of PDI), so I don't really expect any problems. It may be the piston head that caused the problem because the original AC one I had to change out had worked fine. Also, if the bucking was getting smashed into the chamber, cutting off some of the lip would only cause seal problems if I cut off too much (a real possibility). Eventually I will chrono the rifle and if I see anything interesting I'll keep this updated.

The bucking is a G&G which has a really good reputation and brand new. If you're talking about before I got the AEG bucking, I was using the stock bucking in the new hop-up unit (oops lol).
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