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L96 Upgrade Problems!

4713 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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Have you tried loading one bb into your magazine, then racking the bolt back again to fire? Since your gun is firing when the mag isn't in, maybe the hop-up unit is getting moved around by the mag.

Other than that, double check your airseal with your old hop-up to make sure it isn't some other part. Either way, you've convinced me to stay away from the Angel Custom hop-up unit >:D
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
Sounds like the nub and the arm are applying too much pressure when they are installed. Not trying to insult your intelligence, but make sure there is not too much hop up pressure on the bucking, which in turn puts too much pressure on the bb. So make sure that the nub is not too big for your particular chamber. Even if it is a clone, the nub might be too big and causes too much pressure. On mine, I used a nub that was wayyy too big and caused jams exactly like you described.

Have you tried it with the hop up on the lowest setting possible?

Also, be sure that the bucking is centered correctly. Had this issue when I first started with bolt action rifles. Bucking would not be aligned properly and even the slightest misalignment could cause the same exact issues as you.

Hope this helps somewhat. I realize this is a pain in the ass, and will try and help you come up with a solution.
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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?
The bucking can't just be put on however you want. There are slits that have to be aligned properly, so that the window where the nub is pushed down by the arms, is allowed to apply pressure to the bb. Sounds like you said you figured it out, but to clarify, make sure it is aligned properly. It can't just go on any which way.

Also, they will have the right screw at most hardware stores, but it won't be the proper length. I had to have a friend take a couple screws and cut them down a bit to fit properly. I know of no online store that sells the exact size you need, so unless you find one, you might need someone to cut it down for ya.
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.
Just reread your first post. When you say you are running the AC hop up without replacing the bucking, are you using the stock bucking or an aftermarket AEG one? I believe the AC hop up uses AEG buckings and stock l96 buckings are not the same.

Just making sure to tackle all possible issues. Disregard if its the AEG bucking in there.
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.
PDI hop up chambers use AEG buckings. If this is indeed a clone, then it will need an AEG bucking. Hold an AEG bucking up against a stock l96 bucking and you will see the difference in length immediately. That is probably why you are having such major issues.
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.
Most AEG buckings will work. I ran the G&G soft bucking with great results. I have also used Prometheus, KWA, Guarder, and a few others in the past as well.
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)?
The nub that comes with them can be used, but they are much smaller than the PDI nub. Can't remember which one I used as this was over 3 years ago. Installation is the same as any bucking, and need to align the slit up on the inner barrel. Make sure it is aligned properly, put in the nub, and check to see if even pressure is applied through the window.

This should fix your issue.
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!
If memory suits me right, I left the brass spacer out. I believe it is for better compression, but I just stuck to DIY mods on that one.
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.
Well what Bb weight are you using, and what FPS is it shooting (I know these are new by questions)? It may have to do with the Angle Custom parts (hop up unit) because their barrels aren't bad.

Edit: My friends SD97 I now own use to not be able to hop .3's stock. They would have this wierrd 1/2 hop an get like 150 foot range. Maybe you need to apply more hop to be applied thus allowing you to get your full projectile range.
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.
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