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L96 Upgrade Problems!

4702 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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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.
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.
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.
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.
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.
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.
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.
So you are saying the more hop up, the more the arc you are getting?

That is very odd. Is the bucking in there properly? What is your current compression like?
The fact that your shots are coming out lobbing is puzzling me. Typically, if you are not applying enough hop, the shots will shoot out at a straight trajectory and then drop before reaching desired target. You then adjust the hop up, and bb will reach out further at a straight trajectory before falling. If you apply too much hop, it will go straight, then pull up before reaching desired distance. NOT come out of the barrel at an arced trajectory.

So with that, my thinking is that it has something to do with improper installation. Get that thing chronoed and we can see if there is any drastic difference in FPS variation, and we can go from there. However, I am unsure how much that will help. But its good to get that info and rule some things out.

The PDI hop up takes a nubbin, and is that big long rubber piece. The G&G bucking takes a nubbin that is much smaller. You said you had that installed? Possibly switch out the nubbins, reinstall the bucking, and make sure everything is aligned properly and then go from there.

Lots of times, when I get issues like this, I like to take it all down and reinstall everything in the hop up. Might be a small issue that is not very noticeable. If that does not work, let me know. Be sure to take your time and not rush. Come back with results, and we can go from there.
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