KWA USP tactical cycling issue
 

I have a BNIB KWA USP Tactical that will not fully actuate.
(The warranty is no longer valid)

It has pretty much sat around in it's box, and has had less than 10 magazines through it. It has fired 2 magazines normally since I bought it, and that's it. The gun has been run on green gas, and BB Bastard 0.25g BBs.

It does not fully actuate, it does not have the snap or kick it should, and sometimes will not blow back far enough to even load the next BB. It acts like a gun that is running out if gas (yes the magazine holds gas perfectly, and is properly filled each time). Several bottles of green gas have been tried with the same effect. The gun has been properly cleaned and lubricated, and the hop up is backed all the way off during these tests. I have compared it visually and functionally to other KWA USPs without any differences being observed. I assumes that the knocker/firing pin was not opening the valve on the magazine all the way, but it functions properly.


Has anyone had a similar issue, or has extensive KWA USP experience?

Thanks.

What kind of oil are you useing with the propane when filling the mag's.?

Silicone oil for cleaning, and the lubricant that comes with it for lubrication.

check nozzle for cracks?

It sounds like it's doing what mine was; I had to replace the BBU.

The there was a dead O-ring, but instead of going for a 5 year find the right O-ring and get it in there I just rang up KWA USA.

Thanks, I'll check that out.

Well I did a magazine rebuild just for the hell of it, and it was fine, if not a little dirty.

Next I decided to check out the piston, as mentioned above. Two days ago we were sighting our guns in and I decides to bring my USP out because a potential buyer was going to be there. My friend and I noticed that when you racked the slide back, exposing the breach, that the piston stuck into the hop-up. It would ecentually snap back into place, but we thought it was odd. We had a brand new KWA USP Compact there to compare it to, and although not exactly the same, internally they are almost identical.

As I dissasbled the piston, I found no wear, no burs it could get hung up on, no cracks, no dried out seal, everything good. I did notice however that the small set pin that goes through the piston head, I imagine to keep the guide in place, was protruding from its hole. I cleaned and re-lubed the piston, and reassembled it making sure the pin was pushed properly into place. I'm assuming that the pin was getting hung up on the edges of the slide, and stopping the gun from properly cycling. Unfortunately it's too late here to test fire, I'll have to do it tomorrow. I will post my findings.

That happened to my Mk23 after a game...I switch to stock nozzle and it started firing normally again /shrug

Was the pins the issue? Did you find anything else as potential problems?

I think you need to change a new loading nozzle. Check it out!
http://www.tokyo-model.com.hk/shop/k...7.html?cPath=0

The o-ring can be bad without having any noticeable faults, the only way you can be sure is to do a compression test on it, kind of tricky but it can be done

Yes, the piston o-ring.

On my USP, the o-ring was undersize, letting gas blow by it. Simply install the o-ring backwards, and the tightening of the bolt will now mush the o-ring to the diameter needed. You can't fully tighten the bolt, so use a threadlocking compound, to hold the bolt in place.

Gun works so perfectly now. :)

I received two new KWA USPs recently. Both had the problem you described, and both blew out the main blow back seal (part #38). Taking the slide off I just found chunks of the seal everywhere. I replaced it with a KSC seal, translucent green, vs the opague garbage that KWA made.

Same thing happened to mine... I had to replace the BBU
I have 4 USP's btw

The problem cannot be seen because the BBU will look perfectly fine.

I discovered this problem when upgrading my USP Slides to Shooter Design Slides. One gun would shoot fine with the upraded slide while the other was having issues.

I never would have thought it was the BBU because when I pulled it out it looked undamaged so I popped it back in. It was only until I had no other option that I decided to swap BBUs and bam the gun was shooting perfect.

Note: When I say BBU I mean complete internals there. I couldn't pin point the exact part that caused the problem because everything looked perfectly fine.

btw if you love your USP and have no upgraded to an SD slide shame on you :p

here's how sexy these babies look

http://i1112.photobucket.com/albums/...ps8cb759a4.jpg

Damn. Where the heck did you find the tactical SD slide?!