KWA KP5 (aka Umarex USP.45) misfiring/seal problem
 

Like many other peoples here, I have misfirings with my USP (all action cycle but BB not exiting the barrel... but droping from it when I shake the gun, meaning that it's still going trought the Up-Hop...)

I tried everything... lubing, complete reassembly, ect ect... was in lot of pains...

Then,

I noticed that the mag was a little bit loose in the grip (maybe around 1mm of so.. not so much). So I tried to shoot while pushin on the bottom of the mag and Bingo ! Worked flawlessly (well, as long as I maintained the pressure on the mag...)

Any tought on what that could cause that ? The mag release lever that got weared up ?

Are you making sure the mag is seated properly with a good smack?
If so, it would seem like the mag isn't sitting up far enough. Is the mag catch worn down? Is this a new gun?

the BB could be jamming in a swollen hopup rubber, then the gun cycles and forces another BB into the chamber, forcing the first one out, replace the hopup rubber

That wouldn't explain the magazine issue/solution.

oops, i missed that part...

Curious if the sear or lip that catches the magazine is worn down or not... Or hell, if you can take a picture of the top of the mag, curious if things are raised/sunken too much.

I find on my USP I have to download the magazine, and also when loading to lock the slide open, insert the mag and then slingshot the slide.

That way I'm sure the mag is seated.

Yea this was happening with mine too ... Except it def. Wasn't a swollen rubber... I was just firing dry propane through and it would do this 6 bb's would jam up and the spit out ... Of course it would do this after three magazines consecutively

This is not a brand new gun, but it's not old either (I fired what, 12-15 mags trought it ?).

During a game, a was able to try it with another mag (that was working for its user) and had the same issue. So the problem is not the magazine... It really seem that something is preventing it from sitting up far enough, as you said Styrak. (I can clearly see it when I push/release and play with the mag inserted but with the slide removed.

I can't tell if the mag catch is worn up, as I don't know is initial apperence/condition but... since it's the only thing in the gun that catch/grip the mag.... it has to be the faulty spot, right ?


EDIT : well,.... 3 mags later the trick of pushing on the bottom of the mag is not working anymore... and if I drop an BB from the front end of the barrel, musket-style, and shoot it work... should be the hop-up rubber then (at least now the confusion is over...)

I heard that KSC and KWA are cross-compatible on parts, is that right ? If so, that part : http://www.airsoftparts.ca/store2/in...roducts_id=356 (KSC Hop-up Rubber - USP/MK23) should work... right ?

KSC and KWA are compatible yes.

I warn you, when you switch the rubbers, be careful not to lose the ball bearing. It'll fall and be lost to you forever if your not careful.

Well thanks for you help everyones... I gonna try a new rubber and post updates on the case, for the others to know...

I said it so don't flame accusing me of necro-posting ...

Buyed a KSC hop-up rubber from airsoftparts.ca.. did not even fit in the gun (but it could be a mistake about the version of the gas system... like NS2 vs System 7, I don't know).

Buyed another one directly from KWA USA (should have done that first :banghead: ) and it fixed the problem after some lubing.... great.

But after a game and a truckload of sand (cleaned afterward, duh) it started the same behavior again...

... I'm lost guys ...