KSC USP slide won't lock when mag is empty (solved)

[Mr. G36!]

So, I'm not a GBB guru by any means, so maybe it's an issue as simple as the mags needing some lube or something, but basically, the slide on my USP (.45 fill-size, if it matters) suddenly won't lock back when the last BB is fired. It's always been fine except for one instance in the past where the silicone reservoir on my Propane tank dried up without me knowing, and the gun just kinda seized up. A little bit of lube in 'er and the mag fixed it right up, but now it's doing it again, and I don't know why. From what I can tell, it could be the magazines, but the slide doesn't lock regardless of which mag I use (three of them), so I'm more inclined to think that it's some issue with the gun itself.

I know that this isn't a huge issue, but I like when my things work properly, and it's hard to know when you're out of ammo when this happens, so if anyone could offer some insight or experience on the matter, I'd really appreciate it, as I already mentioned that I'm really not an expert on GBBs.

[audi_bhoy]

If you pull back the spring by yourself, with an empty mag, does it locks back? If so, the gun might not be cycling fully back when the BB's fired, otherwise, if you can see trough the ejection port at the place where the little nib on the mag pushes the lock on the mag, it will give you a good idea to see if it does it's job or not.

If you insert an empty mag while looking through the port, and the lock isn't moving, make sure your mag's nib goes upper than the body of the mag, if so, take a look a the lock, it might be worn.

[Aurelien]

I get this on my ksc uspc as well. Occasionally when I pull it back on a empty mag it doesn't stay back, unless I do so firmly. Interested to see what fixed some up.


This is mostly a subscription reply

[kullwarrior]

Mm when you shoot Mage sure push the mag all the way up, it has bout 1mm of play this lead to slow gas release (velocity of gas is not as fast as you can go)
two method to hold
1) CS style use supporting hand hold like a cup style
2) IPSC or ideal firearm, pinking touch the mag base and thumb grab the extesion part of the trigger guard

[The Chad]

My m9 did that and does it after repeated dry fire. I found that i didn't have enough gas in the mag. Try removing the mag and trying again.

[Mr. G36!]

Originally Posted by audi_bhoy

If you pull back the spring by yourself, with an empty mag, does it locks back? If so, the gun might not be cycling fully back when the BB's fired...

Yeah, I just tried it and the slide does lock when I manually retract it, so it isn't the mags and must be the cycling action. I considered the possibility of not having enough gas, but when I checked to see how much was left in the mag, there was plenty, so if it's a gas issue, it'd have to be a case of too little gas being released I would imagine. Could it also be that the slide needs some grease or something? Maybe there's just a little too much friction between it and the frame? It's a metal slide and metal barrel, not the plastic ones, though like I said, it just started doing this recently.

[audi_bhoy]

Your mag catch might be worn then, causing as said before by kullwarrior a leakage between your mag and the nozzle into the slide. You might try pushing the mag upward when shooting it, then letting it sit onto the mag catch to see if there's a change. The seals on your nozzle and mags might be dried too, a little drop of lub on those will surely help.

[fi3re]

Im not a doctor by any means but based on what i`ve read I think its definitely the cycling action not going far back enough.

Its not the slide catch or mag for sure becuase it WORKS manually

perhaps its the recoil springs or spring guide....there is a stronger spring inside the normal recoil spring...(at least on the kwa version) this might be preventing it from blowing back all the way...

[Mr. G36!]

Okay, let's apply an AED to this thread...

...potentially, if the pistol's chamber were out of alignment, even so little as to not affect the BB from firing, could that disrupt the cycling action? See, I haven't been able to get my hands on a Hop-Wrench, so I've been using a multi-tool to play with the hop-up. I have little doubt in my mind that, changing the dial in this manner, would easily pull the chamber up or down, as when I initially attempted this, it pulled the chamber up and the slide would no longer even be able to return into place, and BBs wouldn't load into the chamber. When I corrected this, perhaps I pulled the chamber down too much, and though the BBs load and fire fine, perhaps something else was thrown off-kilter? I dunno...it just makes no sense to me why it'd be fine and then suddenly mess up one day. There's gotta be a reason...

[Mr. G36!]

Just an update, for any who might be interested. At the last game, I did indeed tinker with the positioning of the chamber, and now the slide locks back flawlessly once a mag is empty (tried with all three of mine). So in the future, if your KSC USP seems to cycle fine but the slide won't lock upon emptying a mag, the chamber might be out of alignment. I know that if it's been pushed upwards, the action won't cycle at all (I had the problem before, and when I fixed it, this one popped up), so I guess if it's too low, it won't lock the slide back when a mag is empty...talk about splitting the atom, ha ha!

Anyway, I don't know if that's was actually fixed the problem, but it's the only thing I did, aside from wiping the slide rails a bit, but they weren't dirty or anything anyway, so I doubt that it did much if anything at all.