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Compulsive Reload

Kwa USP match, slide not locking after emptying a mag, sometimes misfires

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As per title, usp match doesn't lockback upon emptying a mag, does however lockback if i insert an empty mag then fire. Can misfire also, lets say maybe 3 bullets out of a mag.

 

Noticed the top of the mag has a bit of a piece missing if that may be the issue, spring also feels a bit stiff to pull down.

 

Thanks for help

IMG_20190511_183741.jpg

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Try loading three or four bb’s and fully fill the mag, see if the mag locks back then.

 

Typically with GBB pistols, but not always, the bb follower comes through a gap in the side of the mag once the last bb has been fired and then this pushes up the slide catch which locks the slide.

 

Sometimes there isn’t enough gas in the mag to push the slide all the way back after the last bb has been fired on a full mag.

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6 minutes ago, rocketdogbert said:

Try loading three or four bb’s and fully fill the mag, see if the mag locks back then.

 

Typically with GBB pistols, but not always, the bb follower comes through a gap in the side of the mag once the last bb has been fired and then this pushes up the slide catch which locks the slide.

 

Sometimes there isn’t enough gas in the mag to push the slide all the way back after the last bb has been fired on a full mag.

I'll give it a whirl tomorrow and report back as it's too late to be firing now lol. Cheers.

 

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On 13/05/2019 at 22:36, rocketdogbert said:

Try loading three or four bb’s and fully fill the mag, see if the mag locks back then.

 

Typically with GBB pistols, but not always, the bb follower comes through a gap in the side of the mag once the last bb has been fired and then this pushes up the slide catch which locks the slide.

 

Sometimes there isn’t enough gas in the mag to push the slide all the way back after the last bb has been fired on a full mag.

Seemed to work after that, but after a few mags it started not locking back again.

Guess that's just the way it is? 

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3 minutes ago, Compulsive Reload said:

Seemed to work after that, but after a few mags it started not locking back again.

Guess that's just the way it is? 

 

Possibly, possibly a slow leak in the mags?

 

Dunk them under water and see

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11 minutes ago, rocketdogbert said:

 

Possibly, possibly a slow leak in the mags?

 

Dunk them under water and see

I'll have a little go in abit and see ta. 

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1 hour ago, rocketdogbert said:

 

Possibly, possibly a slow leak in the mags?

 

Dunk them under water and see

No bubbles, as I say its fine once I fill the mag up then after a few mags which weren't even full it stopped locking back, filled it up again then it locked back again so the gas thing is definitely an issue. 

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I have the same issue with my g26 (couple of threads below yours ) "Issue with G26 (marui) not cycling and firing properly". It's definitely not the magazine.

I have already changed few parts with no results. I'll try this week end swapping more bits and see what's going on. I'm trying a process of elimination.  

 

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On 15/05/2019 at 21:11, rocketdogbert said:

 

Possibly, possibly a slow leak in the mags?

 

Dunk them under water and see

Done a few tests one after the other. 

 

Tested a few more times,

1.Locked back, no misfires
2. Didn't lock back, no misfire
3. Refilled mag, locked back no mf
4 didn't lock back no mf, gas was actually emptied, and slide was freezing cold. 

Seems like the mag is guzzling gas and the slide will only lock if there is enough gas in it.
Christ this is getting on my tits, any idea what the issue is, the mag maybe? 

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Just poor gas efficiency by the sound of it. 

 

When you say you refilled the mag, you mean with gas as well as BBs yea? 

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49 minutes ago, E21A said:

Just poor gas efficiency by the sound of it. 

 

When you say you refilled the mag, you mean with gas as well as BBs yea? 

That is correct, not a full mag though. So is the magazine the issue, or? 

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9 hours ago, Compulsive Reload said:

Done a few tests one after the other. 

 

Tested a few more times,

1.Locked back, no misfires
2. Didn't lock back, no misfire
3. Refilled mag, locked back no mf
4 didn't lock back no mf, gas was actually emptied, and slide was freezing cold. 

Seems like the mag is guzzling gas and the slide will only lock if there is enough gas in it.
Christ this is getting on my tits, any idea what the issue is, the mag maybe? 

 

If you did all this with the same mag, it’s efficiency and freezing.

What I mean is, it might just be crap efficiency and freezing.

 

You could try an Icepick valve in the nozzle

 

 

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1 hour ago, rocketdogbert said:

 

If you did all this with the same mag, it’s efficiency and freezing.

What I mean is, it might just be crap efficiency and freezing.

 

You could try an Icepick valve in the nozzle

 

 

I see no worries, ill have a look. Cheers

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How fast are you firing these shots in this test? What about ambient temps when doing these tests? I own a KWA USP tactical and find the gas efficiency to be pretty good, However like all gas guns, cold weather had a huge impact on efficiency, and performance tends to be pretty awful when the weather ain't so warm. If you are mag dumping in these tests you may not be allowing enough time for the gas pressure inside the mag to build enough to complete a full cycle, allowing the slide to come back far enough to feed/lock the slide. The fact that the slide (and likely mags) are freezing cold points to this. Add to all of that the the temps outside aren't particularity great this time of year, so you're not gonna see flawless results from a gas pistol. 

 

There is a mod that involves adding an o-ring to the rocket valve to help towards improving gas efficiency, the link is https://www.reddit.com/r/airsoft/comments/1pqbtg/simple_mod_greatly_increases_gas_efficiency/

 

There is a link in the post to an Imgur album that gives you step by step instructions, I did it to my KWA USP years ago and it's still working great, I can't say that it's improved it massively, but In my opinion it's helped somewhat. 

 

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