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Discussion Starter · #1 ·
Hello all, first-time handgun (and USP Expert) owner.

I bought my Expert second-hand, in good shape and all, and owned it a little while now. Initially it worked fine, but slowly it has has started to develop a rather annoying malfunction that makes me unable to use it in competition. Basically what it does is it doesn't always want to drop the hammer on a trigger pull. By that I mean that I'll depress the trigger fully, and the hammer doesn't fall. What makes it very annoying and potentially dangerous is that the hammer may or may not fall if you keep the trigger depressed. I've noticed that when I dry-fire it and it does that malfunction, wiggling the gun or tapping it on the side will make the hammer fall, as if something in the internals gets stuck but wiggles loose with extra movement.

I've checked checked and lubed both the FPB and the firing pin, which are both moving freely. I also took apart everything between the trigger and the hammer up to the safety (couldn't remove it because of the damn tiny roll pin holding the ambi safety in place on the right side) just yesterday, cleaned and lubed every part, and put it back together. Test fired at the range today, with no luck. Same FTF issues. Damn shame too, because the gun's accurate and a pleasure to shoot when it works, but my confidence in it is starting to get undermined. And I should also mention that the hammer doesn't seem to have any trouble getting released when the slide is off.

I had the ideas so far of removing the FPB and seeing how it works after that, as maybe the FPB is for some reason still putting too much resistance on the trigger pull. Might also try adjusting the trigger overtravel screw, see if it's maybe allowing for too little overtravel right now.

If anyone has any ideas or suggestions, they're certainly welcome. And I can supply pictures on request at some point as well.
 

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adjust the OT screw.

Set it all the way in and see if it still has that issue
If that corrects the issue then adjust the screw until it repeats the failure to fire and then back it off a little so it drops with least amount of over travel.

Sometimes the screw unscrews a little
 

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Discussion Starter · #9 ·
adjust the OT screw.

Set it all the way in and see if it still has that issue
If that corrects the issue then adjust the screw until it repeats the failure to fire and then back it off a little so it drops with least amount of over travel.

Sometimes the screw unscrews a little
Thanks for the advice, I'll give it a shot in the next couple of days when I catch a little range time again. I realized I hadn't touched the overtravel screw at all after the previous owner, so it would seem reasonable that it's unscrewed a bit on its own and got a bit touchy.
 
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