View Full Version : USP owners, please help! (Slide lock issue)

October 7, 2005, 12:45 PM
So I have a USP compact and was thinking about trading with a family member for a full-size USP. (Both are in .45 ACP.) When I was handling the large frame USP, though, I noticed what might be a possible malfunction. Ok, basically what I found is that with an empty clip, the slide does NOT always lock on the USP when manually pulled back (i.e. simulating the last shot fired). So I went and fired it, and the slide did lock. I still think it's strange though, because with my Compact, the slide lock springs into place with an empty clip when pulling the slide back manually. With the full-size, it seems to depend on how fast the slide is pulled back or something; it does not snap into place the way it does with the USP Compact. Basically, when I pull back the slide on the USP with an empty clip in the gun, I get the slide to lock about 30% of the time. If I pull the slide back very slowly, then it reduces the chances of the slide locking to zero.

I fired a few clips out of the USP and the slide locked every time after the last shot, but I still think this is weird. Why would the slide not lock when manually pulling back the slide with an empty clip? Is there something wrong with the mechanism, or is this simply a mechanical difference between the USP and the USP compact? Before I make this trade I'd like to be as informed as possible. Thanks for your replies!

October 7, 2005, 02:01 PM
Sometimes the slide stop gets worn down or a piece breaks off which when you pull the slide back manually will show it off to you, but under recoil, it springs into engagement. You might end up one day with a failure to lock on the last shot. It's a simple fix most of the time. A smith could weld up the slide stop where it engages the follower, or it may be simply bent out of the way slightly due to being put in incorrectly. Either way, I think you need to let a smith look at it for you. You of course could simply replace it, but that will cost you more money than having a smith fix it most fo the time and maynot be the only problem you have.

You may find out it is the magazine's fault and not the slide stop. The follower could be having allignment problems as well or part of it could be broken off. It's alot easier to diagnose while looking at the gun than here on the net, but these are some of the more common ailments. One more thing to look at, make sure the slot cut in the magazine is allowing the magazine to ride up fully into engagement with the magazine release button. If it isn't all the way up in the gun when it is empty or loaded, the slide stop won't catch on the follower then either, and sometimes when the mag is empty, it won't be pushed in far enough. See if the magazine moves slightly upward when you press the button. If it does, you should be ok, if it just drops right out, the slot may need to be increased slightly to get a full positive enagagement.

Like I said earlier, a smith should look at the gun for you, he should know what to look for and can fix it quickly for you. Good luck with it.

October 7, 2005, 07:05 PM
Thanks! I appreciate that very expert advice. In the end, I decided that I would go ahead and keep my USP compact, and go ahead and start saving for a good companion for it - like a USP Tactical or perhaps even a Mark 23. Thanks again for the help!

October 8, 2005, 02:03 AM
Replace the magazine spring with a new factory or Wolff.

Problem solved.