A customer came to me last week with his USP .45 Compact he had just gotten it back from HK who had replaced a broken trigger bar. It has fewer than 1K rounds through it, and is well taken care of. He asked me if I would trust a pistol that broke, and was fixed by the factory. I said no. He asked me to run 500rds through it and see what happened.
I took his pistol and 8 magazines, My 21 and 8 magazines, and 1K rounds of ammo.
Both pistols were field stripped and blown completely clean and dry with compressed air.
2 mags were emptied in clean condition to make sure everything was fine.
For the fist comparison I threw a couple handfuls of play sand in a bucket.
I took each pistol, full mag, round in the chamber and shook it in the sand for a few seconds. I did this first with the 21 and it went bang 13 times as expected.
I pulled the USP compact out of the bucket(it was loaded but decocked), pulled the trigger, hammer falls but no bang. I pull the trigger again and still no bang. Not a squib, and not a delay. I cycle the slide and eject the cartridge, but it fails to go into battery. I repeat, while shaking out sand, until the magazine is empty. After removing the slide blowing the frame out with compressed air I repeat the test.
Back in the bucket, shake, attempt to shoot Ė exact same results. Field strip and blow out with compressed air. This was attempted 4 times, with 4 different magazines. The first shot did go off once, but did not lock up for the following round. Again it required fieldstripping to function.
OK, it doesnít work in sand. For a different twist, I took a UPS mag and a glock mag and threw them in the bucket and shook them up.
I picked up the 21 mag, loaded the pistol, pulled the trigger 13 times. I then picked up the USP mag, pulled the trigger once and it went bang. The slide failed to close on the second round. Ejecting the 2nd round partially inserted the 3rd but also a bunch of sand. The USP mags have basically a shovel extending for the slide stop, which proved them useless combined with the sand.
Sand is over, time for good old potting soil. Potting soil was basically a repeat of the sand. The USP never went bang once. Even with a round in the chamber, and numerous hammer strikes, nothing.
Cycling by hand ejected round, but would not lock up on the following round.
After that we gave up, on the USP and took turns emptying the several full 21 mags.
Iíll return the customers pistol and his 500 rounds. This USP compact went bang every time clean, so it works fine. I would never trust it though, as a carry piece.