USP9 double feeding

[Cypren]

I have a brand new USP9 which is demonstrating consistent double feeds (failing to extract spent round) -- initially, maybe once every 100 rounds, but the last time I took it out, it did it twice in 50. It has exactly 1130 rounds shot through it (all Winchester 9mm Luger 115 gr. FMJ Target/Range) and has been thoroughly cleaned after each outing (about every 100-200 rounds; six times overall).

I had a buddy who's an HK armorer (but went through the training a long time ago, and hasn't done a lot with them recently) take a look at the pistol, and he can't find anything wrong with it after a quick inspection. His only suggestion was to send it back to HK.

Before I do that, and lose it for two months or more, does anyone have a suggestion of things to try that I might not have thought of? I did some pretty thorough searching and this doesn't seem to be a common issue -- or if it is, people don't come to forums about it very often -- so I'm thinking I may have just gotten a lemon.

[Kochaholic]

Extractor.

[SIGtrarian]

What Kochaholic said. Using a snap cap or fired case, does the extracter have a good solid grip on the rim? BTW, compact or full size?

[Cypren]

Yeah, the extractor was the first thing we looked at when going over it. It doesn't seem to have any problems when manually cycling it -- the snap caps pop out just fine. Whatever this problem is, it's only occurring during real firing.

And it's a full size, since I didn't specify.

[SIGtrarian]

Does it happen when there are a certain number of rounds left in the magazine, for example, with one or two rounds left, or does it vary. I had a USP40f that would do this when the magazine was almost empty. The magazines, and gun, were new but the problem went away when I replaced the magazine springs with Wolff +10% springs.

[orfeo]

Thanks SIGtrarian, I was just going to suggest mag-springs :)

[Cypren]

Hmm, good thought. I haven't looked to see if there's a consistent number of rounds left when it's jamming. I did cycle magazines to make sure that it wasn't a particular mag that was causing the problem.

If the extractor itself is the issue, does that mean that I'm going to have to send it back? Or can a typical gunsmith make that replacement if I get the parts ordered?

[orfeo]

Take one mag apart and stretch the spring out an additional 35% or more, taking care to keep the coils properly aligned and evenly spaced. Reassemble and test with that mag only. If your problem improves, you need mag-springs. :)

[Cypren]

Out of curiosity, why would a weak mag spring cause the spent round to fail to extract? I can understand why the next round would fail to feed, but doesn't the extractor work on an independent spring that's activated by the movement of the slide?

[robert14]

Weak ammo and /or limp wristing is a regular cause of a FTE in a new pistol with a stiff recoil spring. It was the cause of constant FTEs in my P30 until I started using hotter ammo. Try addressing these issues & see if this fixes it.

[navyman8903]

Yeah im with robert14 on this one, if the extractor is fine then change the rounds, I shot 300 winchester "law enforcement" .40 rounds and they were not the best, they came out down and to the left. They were also lack luster. I would get some 147 9mm ball rounds and see if you have a feeding problem. HK's are blow back not gas operated and are spec'd to take the heavier rounds.

[orfeo]

Out of curiosity, why would a weak mag spring cause the spent round to fail to extract? I can understand why the next round would fail to feed, but doesn't the extractor work on an independent spring that's activated by the movement of the slide?

If you do a search you should find LOTS of info and opinions. This has come up QUITE often. I have theories about the whys and wherefores, and so do others, but stronger mag-springs very often do cure this, and it's worth a try. My NIB USPc 45 had the same problem, and it was cured with Wolff mag-springs. I am consciously avoiding the temptation to to present my theories about why, and trying to just get you to rule out a fairly common culprit the shortest way.

If the test I suggested works, and you then really want me to explain my personal observations and theories about why, I'll be glad to lay it all out there. . . :)

Good luck either way!

[SIGtrarian]

Out of curiosity, why would a weak mag spring cause the spent round to fail to extract? I can understand why the next round would fail to feed, but doesn't the extractor work on an independent spring that's activated by the movement of the slide?I could never figure that out, but when I installed the Wolff +10 springs the problem disappeared. It never really made sense to me.

[Cypren]

I took it down to the range tonight and put about a hundred fifty rounds of 115 through it after stretching the mag springs like orfeo suggested. Not a bit of a problem, although it might have just been behaving well tonight. I'll put some more pressure on it over the course of the week and see how it performs. Thanks to everyone for the suggestions -- really appreciate you guys taking the time, because this had me stumped.

[orfeo]

Its not a fix. . . the springs will revert shortly. It was just meant as a test.

If you call HK they will more than likely be happy to send you new springs, or you could order Wolff +10% mag-springs which will be reliable, but they will be knucklebusters.

[19852]

I had a USPc .45 with the same problem some years ago. Two trips to HK could not solve the problem. Never tried stronger mag springs, wish I had. Had to sell it for something that worked.

[orfeo]

I had a USPc .45 with the same problem some years ago. Two trips to HK could not solve the problem. Never tried stronger mag springs, wish I had. Had to sell it for something that worked.

That's a damn shame, and you're not the only one.

[Cypren]

I'm very curious for your hypothesis on why the mag springs help, orfeo. Care to share?

[SIGtrarian]

With a weak magazine spring, and only a round or 2 left in the magazine, the top round isn't being held very secure. The recoil causes that top round to come loose. This prevents the empty shell from hitting the ejector. The slide moves forward and pushes the loose round into the empty case and back into the chamber, hence, a double feed. That's my theory.

[REWTX]

Thanks to everyone who suggested that the problem could be mag springs. I have a USPc 9 that was just about to go back to HK for FTE, I already have the RA#. I streched the one of the mag springs and ran 250 rounds through it with no problems. During this I ran a mag full with the other one and sure enough 2 FTEs. It really doesn't make sense to me as to why this seemed to fix the problem, but as long as it works I'm happy. It is a shame that HK doesn't install mag springs that work, but the trouble-free rounds through this pistol make me really like it.