Hey all,

I bought a USP9 full size about 2 months ago and the first 500 rounds went through flawlessly. The brands used during these first 500 rounds were WWB, Winchester Winclean, Independence, and Speer Lawman.

However, the past two times I have gone to the range (using Winclean and WWB) I have experienced FTF. The gun will eject the spent casing but not properly load the next cartridge into the chamber and as a result the slide will not come all the way forward. This has happened around round 60-70 during both times I have gone. In addition, I cant be certain but it seems to happen only with one of the magazines.

What could be causing this?

I doubt its limp wristing as when I first started shooting I was limpwristing badly and it fired flawlessly.

Could it be the magazine springs? I keep the magazines loaded while at home as the gun is also my home defense gun?

Could it be that the magazine is dirty? I have fired about 1000 rounds between two magazines and havent disassembled them to clean them. I have only scrubbed the top portion and the feed lips with solvent and a nylon toothbrush?

What else could it be? Any help would be appreciated

if it's only 1 mag, i would guess it's the spring.  maybe it's gunked up, try givin it a cleaning.

the mags maybe dirty.  
personally i never had a jam with my USP9, and I shoot the same ammo like you, WWB, Independence, Lawman and UMC. But I always clean everything after, including the inside of the mag, even if I shoot 100 rounds.

If cleaning the mags doesnt help does anyone think that Wolff mag springs would make the problem go away?

Quoted: If cleaning the mags doesnt help does anyone think that Wolff mag springs would make the problem go away?

the cleaning should do it.

I have never clean any of my magazines.  

Did you buy this gun new or used?

Quoted: If cleaning the mags doesnt help does anyone think that Wolff mag springs would make the problem go away?

Call HK, get a replacement.

Went to the range today and didnt use the suspect magazine. The gun fired 100 rounds of Winclean flawlessly. To date I have put 1000 rounds through the gun and only had 4 FTF. I know the goal should be zero but I think these 4 were the result of some combination of a flawed magazine, low grip on the gun, and not having my wrists properly locked back.

I think the majority of problems with high quality guns such as HKs is shooter error. This same USP was hitting me in the face with brass until I got one of the range officers to try it. All the rounds he fired ejected perfectly at 3 o clock and he gave me tips on my grip that have completely eliminated the problem.