I would suspect the 200gr SWC lead reloads might be the problem with your USP, Smithwr3. Give us some specs of this load: OAL, crimped or not, did you do a final resize with a Lee Crimper/Sizer, etc...
Also, check the magazine springs for weight (sometimes factory springs are weak) and any glitches/hangups in movement of the spring/body/follower during cycling. Does the problem happen with both magazines?
With a bit more info, some of the gurus here will discover the problem and provide a solution... FWIW, I am not one of those experts, more a 1911 platform guy who likes/collects/shoots/promotes H&K products in both handguns and rifles. IMHO, H&K makes some of the the world's most reliable and mechanically sound firearms -- they shoot well and don't break when compared to similar weapons. Not always the best in ergonomics - until the recently issued HK45 and P30 - but overall they compete with most of the top shelf firearm producers and in many cases are the standard to which others are trying to obtain...