Hello,
i have also had trouble with my .40 USP having occasional jams ( 1% to 2% ) It has been back to the factory X2 still no improvement. It jams ( failure to return to battery completly ) with all types of ammo ball and HP. The factory said I was probably limpwristing it. Funny I have no problem with my Sigs, Paras, Glock, Berratta and I am used to a J-frame .357
I have relagated it to the " fun Gun " status but woulod not mind sending it out if anyone knows a smith who does good work on HKs ( Even though it has this problem I still like the gun very much )
Regards
NukemJim