I have 2 USP 40s. Have never had any issues from any style of ammo. 1 of them had 20k+ rounds through it. Have shot fmj, silvertip, hst, tap, golden saber(I don't shoot Remington ammo of any caliber anymore because there is always unburned powder left over). Black Talons and Ranger T's. Blazer brass, and federals. The feed ramps are normally very smooth on HKs. Is there any substantial buildup there?