SPeaking of which (firing pin), they appear to be replaced with a slightly beefier pin in new USP's. I have a bunch of spare parts (extractor and extractor spring, firing pin and springs, firing pin block and spring, roll pins, hammer spring, flat spring, followers). Only thing I have had to replace is the firing pin. I have replaced followers, but you can get away with just sanding out the rough spots/chips. My recoil spring in worn in well, but not in a bad way. Just make sure the gun is lubricated with gun grease of some sort in the proper spots.