I’ve done it before on a USP. It is not that bad and you have some of the parts already. I bought a gun that was a heavy LEM and converted it. Based on that, I’d suggest you include the trigger return spring too to make sure you have the right spring, but it is a pain to do and not completely necessary. Same with the hammer spring. I think you can get away with the old hammer spring, but it would be best to replace it. Same with the flat spring which is not that hard to replace with the nickel platted one once you have the rest of the guts out.
As you said you need the hammer complete for V1 (50218570), the sear complete (214180), the trigger return spring (50214164), the hammer spring is (50214300 for the USP and 215694 for the HK45), nickel flat spring (215691), disconnector (50214840) and the catch (50219442). I don’t think you need the hammer axle as I believe from what you said you have it. Call Tommy he will fix you up and check the numbers but I believe they are correct. Good luck.
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