Love my USP45 Expert. Wanted to buy a NIB 40 Expert but none available. Have decided to buy a NIB USP40 and modify it instead. Trying to duplicate key features of the Expert. Will install Match trigger (best to send to HKCS?). Sights are no problem. Don’t know if it is possible to install...

Hi guys! I am new to the forum and I have been searching for som answers on this topic but could not really find any. I own a USP expert 9mm and it has fired about 6-7k rounds of standard 124gr rounds. So now I was thinking it might be time to replace the recoil-spring and the O-ring (the...