I just purchased a used .40 caliber HK USP Compact. When I disassembled it for the first time I discovered it had an uncaptured recoil spring on the recoil spring guide rod. This surprised me. It has the KK mark on the side which from what I gather means it was manufactured in 1999. I also have learned via the internet that early models of the USP had this uncaptured recoil spring - can anyone confirm that this is the correct condition for a USP manufactured in 1999? When did they switch to the captured recoil spring and is there any reason to be concerned about this or upgrade the recoil spring assembly? The spring does not appear overly worn. Thanks any help and information.