Hello.  I had a thought...it would not be cost effective for HK to manufacture "two" different types of magazines (10 rnd and a 13 rnd)  for the USP compact 9mm.  Correct?  So, the magazine should be the same for both?  The difference between the 10 rnd and the 13 rnd would be one  or a combination of the following components:  follower, spring or the floor plate?  Does anyone know for certain?  Thank you.  

The 10 rounder and the 13 rounders are completely different.  The baseplates are different, the way the plates attach to the mag is different, the mag bodies themselves are different.  No way I can figure to make a 10 rounder into a 13 rounder.