I've noticed the same thing with my 2 PF9s. Only problems I ever had was after shooting a lot and since I've limited myself to about 50 rds per sesson, no problems. I shoot one or both first, then move on to primary carry pistols.
Took the PF-9 out again this morning with 100 rounds of WWB 115 grain FMJ and seven rounds of Federal 124 JHP (hydra-shok). The Federals ran just fine. The WWB box went through the first twelve magazines without a hitch. Thirteenth magazine load had a stovepipe, most likely caused by limp wristing since I was trying out point shooting from the hip (I know, not recommended practice). The fourteenth magazine load had a nose dive caused by my failure to fully seat the magazine. I think I was getting tired by the last two magazine loads and overlooked some basic rules with regards to proper grip and bumping the magazine home.
I haven't changed my mind about making this my primary concealed carry piece. However, I think I'll restrict myself to fifty rounds per session to avoid developing bad habits - easy to do since this pistol is so light extend shooting sessions get unpleasant. My overall impressions remain unchanged and I'm happy with my newest acquisition.
I've noticed the same thing with my 2 PF9s. Only problems I ever had was after shooting a lot and since I've limited myself to about 50 rds per sesson, no problems. I shoot one or both first, then move on to primary carry pistols.