Range malfunction Question

So I have two firearms that I took to the range the other day. One of them fires the Federal 115 grain Aluminum FMJ without issue (SIG P938) and the other gun would not fire that same round every few rounds (pt111 g2, over 2000 rounds with no malfunctions prior to this).The first time it malfunctioned with this ammo I would pull the trigger and nothing happened. I pulled the trigger again and nothing happened. I then attempted to pull the slide back to release the round and it would not release. I eventually put some gun lube around the slide to get the slide back and release the round. It has a spot on the back where the firing pin hit it but apparently did not go off. I then changed to using normal Federal 124grain FMJ and had no issues with the same gun until I loaded more of the aluminum cased ammo, and eventually I had a similar issue with two more rounds where the back showed it was struck but it did not go off. I even used some Federal Hallowpoints (124, 135, and 147) and all went through perfectly fine.Is there something I should be concerned about? This was not only a bullet not going off, but also having a difficult time releasing the bullet (pulling slide back) when attempting to clear the gun after the bullet did not go off. via /r/CCW http://ift.tt/2vLg14e