I was shooting PMC bronze90 gr fmj ammo, 2 boxes, bought at 2 differant placed near Denver Colorado, this is dirty ammo, i shoot it in a differant caliber in my Glocks all day long never a problem....i took the gun apart cleaned the firing pin and the inn er slide hole out, and will try again tomorrow to shoot it....I have owned several keltec pistols, never a problem, except with a p40 years ago...kel tec sent it back with all new parts except the outer frame.....
If it is gun related, the hammer has to be the problem.
You could look at hammer with slide off to see if there is something catching before it goes past straight up. I would use thumb to control hammer travel and feel for any hesitation that would hang up the travel then let go. If the hammer block is catching (that position is hammer straight up, there should not be enough impact to fire if hammer fell from block
check the hammer notch in the slide for a machining step that could catch the hammer
I found an unusual hammer problem, where the hammer would catch during travel and not strick the firing pin.
I have uploaded a 20 second video of the problems I am having. ..if we pull the trigger slowly, the hammer block pops back into place before the hammer can reach the firing pin. If we pull it quickly, it works fine....http://www.youtube.com/watch?v=Gx_dxE3dbv0
I am not a fan of the PMC ammo. I found it to be very dirty and did have one FTF at the range. Probably not a great idea, but after waiting a while (pointed downrange) I ejected the shell and reloaded it in the mag and it fired the second attempt several minutes laters. Brand new P3AT.
Conversely with Sellier and Bellot ammo I have had zero issues and it is a much cleaner round. Based upon my experience, I'm staying away from PMC.