(This turned into a lengthy post, so I have highlighted the most important points in red) Hello all. I'm having quite the headache and I hope some here will be able to help troubleshoot. First, a bit of history on the gun in question: it's a Poly80 PF940C with a stock lower parts kit and a complete Rock Slide Auto G19 Gen 3 slide with glock parts pre installed. The gun required an unusually long break in; the first mag or two ran OK, but until it miraculously started running flawlessly at around 600 rounds, it would Fail to Feed (round would be half out of mag jammed against the feed ramp) nearly as often as it went bang, occasionally failing to eject as well. Not a limp wristing issue, mind you, and after enough rounds the gun had become perfectly reliable. The rounds in question were 9mm Fiocci 115 grain FMJ. They ran great, even with an Ebay muzzle brake (we found one that matches the shape of the RSU slide exactly)! For a while I have been fascinated by 22 TCM/22 TCM9r as an alternative to defensive 9mm loads. Before prices went insane over the summer, 22 TCM9r was around 30c a shot, or about double the price of target 9mm. However, defensive 9mm tends to run over a dollar a round, which of course discourages people from training with full power loads as they ought to. So for 1/3 of the price of defensive 9mm, you can get arguably better performance, with less recoil, plus training rounds and defensive rounds that are the same. Seemed pretty attractive. Once even the cheapest (quality wise) 9mm started creeping up past 50-60c each, 22 TCM9r seemed like a no brainer at 33c/round. The barrel/recoil spring conversion for gen 3 G19 runs well under $150 on eBay, so I figured, "why not?" If you're thinking by now, "okay, this is some guy from Armscor who's come to shill their exotic new whiz-bang caliber," don't you worry: what I'm going to tell you next will quell that suspicion! Now that the background is out of the way, here is the tale of the headache (sorry to build suspense, but I want to provide as much info as I can before I start asking for help). If you want to get right to the point, start here: After finally installing the new barrel and recoil spring, three test shots were fired and the gun cycled flawlessly. The potential fourth round was manually removed from the chamber. The giant fireballs this load produces are very exciting, so Billy across the street was called over to give it a try. He managed to fire one round, and got a click on the second. The click sounded very weak and dull compared to normal. The primer had a small, but not insignificant dent. After some manipulation of the slide and dry firing, the *click* started to sound correct, so we tried again. BANG, BANG, click. Another light strike. We took out the firing pin assembly and noticed that it had dirt and oil inside (it was over oiled, although it ran through 9mm just fine in this condition). It was disassembled and wiped down along with everything else (full upper detail strip minus channel sleeve) and reassembled to try again. BANG, click. Light strike. Rack and dryfire, reload and try again. BANG, *chnk*. Light strike. The click of the firing pin had gotten worse! Cock it again, *chnk*. Light strike. By now we started hunting for the shells that had fired and ejected to inspect them. The one shell casing we found had a hole in the primer! Not only a hole, but a fairly large, rectangular hole, similar in size and shape to the hole the firing sticks out of when it strikes the primer. Eventually we found one of the shells from the initial test fire, and it did not have a broken primer. By this point of the story, we were operating under the assumption that user error contributed to the malfunction. It's true that the inner workings of the slide were contaminated with oil due to over oiling, and this is known to cause issues. We decided to take the gun apart and more thoroughly clean out any oil with q tips. Reassembled once more, the gun was test fired once and malfunctioned with a light strike on the second shot. Racked again, met with a very dull *chnk*. No shell was recovered (but I now suspect the one that fired had a hole in the primer). Once more the slide was disassembled, and this time something new happened: the firing pin channel sleeve came out with the firing pin. It particularly, and to a lesser degree the other firing pin assembly components, smelled strongly of spent 22TCM9r. The shot cups were pressing against the firing pin channel sleeve, with enough friction to prevent the firing pin channel sleeve from meaning seated upon removal of the firing pin assembly. It was then that it dawned on us that if there is a hole in the primer, then certainly hot gas would vent into the firing pin channel. This was further confirmed when one of the firing pin spring cups snapped off 30% of its mass upon further disassembly. The half broken spring cup got completely lost when reassembly was attempted. Originally, we thought that user error, or a complication with the spring and barrel swap, was the cause of the troubles. But why would a barrel and recoil spring swap cause gaping holes to be punched in the primers? Could over oiling cause these symptoms? It seems unlikely. The gun ran fine on 115 grain 9mm FMJ. After having written it all down, the conclusion that leaps out at me is that the ammo is at fault (Armscor 22TCM9r, they only make one kind). Surely it stands to reason that if the same over-oiled firing pin never busted out 9mm primers, then it's the fault of the 22TCM9r ammo that its primers are being destroyed? Should we reach out to armscor? Assuming the ammo is manufactured correctly (or not), the preferred route is to get the gun running it properly. It seems to be that in its current configuration, the gun is semi-reliably blowing holes in the back of the primers, which causes hot gas to damage/foul up the firing pin channel sleeve and firing pin assembly. This did not occur when using 9mm. Would it be correct to assume that the only two possible remedies would be to either file down a spare firing pin until it stops blowing out primers, or experiment with lighter striker springs? Which would you recommend, or would you recommend reaching out to armscor, or another option? Thanks to all in advance who read and respond.