IAW post 48: We proceeded to fire only a couple of mags through it and checked the potential crack when we got home. We did this 4x with no increase in the line. We then upped it to 76, then 126, then 200... no increase or change. Yesterday we put 276 rounds on it in one session (including 5 round rapid mag dumps) ... no problem nor increase.
Further, I checked back in our photo records. I keep extensive photo journals of all range pistols and parts. In the folder of the total disassembly for detailed cleaning @11,400 rounds I saw that the line was already there. That means that the line or crack was there for 3,482 rounds before we noticed it. The picture shows the line to be the same then as it still is @15,665 now.
We plan to continue shooting it 200-300 rounds per session, once or twice per week. We will check it afterwards every time. So far it seems that the pistol will not be stopped by this line. It is a thick piece of metal and a thin line that is not increasing (as far as we can discern).
Another PX4 not stopped by part mishap!