[Sevens]

I have a couple theories, and I hope if nothing else that you get a thread bump and someone else gets involved. Better yet, if this thread were moved to either the gunsmithing or the reloading forum, it might get seen by folks who have the correct answer.

One theory has to do with the timing of the pistol -- if the lockup is ill-timed and the slide moves rearward too quickly, there won't be a breech face that is covering the primer and the pressure from inside will attempt to take the path of least resistance. Given that you just put the pistol together, I think this is possible.

But not being a gunsmith, I have no idea if that is a valid theory, but I'll throw it out there since you haven't had much luck with other posts. (yet?)

The other easy theory is that yes, these loads are too hot and you are seeing a sign of high pressure. I'd like to know the bullet, weight, powder and charge, and COAL, that might help.

Last theory is the one I'm most sure of -- it may or may not be causing your grief, but I'm for DAMN sure of it:

A-Merc brass is the worst brass on the face of the earth.
It's awful. There is no brass made by anyone that is nearly as bad. Sure, there are some berdan primed or aluminum brass that isn't even reloadable. Yes, those are better than A-Merc, because at least with them, nobody gets conned in to actually trying to reload it.

A-Merc brass is one of those things in the world that I crusade against. (for the curious, TicketMaster is another)

I don't have the energy to detail every reason I hate the stuff, but if you run the search engine, you should find some of my posts complaining about it. Hopefully, you'll find others as well.

In my opinion, and I stand by it, neither you nor anybody else should ever, under any circumstances, reload A-Merc brass. It's fodder for the recycle bin. There's nothing good about it. And do the entire shooting fraternity a big favor, and weed it out of ANY brass that you have and recycle it before it gets dropped, traded, or otherwise forwarded to any new reloaders who don't realize how awful it is.

The job the brass has to do is way too important, to your firearms and to your hands and face to be left to THE worst brass on planet Earth.