I ran some Grizzly Cartridge rounds through a new 500 S&W yesterday, and had a hard time extracting the spent casings - to the point that I had to drive some out of the cylinder with a punch. I cleaned up the casings so I could get a good look at them, and IMO there is some significant pressures going on.

All rounds show the "ring" near the head, and almost all have cratered primers. Only one casing has a chewed up mouth though, and I can't imagine what caused this. Any ideas?

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Too many S&W's to mention...

The primer shows evidence of metal extruding back into the firing pin hole in the breech face. That can be caused by either high pressure, an oversize FP hole, or a weak FP spring. No idea what caused that chewed up case mouth.

The cratered primer in the photo look like a low pressure load in some rifles I have with funky chambers, the edge line is still pretty round! I have extra hot 44 Mag loads that the only way to tell where the primer ends and te case rim begins is the color change.

I would scrub the chambers super clean and dry and try your test again.

Ivan

That's from your punch.

The punch was used on the head.

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Too many S&W's to mention...

Thanks. The gun is super clean, I'll be loading up some 500gr jacketed rounds once the brass shows up so we'll find out. I don't think I pointed out the impression on the head from the milling mark on the breech. I'd think it would take some serious pressure to cause that imprint.

I plan on dissecting a few tomorrow to see what the case wall looks like near the head.

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Too many S&W's to mention...

Run some factory rounds and if they stick you have a problem with the cylinder and would be easier. It looks like primer flow for some reason. I would like to know the outcome.

Somebody sure as heck did something, knowingly or not, to distort and disfigure the mouth after that round was fired. Pressure blows brass to conform perfectly against every nanometer of the symmetric wall in the charge hole. The brass mouth is now asymmetric and carbon-free on a few flat spots. Think your cyl wall was responsible for that? That would be a major problem and concern for danger. Inspect your cyl walls - you'll likely find scratches from your punch.

Grizzly is known for full loads but you case seems a little over board.

Your weapon might have a defect...............
I would talk to the ammo and gun maker to see what they say.

I for one would not want something to go wrong with a BIG 500 in my hands !!

I had a S&W that was shaving copper and drawing blood on my face.........
the company fixed it , no charge and all is good again.

Good luck and stay safe.