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Old 09-04-2021, 09:51 AM
2152hq 2152hq is offline
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When the case expands and bulges excessively down at the head and then you push it back into orig shape in a die,,the brass is probably already work hardened beyond where it should be.

The case head portion of a cartridge is supposed to be harder (temper) than the mouth to contain the pressure of unsupported brass in that area.
But some guns have more unsupported area than others.
Some brass starts out a bit softer than it should in that area.

When you bulge it that far that's cold working the metal. It might already have micro cracks in it.
Then the sizer die pushes it back into shape and all looks well, but it may crack more or that second operation develops cracks and more brass hardness.

Then when it's fired and that area is unsupported once again there's a good chance it may not bulge and hold,,but just blow out.

I was shown a STAR Model B-Super not long ago that a case blew out. That in turn cracked the plastic grips and blew some brass into the shooters palm of his grip hand.

The problem was that the feed ramp of the gun, both the frame & bbl,,had been altered slightly in attempts to get hollow pt and other bullets to feed better. That left the case unsupported much more than the orig design which had a rather steep and abrupt ramp.

But the pistol was designed to used FMJ ammo and they work just fine with that in most instances.
The ammo was reloads as well,,so they may have also been bulged from previous multiple firing & reloadings and the brass suffered from the above condition.

My best advise was to use factory FMJ in the STAR. Or if he want to continue to reload,,use other new or once fired brass (that shows no bulge on the case).,,reload that and then toss it.
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