Mid-body case splits can happen with old brass.
They can happen with brass that's been shot a few times.
Or they can happen with brass that's BRAND NEW.
It's normally an indication that there is a weak spot in the brass, either a manufacturing defect or some type of scratch or inclusion.
I've had many of these over the years.
I'd venture to say that the ONLY reason why your friend had brass in his shooting glove is because he was using a light load that didn't fully obturate the case to the chamber, which allowed small pieces of brass and powder gas to escape.
Heavier loads will rarely, if ever, spit brass and gas back when there is a mid body split because the rest of the case, and the case head, expands and seals the chamber.
One of the most impressive case splits I ever had was when firing full-bore .357 Mag. loads -- IIRC 158-gr. bullet and about 19 grains of WW 296.
When I removed the case from the chamber it was split from case mouth to case head, and it actually looked as if a fair portion of the brass around the edges of the split was burned away and sent down range.
Behind the gun, though, I never noticed a thing. The round behaved perfectly normally.
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