Longitudinal case rupture

[triggerjerk]

Young man at range today with relatively new ar complaining about dirty, gas to face and split cases. Allegedly old (Dad's), factory 50gr hpbt Federal. Split runs lengthwise from rim (yes, into primer pocket) forward a half inch up the case, not around the case forward of the web. It appears the web was cracked, also. Said he'd shot 400 of em and a few other different bullets no problems. But this box (allegedly 200 per box) was splitting cases as described.

Has anyone seen this, and what would the mechanism of failure be? Silver primers leaves me suspicious of them being reloads....

[georgeib]

Chamber could be reamed too loose, short headspace, batch of poorly heat treated cases, or a couple other possibilities including overworked cases.

[JimmyB62]

Under relatively rare conditions powder can go bad and severely corrode the brass from the inside. I can’t tell you what the exact chemical process is. The outside case may look fine but the inside is corroded and substantially weakened. This may be the cause but it should also be readily apparent if this occcured by looking inside the fired case.

The Federal .223 200 rnd value pack was a popular item some years ago and had a 50gr HPBT bullet with silver colored (nickel plated) primers cups.

[markm]

Under relatively rare conditions powder can go bad and severely corrode the brass from the inside.

My vote is for this. I've seen something similar where a guy I know had ammo stored in a house with a swamp cooler. The brass deteriorated to the point where necks were splitting and all kinds of crap.

[anachronism]

My vote is for this. I've seen something similar where a guy I know had ammo stored in a house with a swamp cooler. The brass deteriorated to the point where necks were splitting and all kinds of crap.

I think I'd pull a few rounds down and inspect them internally.

[markm]

I think I'd pull a few rounds down and inspect them internally.

Me too.

[mack7.62]

I had case failures like this from some condemned IMI 7.62x51 that was sold as surplus instead of being destroyed. Theory was that the cardboard used to make the 20 round ammo boxes was not acid free and caused the brass to become brittle.

[triggerjerk]

I have one of the cases. Deprimed it (had to put on top of shell holder cause split rim wouldn't begin to go in shell holder. Web is split from outside of case to/including wall of primer pocket but not into bottom of pocket itself. Inside of case isn't obviously corroded, but that doesn't mean it isn't corroded. Flashlight/magnifying glass not very efficient. One might assume all 600 from same lot/storage conditions, but who knows. Maybe he just didn't notice splits from the 400 "that shot fine". Advised him to quit shooting it. He only had 2 30 rounders full remaining.....

[markm]

I'd just blast the stuff. The brass is just not reloadable... or shouldn't be anyway.

[triggerjerk]

Last 60 rounds prolly wudda been ok. Have read of alleged boltface etching from primer leakage. I figured err on the side of caution for chamber etching or other unforseen failure. Again, it wasn't just a split neck. It was a full half inch or better from the base forward and included part of the web......