What is this caused by?

[ziconceo]

I've never had this happen before. This is the brass case fired from a m91/30 Mosin nagant. The specs for the round were:

PPU, 150grain sp factory non reloaded. Out of the 80 PPU rounds I shot, only one did this. Anyone got an answer for me? Thanks!

[asm_]

Did you step on it?

[ziconceo]

Did you step on it?

Lol no. I always shoot with an open box next to me so all of my brass just lands in there and I don't have to pick it up.

[hemiguy55]

That should buff right out!

[the86d]

Either magic, or you might have picked up a stepped-on case.

I have picked up some 5.56 brass from the range that had been stepped-on and was similar. I reloaded it, and fired it as a test and could not tell which one it was from the other fired brass after a tumble...

Oh, and:

That should buff right out!

Indeed.

[6mmintl]

If it was there before firing its a hydraulic pressure mark during case forming.

If it was after firing it was caused by low pressure/power cartridge allowing gas to bypass unexpanded neck into cartridge base/body.

[mark501w]

Light load.

[knucklehead0202]

if the load were too light it'd probably be dirtier. was anyone nearby you shooting an autoloader like an svt-40 or psl/dragunov? both of those beat up brass pretty bad. I picked some up from the range last time from a guy that was shooting both of those rifles and some cases were pretty dented up. never seen anything like that come out of a bolt gun that didn't blow up.

[ziconceo]

if the load were too light it'd probably be dirtier. was anyone nearby you shooting an autoloader like an svt-40 or psl/dragunov? both of those beat up brass pretty bad. I picked some up from the range last time from a guy that was shooting both of those rifles and some cases were pretty dented up. never seen anything like that come out of a bolt gun that didn't blow up.

Exactly, I never cleaned the round. And no, I was shooting by myself.

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[CK_32]

Probably hit something at an awkward angle. If it was a few you could have a problem but one case could me any number of things it just happened to do that one time. Possibilities are endless.

[ziconceo]

Probably hit something at an awkward angle. If it was a few you could have a problem but one case could me any number of things it just happened to do that one time. Possibilities are endless.

I see, Sooooo...the question remains...can I fire it?

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[mark501w]

tumor in chamber? you can reload it.

[knucklehead0202]

I'd reload it, a little light just because of slight diminished capacity and fire it, it'll probably fireform alright.

[BruinGuy]

I've reloaded brass with far worse dents than that! Most of the dent will come out when you size it...the rest will come out when you shoot it.

[knucklehead0202]

BINGO!