Primers backing out .30 Carbine

[Twinson]

What would cause the primers to back out after firing? These are sticking out about 1/16". Not all of them stuck out but is seemed like the first 5 or so did and then it seemed ok and then only once in a while one would stick out.

Gun: USGI M1 Carbine
Bullet: Hornady 110gn round nose
powder: H110 @ 13.5 grains
primer: WSR
brass: LC 79
trim length: 1.284

Information

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[USSR]

Primers backing out are typically a sign of low pressure. I'd try bumping up your powder charge 0.5gr and see if it goes away.

Don

[MEHavey]

Pressure's probably too low (QL ~26,000psi) to slam/stretch the case back to reseat the primer after it initially backs out upon ignition by the amount of available headspace. You'll see the same thing if you fire an unloaded-but-primed case.

QL suggests 110RN/15.0gr H110 for right at 2,000fps -- military loadout

Hodgdon Data says:
H110 14.0gr 2,006 32,000 CUP
H110 15.0gr 2,106 36,500 CUP

See http://data.hodgdon

[jimb16]

You probably see a lot of soot on the case as well. That is another sign of low pressure. Bump it up half a grain.

[Larry Gibson]

Not sure what length barrel Hodgdon uses in it's testing, probably a SAAMI test barrel, since they give pressures, longer than a M1 Carbine barrel. In numerous M1 Carbines 15 gr H110 under a 110 gr Hornady RN gives 1920-1930 fps. That is a pretty close duplication of the 107/110 gr US military ball load.

Larry Gibson

[Sunray]

"...typically a sign of low pressure..." And excessive pressure and bad headspace. Neither of which is likely. Unless you've changed the bolt without using headspace guages.
13.5 grains of H110 is .5 of a grain below minimum. Hodgdon gives 14.0 to 15.0 for a 110 grain jacketed bullet. That half grain shouldn't cause primers to back out. Try loading some commercial brass with 14.0. You should work up the load though.