.300 Blackout Chamber Problem

[Rucker61]

I've got two sets of .223 formed .300 Blackout brass, about 400 pieces from Hoser and 500 pieces from an online source. Brass is sized, and within specs for case length and neck size. Empty case fits in Lyman case length gauge, as do the loaded rounds (110 VMAX, 2.05" COAL). The loaded rounds chamber but won't eject, and have to be banged out. Factory Hornady ammo fits in the gauge and ejects easily. Factory ammo is on left. Any ideas?


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[Jamnanc]

Bolt or ar platform? Subsonic?

[Rucker61]

Bolt or ar platform? Subsonic?

Sorry. Two different AR pistols, supersonic (110 grain).

[Jamnanc]

I’d guess overpressure. I bet Hoser or another guru can tell you for sure though. Are you running an expander ball? Looks like there might be some neck expansion. Maybe too much crimp when seating making that area swell.

[DireWolf]

Sorry. Two different AR pistols, supersonic (110 grain).Are the barrels from the same manufacturer?

Just a guess, but wondering if possible that chambers may be cut just a bit too tight and might need to undersize brass just a little...

I've had 300BO barrels that failed to close on a GO gauge (with multiple bolts), but would lock completely closed with factory ammo and shot fine.

Just a thought...

[Rucker61]

Are the barrels from the same manufacturer?

Just a guess, but wondering if possible that chambers may be cut just a bit too tight and might need to undersize brass just a little...

I've had 300BO barrels that failed to close on a GO gauge (with multiple bolts), but would lock completely closed with factory ammo and shot fine.

Just a thought...

One is a Radical Firearms upper, the other is a Ballistics Advantage barrel.

[Rucker61]

I’d guess overpressure. I bet Hoser or another guru can tell you for sure though. Are you running an expander ball? Looks like there might be some neck expansion. Maybe too much crimp when seating making that area swell.

I sized the ones from Hoser (twice!) and the others were sized by the "manufacturer".

[sellersm]

Get a Sheridan Engineering 'slot' gauge that shows what's going on: http://www.sheridanengineering.com/index-2.htm

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[Rucker61]

Get a Sheridan Engineering 'slot' gauge that shows what's going on: http://www.sheridanengineering.com/index-2.htm

76637

Interesting.

[Tim K]

You can't get a loaded round to eject, right? Sure the bullet is not in the rifling?

Try bumping the shoulder back another 0.005". My money is on that being the problem.

[20X11]

Also, certain headstamps don't play well for "converted" 556 brass...necks end up too thick. 300blktalk.com has more details on this...search for headstamps

[izzy]

I have one of those slot gauges and it helps a lot. I've loaded and shot almost 1000 rounds from brass converted by hoser, I'd say maybe 1 out of 300 just never fit into the gauge, I toss those and move on. With a wide array of different headstamps I haven't noticed a pattern there.

[Hoser]

Some chambers are a bit snug with certain flavors of brass. Most US headstamp brass works fine, but an occasional cat and dog will mess things up.

Measure the neck OD of a loaded round and compare it to a few empties fired out of this gun. That will tell you.

[bobbyfairbanks]

I think Tim is on to something!