I have a Panther arms upper, 24" bbl, 1-8" twist, no fwd assist. I got several FTF's today, while using a new load. The load is 80gr SMK in commercial Black Hills cases, using WW primers. Bullet is seated to C.O.A.L. of 2.55" per Sierra loading manual.

Since the rounds won't fit into mags, I single-loaded laying round on top of Colt 10-round mag.

Using bolt release, the round chambered, but then would not fire. I pulled the bolt, disassembled and checked for any damage, but found none.

When I attempted to eject the unfired round, I noticed the round stuck, and only with difficulty would the case eject manually. The bullet itself was stuck in the throat, and the bullet separated from the case. I had to use a cleaning rod to remove the bullet from the chamber. After the second, identical failure, I stopped the ammunition test.

I put the original Olympic Arms upper back on, and it functioned perfectly with standard commercial .223 ammunition, so I believe the lower doesn't cause the problem.

From observation, it appears that 2.55" C.O.A.L. is too long, and bullets should be seated deeper in the case.

Is it possible that the cartridge's too long length kept the bolt from fully engaging, even afte forcing the bullet into the barrel lands?

Any help is greatly appreciated.
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