Problem With Panther Arms Upper (Posted also on other fora)

[pendennis]

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.

Information

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[browningautorifle]

If your cartridge is too long the bolt won't close properly. If the bullet protrudes too far into the commencement the bullet will stick. The first warning was the rounds didn't fit in the magazine. Check your case length against the book. Check the overall cartridge length in the book. These are published for a reason. If you don't adhere to them there may be dangerous consequences. I would cross reference two or three or more books for measurements to check your work. One different component can change everything. You should probably enlist the help of a friend that has loaded a few thousand rounds successfully and have him look over your shoulder for a while until all is going well. Good luck on this on, I would take that ammo back to the drawing board.

[imarangemaster]

If I remember right, the 80 grain is for bolt guns with special throats. Most will take 77 grain Black Hills Mk262Mod1 because of the ogive.

[pendennis]

The latest on my "woes".

Yesterday, the UPS guy (AKA drugs delivery agent) delivered a nice package from Sinclair. Included was their Sinclair Seating Depth Gauge, AR15 adapter, and some Sierra 77gr MK's.

Today, I sat down at the bench and started the task of measuring bullet seating depths on both AR15 uppers. I've started a chart of the various seating depths, and there are some real differences between bullet/case combinations.

The DPMS upper
For instance, the 80gr SMK, which Sierra says to seat at 2.55" has a total length, touching the lands, of 2.4805". That's obviously the reason for the initial misfires. The 77gr SMK, measured 2.3205"; not very far off from the 69gr SMK, which measured out at 2.3315".

I'll be wading through the Olympic Arms upper next, and it'll be narrowed to 53gr FBHP, 52gr BTHP, and 69gr BTHP. This barrel has a 1-9" twist.

The next purchase seems destined to be a Redding Precision Seating Die, since I can record the various case lengths from its micrometer settings.

Thanks very much for the help.

[gsp2007]

Looks like you alreadya nswered your own question - having the bullet stick in the rifling is a sure sign of them being too long. Bolt will not lock up, preventing full battery and hence, firing.

One respondee said to check the OAL as 2.55 is too long for mag length - that's for sure! The 80's can - and are - fired successfully in AR's (service or match) at the longer range line (600 yards) but as dingle load only. Depending on throat / chamber distances, I would start at 2.45". You probably want to be .010 - .015 off the lands anyway for best accuracy. My newly barrelled service rifle is loaded at 2.45 jsut to be sure, while my spacegun handles 2.50. You can use a Stoney Point or simialr emasuring tool, but 2.45 should be very safe.

Eric