Damaged brass, stuck bolt

[double0b]

Hi everyone.

Today was the day to test my first hand loads. Was a bit apprehensive at first, but the first fired as expected. All was going great until round #19. Below are some pictures. None of the other brass had any damage or looked otherwise abnormal.

Firearm - AR-15 White Oak service rifle upper
Brass - Lake City trimmed to 1.750
Bullet - 77gr Sierra Matchking HPBT
Power - 24.1gr Varget
Primer - CCI 400
OAL - 2.260

When the malfunction occurred, the bolt cycled properly, chambered the round fully, fired, jammed. It appeared that the bolt teeth began to disengage - moved to the rear about 1/8-1/4". I could not cycle the bolt using the charging handle, nor could I move the bolt using the forward assist. I ended up using a leather mallet to free the bolt. The primer fell out along with the brass. The case head appears ovalized and the base is swollen a bit.

Any ideas on the cause, places to begin investigating?

Thanks!

[double0b]

The measured length of this brass is now 1.740. Do you think this is an over pressure issue? A OAB with a safe ending? If OAB, I would expect some damage to the neck.

It was sized with a Lee full length die. Case is once fired military brass.

I'm taking the rifle to my gunsmith tomorrow to have it checked out.

[ww2m38]

...............

[double0b]

I guess that would have been some good information to list from the beginning.

bullet - 77gr Sierra Matchking HPBT

I'm using a Dillon 550B. The powder throws were calibrated using a Franklin electronic scale.

I've seen that link that you provided, ww2m38.

If I place the brass in question in my Wilson case gage, the expanded/swollen part fits squarly, as if the case wasnt fully chambered when it stretched.

[6079Winston]

That's either way over pressure or that case head was really soft. Was the brass once fired by you or somebody else? Improper annealing might soften the brass too much at the case head. Charges weighed individually or thrown? I'm not sure if you can get enough Varget into a .223 case to cause this, but too little might be a problem. A ball powder might be a better choice for the Dillon powder throw. In any case you should hold off on any further reloading or shooting until you get a professional opinion on this. I would suggest sending White Oak an e-mail with details and pictures.

[rksimple]

Where did you get the brass and how many times has it been fired? With as much ejector flow as you have, there was definitly a pressure issue. Are you crimping? Did you see where the round impacted in comparison to the rest? Could've had a setback causing a pressure spike...maybe.

[mif_slim]

That primers flat. Over pressure some how. And is that a ring I see on the base? I've never seen rings on .223 before. If it didnt have rings before, its over pressure for sure. The bent rim also shows that its over pressure. The extractor had to work extra hard to pull out the brass from expanding to much.

Maybe the the bullet sat back as it went into the chamber causing higher pressure?

[bohoki]

to me that seems like a bit of a hotload for 77 grain try 22 grains it still gets there just a tad slower

[ocabj]

24.0gr Varget and a 77 is a medium load. I use 24.0gr RL15 and that's about as equivalent as it gets without actually using Varget.

[Bedlam]

He would be withing allowable charges even if he was loading an 80 gr bullet.

[double0b]

My gunsmith checked out the rifle and the remaining loaded ammunition, along with the case in question. It is his opinion that the round went off OAB. He also advised to trim to 1.745 to give a bit more clearance. Left my upper with him to inspect the chamber.

[rksimple]

That really does not look like an out of battery firing. And trimming is not the source of your problem.

[double0b]

Here is a thread with pictures of a very similar situation. The poster states that his ammunition was a factory load. While I completely can see that pressure was a factor in my case, there was definitely something else going on there.

http://www.akfiles.com/forums/showpost.php?p=342442&postcount=32

[Rob454]

My Savage does that. I shoot a round then its a PITA to open the bolt to eject the round. It only did that when i shot some old 30-06 I found in the garage. it was some mil spec stuff. I usually shoot hunting asmmo and its when I sight it in for when i get ready to go hunting. The US brand ammo I have no problems with. its when i shoot some cheapo ammo it gets funky.