Case Head Separation in .223

[David Sinko]

My brother had a hard time getting bulk .223 loaded ammo for his department and had to get Black Hills remanufactured. He took this ammo and a Mini 14 to a class and experienced three instances of case head separation out of 700 or so rounds fired. Does anybody have any idea how many times this brass might've been loaded before Black Hills got a hold of it? Are there any other factors that could cause this? Any Mini 14 issues? How many times can .223 be reloaded before you can expect to see this happen?

I'm concerned because he gave me much of the fired brass and I am processing it for my own use. While processing it I have found two cases that are on the verge of being cut in half and the impending separation line is cearly visible on the outside of these cases. They look so bad that I'm afraid they'd separate in the sizing die if I tried. These two offending cases are both WCC but he's sure the ones that separated in the Mini 14 were Lake City.

Dave Sinko

[Dan Sierpina]

To my knowledge, Black Hills always used once fired brass. My first thought would be that the chambers in the Mini 14 was on the large side. I would try it in another rifle.

[HoMiE]

I have had 2 case failures with BHA once-fired ammunition (68 gr. hpbt blue box). Shooting the rounds in a rem 700p in .223, the first one was case head seperation (bout 2/3 around, didn't completely seperate so case came out). The second failure was the neck split length-wise to the shoulder. After that, I quit buying and using the blue box stuff. I only buy the new brass in the red boxes now.

[wsimpso1]

Case head separations are caused by the case body just forward of the case head being stretched beyond the material's capability. This can happen on new or once fired cases with excess headspace or on cases that have been loaded quite a few times. This is why when we handload, those of us that want to get a lot of loadings from their cases do several things.

Keep each batch of brass together;

Adjust your sizer to give no more than 0.002" headspace;

Check brass for evidence of incipient head seperations;

Deep six the whole batch when you can detect thinning.

In your case, I would bet that headspace in the gun is excessive. Here's what happens when either the chamber headspace is large or the ammo is has a short headspace length. The cartridge fits between the bolt face and the chamber shoulder. Whenthe firing pin strikes the primer, it shoves the case forward until the shoulder of the case sets against the shoulder of the chamber, leaving all of the excess space between the case head and the bolt face. The primer and then propellant fires, the case, starting at the neck, expands to the chamber wall, and then the chamber plus case carry the pressure from the powder. As you go back towards the case head, the wall gets thick enough that it does not expand out to the chamber. As the pressure continues to grow, the case head is shoved back against the bolt and the case wall at the back of the case stretches. This is how after firing, the shoulder is farther forward than it was before.

Sizing does not fix this, it just shoves the shoulder back. So, the smart handloader will make a probe and feel for the inside of the case near the head thinning down. And deep six the whole batch when it does.

Billski

[Carlos]

In your case, I would bet that headspace in the gun is excessive.

Billski

-agree. Separations with blue-box are probably also due, in part, to some of the brass having been fired through 5.56mm squad automatic rifles (M249?) which is apparently very rough on brass and stretches it excessively on the first firing.