What causes this?

Were these found cases that you took home and resized with a carbide die? I'm always suspicious of found brass - particularly found magnum brass.

I've seen this before. The cartridge has been fired in an oversized chamber and the carbide ring in the sizing die overworks the brass and swages up a tiny ridge of brass as the case is pressed into the die. The little ring can sometimes be prevented by lubricating the oversized brass with a tiny amount of sizing wax - allowing the carbide ring to slide freely over the brass without raising the ring. Some folks routinely lube brass meant for carbide dies anyway. I don't do this, but a squirt of Hornady One-Shot into a baggie full of brass usually does the trick.

I had a Ruger .45 Colt with an oversized chamber that "ruined" all of my good brass like this. I have continued to shoot those cases with the little swaged ring many more times - for many more years in my Colts - with no problems. Eventually, some of those cases split longitudinally from old age - but I've never had a head separation. However, I make it a practice to load the hot stuff only in new or known first-class once-fired brass.

BTW, a head separation occurs from the inside-out. You first notice it a a faint lightly-colored ring near the base - indicating stretched brass over a thinning area inside the case. A head separation won't show a raised ring on the outside. Here are a couple of near-separations on some old well-used .30-40 cases. Note how the rings swage inward into the cases - rather than raise up on the outside.


xtm

Let me clarify something....

The raised ring caused by the carbide ring wouldn't really bother me if the case was from a known source and I knew exactly what caused it - but the little radial nick just above the raised ring would give me cause to wonder about an incipient head separation. I might be compelled to take a hacksaw and see for sure.

When in doubt - throw it out!

Head separations are a real PITA because they usually leave a piece of stuck case in the chamber and you have to figure out how to get it out without scratching up the bore and chamber. Modern firearms have gas vents or other means that direct gases away from your face, but some antique guns do not have this safety feature. Best be prepared and wear safety glasses anytime you shoot! If you shoot frequently enough, you're probably gonna have one or see one - they occasionally even happen with new factory rounds - particularly with foreign military stuff, so you need to be prepared. I once had a .303 Enfield that would have one nearly every time you pulled the trigger! I was with a friend when he had a head separation while shooting factory ammo in his Savage 99 chambered in .30-30. This was in the years before everyone sued for anything.... we concluded that the factory brass had not been properly annealed, and his chamber had slightly oversize headspace. No harm to him, but the gas was vented back into the head of the buttstock and split the wood. He's shot the rifle 100s of times before and after that incident with no problem - just with that one box of ammo.

xtm

It took me a while to find these!

Here is a box of prepared, ready-to-load .45 Colt brass. Inside, some have the same swaged ring near the base - and some don't. All were sized and otherwise prepared in my old set of Pacific reloading dies. It's apparent to see which cases were fired in my Ruger Blackhawk with the oversized chamber and swaged back to spec. by the carbide ring.


I dug around in my ammo bin and found this box of .45 Colt reloads. Each and every cartridge in this box has the telltale ring swaged up near the base. I keep most of my revolver brass segregated by headstamp, lot, and same # of times fired. By the ring, it's easy to assume that I fired all of these cases in that Ruger at some point. I owned that Ruger in the late 1970s, so I can't tell you exactly how many times this brass has been reloaded since then - but it's up in the dozens of times. None have ever separated at the head, but some have split lengthwise from old age.

Looks similar to David's case?:


xtm

I keep going back to David's question..."What causes this?"

He didn't ask, "What should I do with this case?" :lol:
I think we all agree that due to the unknown history of the brass, it needs to be recycled.

I'm 99.9% certain that the radial ridge was swaged into the cases by a carbide ring on a sizing die. It's too close to the base for me to believe that it is the beginnings of a head separation. That would likely occur some distance above that ring - where the case brass is much thinner and prone to stretch even thinner. That is why the little radial nick above the ring bothers me a whole lot more. It is located just about where I would expect a head separation to occur.


BTW, Boats,
I've quit compressing BP loads in my single shot cartridges - and I quit necksizing the cases. I have convinced myself that one or both of those two things significantly reduces the life of my brass. I'm leaning toward believing that the necksizing is the worst of the two culprits and now shoot them strictly fireformed to the chamber. Unfortunately, much of the BPCR advice I'm reading nowadays is parroted from one "expert" to the next and reeks like a steaming load of BS. A lot of 'em need to re-read the older literature and get back to the basics.

xtm