Case head separation

[RVTECH]

Would it be reasonable to assume case head separations on RIMMED cases would be much more unlikely than rimless cases?

A couple years ago Out shooting my Henry BB .357 and I fired, cycled it, and noticed only the head and about 1/4" of the case ejected. I had to reach in with a pick and pull the rest of the case out.

Long story short but several of the rounds did this. FWIW It was Sellier & Bellot brass.

I picked up the intact cases and slid a dental pick down them and discovered several of them had a cylindrical 'ring' indentation near the head of the case. The outside of the cases looked normal.

In my life of loading who knows how many 1000s of rounds of .357 I had never had this happen before (and never rimless) , and for the life of me cannot even guess as to what cased the 'ring' indentation on the inside of the cases.

My thought being because It head spaces on the rim, is in the chamber as far as it can go, and is held in place by the bolt face so it cannot move rearward upon firing which I always thought was the cause of case stretching and ultimately separation.

I was discussing this on another forum and one member was adamant it did not matter rimmed or rimless case stretching can occur.

Fire away!

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[oremike]

Any brass in time will wear out, I have seen more case head separations on rifle cases as compared to straight wall pistol.

 

[RVTECH]

I have seen more case head separations on rifle cases as compared to straight wall pistol.

And this is what I have been reading about as well, IE it happens MORE with rimless rifle than straight walled RIMMED - but still can.

Oh well, I guess it was just finally my time to experience it.

FWIW the brass I was using was range pickup, and appeared to be once fired, as it did not have a 'aged' appearance to it but I'll never know for sure.

 

[Spitpatch]

With some measure of experience shooting rimmed AND rimless highpower smokeless rifle cartridges, as well as rimmed and rimless handgun cartridges, it is my observation that head expansion and case stretching (both causes of head separation) can occur in ANY style case, and in equal frequency given equal (harsh and/or repeated) treatment of that brass.

If there seems to be an observed difference in frequency of such when comparing straight-walled rimmed pistol cases as opposed to rimless highpower rifle cases, such difference may easily be caused by the general higher-pressure loadings and tendency to "push the envelope" more with rifles.

Run your .357 against the wall over and over again, then run your .30-06 against the wall over and over again, and the case failure rate in my estimation would be about equal (assuming no headspace/mechanical defects exist in the guns).

Crappy, cheap brass (ESPECIALLY when taxed repeatedly) takes all bets off the table, and can destroy a gun (almost did with me, along with an eyeball protected by God-sent shooting glasses picked up from the optometrist just the day before).

 

[orygun]

That ring is the place where the case stretches when firing. I have one 30-06 case that was sticky on removal from the chamber because it almost split and seemed to "spot weld" itself in place. Using the paper clip trick, I found that case was about to separate.
I tossed all of that batch away.
I can picture it happening more frequently on rimmed or belted cartridges that are fired in an oversized chamber. First being stretched too far, then being resized to proper spec. The brass flows to the front, requiring trimming, but you can't squish the metal bask in place at the rear of the case.

When I was a 45-70 loader, I ran them hot in my Browning. Ruger level hot. Never had a 45-70 case separate and I've never had a revolver cartridge separate. But I've had several split necks on overworked 357 cases.

 

[P7M13]

Glad you're ok.
@tac used to swear on the junkiness of S&B brass.
I shoot easily 20x bottle necked rifle to straight wall anything. I've had split cases on rimmed, straight walled cases, and had case head cracking on bottle-necked, but don't remember any full head separations.
With my straight walled cases, I do a sound check - those that have a nice bell ring to them, or those that have a notably dull sound compared to the rest (crack) are pulled.
I'll check for base bulge next time I'm running straight walled.