What caused this?

[Freshly Minted Georgian!]

Processing a bucket of 223 I picked up in trades recently I ran across a few shells that wouldn't start to enter the sizing die. I thought maybe they were berdan primed and it was the decapping pin hitting that was stalling things but looking at it I realized they weren't making it that far - they were hitting resistance just as the shoulder hit the die body. Looking closer, the cases are hugely overstretched, like they were fired in a much larger chamber. Maybe a Valk, or a Grendel chamber. I just shook my head, tossed it in the scrap bucket and moved on figuring it was a one time "oops" on someone's part. As I went on though I found maybe a dozen more out of a 5 gallon bucket. Whoever hit the "oops" wasn't exactly a quick learner!

Anyway, for kicks and giggles I did force a couple of these into the sizer but about half way up the resistance was just getting too great and I didn't want to get one stuck so I stopped. Probably could force them by sizing in small increments, being common brass it just isn't worth the risk or the headache. Take a look though, let me know what you think happened here. I ran em through the polisher this morning to make for pretty pictures.

 

[davis211]

25.0 gr of Red Dot will straighten em out!

 

[BHPSteel]

What are the diameters of both of the sections?
Any signs of rifling on the forward section of the case?

A 223 jammed into a 9mm carbine with half the case into the rifled barrel and the back half in the chamber?

223 jammed into a 22-250 chamber?

 

[Freshly Minted Georgian!]

The top half of those has been squeezed back down to close to normal diameter. The lower half is still grossly expanded.

 

[Freshly Minted Georgian!]

25.0 gr of Red Dot will straighten em out!

I’ll load one up for ya if you’ll test it in your 223. Why go as slow as red dot though, I prolly have enough bullseye to fill the case.

 

[davis211]

I’ll load one up for ya if you’ll test it in your 223. Why go as slow as red dot though, I prolly have enough bullseye to fill the case.

I should probably wear safety glasses.

 

[Freshly Minted Georgian!]

If you think that’d help, I’ll hold your beer

 

[browndalton]

What’s the head stamps on the cases?

 

[BHPSteel]

What are the diameters of both of the sections?
Any signs of rifling on the forward section of the case?

A 223 jammed into a 9mm carbine with half the case into the rifled barrel and the back half in the chamber?

223 jammed into a 22-250 chamber?

OK, so the upper part of the case is resized back to 223, the lower part is - what kind of diameter?

223 runs from .376 at the case head, up to .354 just before the neck
22-250 runs from .467 at the case head, up to .414 just before the neck

The case head to shoulder lengths are very similar, and the bullet diameters basically the same

If your brass size down by the head is darn close to .47, that's a possible explanation. Slamming a 223 into a 22-250 chamber with a bit of force is probably possible (the shoulder angles differ a bit so the trigonometry of where the shoulder cone would hit the chamber is a little uncertain) and it might just be in tolerance for the action to go into battery. I can't imagine that the extractor would work though. And needless to say, I wouldn't want to be the dude holding the gun.

Edit: there are actually lunatics out there who seem to have directed other shooters that you can do this.

You are being redirected...

 

[Freshly Minted Georgian!]

I’ll grab one I didn’t resize and take measurements