Case separation

[df06]

Bought some once fired brass for my 17 hornet.
On my first firing, two of fifty brass completely separated about 1/4” above the rim, when I fired them. Rim and bottoms 1/4” was ejected from gun, front end of brass stayed in chamber but was loose enough to almost fall out.
What the problem?
Not loading hot, 12.5 AA 2200 and 20 grain bullet.

[TonyRumore]

Head Space.

[Nor Cal Mikie]

(Head Space.)?? Not actual "chamber head space", more like brass too short for the chamber. (shoulders pushed back too far) Round fired, case fire forms to the longer chamber than the OAL of the brass, brass in thin about the rim and case separates.
You MIGHT get by if you anneal the brass but more likely, it's toast. Time to buy new.

[df06]

Would new brass and neck sizing only solve those?

[SmokinJoe]

Damage may have already been done when originally fired. I have had a significant amount of trouble with Hornet brass too. Check each case for a bright ring around case at about the point where the other two separated. Bright ring = trash. FWIW, I don't think I would fire brass from another gun in mine unless I could establish that headspace measurement was as long or longer than in my rifle; even then I would closely examine the brass for the telltale bright ring. Good luck with it, I know you are a bit frustrated with this.

[Bill K]

Once fired in the other persons rifle, his chamber is tighter than yours and so you end up with some brass with more shoulder set back and therefor it separates in yours, sort of a matter of it not being head spaced on the shoulder and rim of your hornet chamber.
Best to just get new brass and fire and fit it too your chamber. The ones that you fired and did not separate probably will now fit and be just fine in your chamber, I would not set the shoulders back at all, when you size to reload. Bill K

[df06]

Thanks guys

[dungheap]

If you lost two out of fifty, neck size the ones you did not lose and try them again. There may be something to be said about sharpening and bending a piece of stiff wire to a 90 degree angle, run the pointed end down the case wall. If there is a ring developing (or developed) you'll be able to feel it easily. Those cases should be tossed.

[Hog Patrol]

How much money did you save? It's been my experience buying once fired brass isn't cost effective. Free stuff is though.

[df06]

Will do, feel inside the remaining cases with a bent wire. I’ve done that in the past and found some problem cases.
How much did I save buying once fired, not enough, that’s for sure. I actually don’t recall what I paid for the once fired.