My cousin has a Charles Daly 7mm Rem Mag (Mauser Action). He was firing factory Winchester 150 grain loads (grey box). He noticed two fired cartridges had developed cracks in the case body. I'm not sure what caused this and my cousin lives some distance away so I'm just going on what he told me. Could it be defective factory ammo? or maybe oversized chamber? I suggested that he measure his fired and unfired cartridges with a micrometer, and to clean and inspect the chamber to see if that can shed any light on the problem. Does anyone have any ideas before going to a gunsmith. We had shot the rifle previously (it was brand new) without any issues. The round count is probably less than 150 rounds.

Thanks
Ed

If the chamber is clean and has no marks like that in it,I would have to say the brass is the problem.
I had some winchester brass for a pistol that cracked when loading and out of the ones that didn't some did when shot.
you might run this by the factory and see what they say.

A fellow in another thread got a Remington case w/o a primer hole. He sent a picture to Remington and they are sending him 200 new cases. I wouldn't be surprised if Winchester would do the same.

I should think Winchester would be very interested in seeing the cases, remaining ammo, and the lot number.

It is a stress crack.

I have been shooting Rem 7 Mags since 1977, never seen anything like this.

Two things would cause this:

Extremely hard brass

Oversize chamber firing work hardened brass

Brass defect-thin wall

If you have the devise from www.sinclairintl.com that measures wall thickness, you could determine wall thickness at any point in the case.

If you have two cracked cartridges, why not cut one lengthwise down through the crack and do your own assessment? Save the second for Winchester.

Good idea, I'll get ahold of my cousin to advise him.

tks

Ed