Yesterday myself and two relatives were partaking in our annual Christmas shoot- mostly offhand can and rock plinking in a pit. One of the rifles was my pre-64 M70 375H&H, a fairly new aquisition that I have put maybe 80 rounds through. I was out of the Rem factory 300gr A-Frame load that the rifle loves and wanted to shoot up some Fed High Energy 300gr Trophy Bonded loads I had. Factory loads purchased 3-4 months ago.

We took turns shooting the rifle 3 times each, then policed the brass. I was putting the rounds back in the carriers when I noticed a case that was split from the mouth to past the shoulder. Sh*t! 3 more cases had splits less severe. 4 out of 9 split. I have shot some of this same HE ammo and not had a problem. Firing and extraction felt normal. Checking out the rifle I noticed the bolt face has some verticle "scatching" or scoring on it that was not apparent before-the fired primers carry the imprint of the scoring on them. Thoughts of oversize chambers and excess headspacing came to me first, but then I thought maybe an ammo problem? At least I don't have to second guess MY loading of the rounds.

I will talk to the gunshop where I bought it (used rifle warranty???) but wanted some feedback and ideas before I go.

John

My best guess is that those are not factory loads, but (very bad) handloads put in the factory boxes.

1. Your Remington loads worked fine, thereby showing that the chamber is at least close to SAAMI specifications?

2. For the primers to carry the pattern imprinted from the bolt face requires excessively high pressure?

3. Normally the brass near the neck and shoulder is too soft to split like that in a chamber anywhere near normal dimension. It just stretches out to match the chamber. This suggests the brass had been work hardened by some defect in the reloading process or multiple reloadings?

4. Given two different defects in the same batch of ammunition (overpressure plus crummy brass) the likeliest conclusion is dangerously amateurish reloading?

Got any ammunition left? Send some to Federal and keep some.

SDS,

I am sure it is factory stuff. I bought it myself from my gunshop, perfect box and carriers, proper bullet, factory crimp, etc. I have 9 or 10 rounds of the ammo left. I'll give Federal a call and see what they say.

John