new 270 case rupture

[turner]

Hi folks - Not exactly a reload question but I'd appreciate your expertise.

I'm a retired guy. I've been shooting and reloading since the early 80s - 22.250, 44 mag, and 9mm, (and shooting rimfire). I've just started shooting again after a long hiatus. My son moved back and he's re-energized me.

He went out with a friend, a novice shooter, today to help him with basics. They were firing a brand new Remington 700 in 270. They had 6 boxes of new factory ammo, 150gr, same lot.

The 14th round split the case down near the base! Shooter got hit with blowback. The fired cases have the shiny band. Primer looks ok.

Any advice appreciated.
tia

 

[spclark]

Doing a quick search I ran across this:

http://cheaperthandirt.com/blog/?p=22277

- so if that factory ammo fits the description in the recall notice it's UNSAFE TO USE.

Otherwise I'd have the headspace checked by a competent gunsmith first thing.

When you say "shiny band" do you mean a ring on the fired case sides just in front of the extractor groove, pretty much the same place the one case actually failed? That's a bad sign, those cases are stretching too much when fired.

 

[turner]

yes, all fired cases have the the ring 1/8th ahead of the extractor groove.
unfired measure .46390 - .46445
fired measure .46980 - .46995
Sure looks like excess headspace.
thanks

 

[243winxb]

These measurement, unfired measure .46390 - .46445
fired measure .46980 - .46995 of the web area, have expanded about .006" The correct area to measure for over pressure is in the extractor groove, i think??? The case seems to be stretching. Measure the head to datum line before & after firing your new factory ammo. If more than .010" excessive head clearance may be the problem. Lots of factory ammo will give a lot of slop in the average chamber. http://www.saami.org/PubResources/CC_Drawings/Rifle/270%20Winchester.pdf

 

[spclark]

The correct area to measure for over pressure is in the extractor groove, i think?

That's where I measure when looking for pressure, where the case head metal's deforming while unsupported and where metal movement away from the primer pockets will drastically affect case life.

Visible stretch bands at the case web, in fact anywhere ahead of the extractor groove, is a worrisome sign: it's not supposed to be happening.

 

[turner]

They took the gun to a gunsmith and it checked out just fine. And no damage.

It is the ammo. He called the manufacturer a supplier of 'crap' ammo. He's seen many problems with them and it's one of the big names! There were rounds that wouldn't chamber too in this lot.

I don't have a lot of experience with factory stuff, or this type of problem, as I'm still reloading my 30 year old federal brass.

Thanks for the input.