What is this?

[JDBraddy]

I fired a round yesterday, and noticed smoke from around the bolt, it was difficlut to lift the bolt handle, then the case came out in two pieces (see picture below). This was not a hot load, 7mm-08, 150gr SMK, 42gr Alliant 2000-MR, Fed-210 primer, 2.800-OAL, Remington brass, chronographed at 2,634fps. When I went home, I examined the brass, it looked like it had been cut in half with a band-saw. I looked at the rest of this lot of brass. It's not new brass, it started out as factory ammo, and has been fired and reloaded six or seven times. Out of a hundred pieces, I found about twenty that had a visible ring of discoloration at about the same point where the seperation occured. I've been reloading almost thirty years now, and have never encountered this before, what is it?

 

[jonbearman]

Incipient head seperation at its best. It can be caused by headspace or oversizing mostly.

 

[jonbearman]

Explain in detail how you set your sizing die up.

 

[ShootDots]

Looks to me like excessive headspace problems and the brass is S-T-R-E-T-C-H-I-N-G just above the web area>>>right where most brass breaks in the case of excessive headspacing....

 

[signut]

Headspace problem. Scrap the brass with the ring that you are seeing; it's going to separate most likely on the next firing. You are either resizing the brass too much or the rifle has a headspace issue.

 

[JDBraddy]

Explain in detail how you set your sizing die up.

I'm using an RCBS full length die, I used an RCBS micrometer to measure, and adjusted the die to where it bumps the shoulder back about three thousanths of an inch on a fired case. The case necks have been turned to a thickness of 12 thousanths of an inch.

 

[jonbearman]

If you have rcbs dies for instance,they say to set the die till it touches the shellplate and a 1/4 trun more to cam the press over.This is incorrect as shell plate thickness can vary quite a bit as well as the die.If it is new brass that will chamber,neck size to make sure the necks arent bent or dented slightly. If it is fired brass(once) you should see how it chambers after firing.At this point if it chambers you need to back the die off a turn or so and basically do a semi neck size.If you full length size without trying the chambering feel then you are setting the shoulder way to far back causing excessive headspace.

 

[jonbearman]

Did you fire the original new brass and is it a remington rifle.

 

[JDBraddy]

Headspace problem. Scrap the brass with the ring that you are seeing; it's going to separate most likely on the next firing. You are either resizing the brass too much or the rifle has a headspace issue.

About a week or two ago, I was cleaning this rifle and my identicle .308 Win, and had the bolts lying side by side, it's possible I might have gotten them confused, and put the wrong one back in each rifle, could this be the cause.

 

[jonbearman]

Yes.Check the serial number to match them up.

 

[JDBraddy]

Did you fire the original new brass and is it a remington rifle.

Yes, I fired the original new factory ammo, and yes, it's a Remington 700.

 

[JDBraddy]

Yes.Check the serial number to match them up.

Where would I find the serial number on the bolt?

 

[jonbearman]

Look under the bolt handle or the bolt body.

 

[JDBraddy]

Look under the bolt handle or the bolt body.

I just examined both bolts, both have a "C" on the under side of the bolt handle, but neither have any other numbers or markings that I can find.

 

[jonbearman]

Right next to the bolt handle on the body it should have 4 numbers lazered or done with an electric pencil.How old is the rifle?

 

[JDBraddy]

Right next to the bolt handle on the body it should have 4 numbers lazered or done with an electric pencil.How old is the rifle?

The .308Win was bought new just over a year ago, the 7mm-08 was used and taken in trade, less than two months ago, and I am not sure of it's age. I re-examined both bolts, and am unable to find the 4 numbers you describe on either of the bolts.

 

[jonbearman]

They are opposite the top side of the bolt body and you will need a magnifying glass to see them if they havent been rubbed off.Just take both rifles and go to a competant gunsmith and have him check the headspace with each bolt in your rifle and then mark them when it is straightened out.

 

[Nomad47]

If bolts were swapped and that caused excessive headspace in one rifle, then the other rifle should have too little headspace and should be difficult to chamber a round.

 

[JDBraddy]

They are opposite the top side of the bolt body and you will need a magnifying glass to see them if they havent been rubbed off.Just take both rifles and go to a competant gunsmith and have him check the headspace with each bolt in your rifle and then mark them when it is straightened out.

That sounds like the safest plan, will take both rifles to a gunsmith, and have them checked and marked, and will use the cases that have a visible ring to reset my sizing die to bump the shoulder a thousanth or less, and then discard them.

 

[DennisH]

I had the same issue one time.

Headspacing was my cause.