Case head separation/barrel reuse question

N

Nukalpiaq

Inactive
I am considering building a rifle using a Winchester 70 Classic SS 300 Weatherby magnum action and instead of buying a custom barrel I am considering using a factory barrel from a Winchester 70 Classic SS 375 H&H, the owner said he removed the barrel from his action due to a case head separation. I would like to find out what I should be looking for when I inspect the barrel or should I have a gunsmith inspect it for me ?
From my reading I found out that one of the main reasons for this type of problem is due to excessive headspace, basically the factory's chamber reamer may have been a little worn out when the rifle was manufactured. I also read that a barrel could be reused but it would need to be set back and rechambered to tighten the tolerances. Another reason I read about for case head separation could have been due to the lugs and seats being worn or issues with reloading the ammo. I am still making my inquiries, so the exact problem is yet to be determined. My question; Is the barrel still safe to use and does anyone have any experience with reusing a barrel like this before? Thanks
 
A case head separation would lower, not raise, pressure in the chamber and bore. Could be that whatever caused the separation could still be a problem, but, if you headspace the barrel correctly, you should be o.k.
 
With a used barrel, getting good headspace is a crapshoot. You might luck out and it will be fine, or you might have to ream the chamber if headspace is too short. If it is too long, then you will probably have to set the barrel back. With a Magnum case, headspacing is from the bolt face to the chamber shoulder that supports the belt. But, you also have to make sure the chamber allows the right room for the case shoulder, even though the case does not headspace on the shoulder like, say, a .308 Winchester.

The problem with belted cases for reloading is that the belt provides a right-angle stress point that is very prone to separation if there is even a slight headspace problem. The reason is that, like other cartridges, excess headspace allows the rear of the case to back up under pressure while the front of the cartridge is sealed to the chamber walls by the pressure.

In a cartridge like the .308, there is a stretching of the case which can cause or lead to case separation. The same is true with a belted case, but with the latter, there is a stress riser in the right angle of the belt, providing a weak point which will be there no matter how reloading is done.

Jim
 
Thanks for providing some feedback, all your responses have helped me to better understand what case head separation actually involves and what may have been the root cause. Personally I have never had this happen to any of my cartridges since all I have shot to date are factory loads and I do not reload.
A respondent from another forum addressed an earlier comment I made regarding the worn chamber reamer and excessive head space problem, he stated a worn chamber reamer would result in insufficient headspace, not excessive. This sounds logical and correct.
The primary reason I wanted to use an original Winchester barrel is to preserve the identity of the rifle as a Winchester 70 Classic SS, additionally I thought I would be able to save a little time and money on the turn around. I am starting to see that there may be some precision barrel work involved in getting the correct head space and additionally to insure that the barrel lines up correctly for proper sight and extractor slot alignment.
My main concern with using this barrel was safety, since I would be the one carrying the rifle in the field. Since most respondents agree that the barrel and chamber would not be damaged by a case head separation then I am convinced that the barrel will be safe to re-use. The owner has offered to have a gunsmith check it out before selling it to me. I will decide after I get the gunsmith's report.
Nukalpiaq

Here is an excerpt from the owner's response to my inquiry regarding the cause of the case head separation.

Quote: I'm convinced it was caused from weak/over-annealed brass. The load was a starting load for the bullet and powder combination...using rounds that I loaded for a trip a couple years prior. I pulled all the bullets in that batch and verified powder type and weight...all the gas and pressure came back through the action...There have been less than 100 rounds down this barrel.
 
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case head

Sir:
"Case head separation" usually doesn't result in a blown up gun!
Case head separation happens over a long period of time by improper reloading practices - but it, if it is great enough result in a blown up rifle.
When a cartridge is fired the primer strike (if there is excessive headspace) pushes the case forward - when it goes off the case walls grip the chamber walls and the pressure causes the brass to stretch and go back and stop at the bolt-face hence causing a small stretch area in the close proximity of the head. If, through improper reloading practices the cartridge is full length resized as die manufacturers instructions tell you (incorrectly) the same thing will occur each time you shoot it and eventually you will not only hace incipient case head separation - you'll hace case head separation.!
Now, contrary to popular belief, the "belted magnum" case is the most dangerous case to work with! Yes, after the first shot, we do not headspace off the "belt" but this time off the shoulder of the case. However, if it is a maximun chamber and a minimum case and you headspace off the shoulder you've left way too much just in front of the belt and the fireworks are impressive!
Chambering a belted maggie is involved and the "go" guage must be .220 - no more or less - absolutely because most belted mag. cases are only .216 - .218!
Harry B,
 
headspace on belted mags.

Sirs:
I cannot remember where I read it but I know I did that the British headspace on a belted magnum was .220 go - .222 no-go!
I know that SAAMI specs. are different (and very sloppy) but I feel that the British is coorrect.
I can still see the text but cannot remember where!
Harry B.
 
Mr. Bonar

You expained the magnum case seperation to a post I had made recently. (Thank You) After spliting the case, just above the magnum belt on the lathe, Low and behold... one can clearly see where the case is beginning to seperate. About 1/8th inch above the belt a shiney ring appears on the outside of the brass,but on the inside one can see where the case is seperating and by running a pen across it, I can feel the depression. (maybe a thousanth or two)
Would you mind explaining how you would reload these cases to eliminate the case seperating, possibly in another thread so as not to high-jack this one. I think that would be quite helpful to some of us wanting to produce as safe a handload as we possibly can. :)
 
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