A couple of weeks ago I posted this pic and the general consensus was incipient case head separation. This has now happened 4 more times. All the brass is 3 times fired and FL sized brass. The gun is a rem Mohawk 600 .308. We made a dummy round , with the bullit just barely seated. When this cartridge is chambered it barely moves. So it would appear that if the bullit is seated by the manuals OAL , there would be a lot of jump, Is this gun wore out?
Is it incipient case head separation or something else.
- Thread starter Brianma65
- Start date
How many rounds are through the barrel? If it has been shot a lot, the leade may have advanced down the bore. Or perhaps the barrel was long throated in manufacture. Not an issue if the level of accuracy is acceptable. A .308 should be good for at least 5 -10,000 rounds.
This is nothing to do with incipient case separation.
This is nothing to do with incipient case separation.
View attachment 43215The dummy cartridge measured .3036 OAL. Here's a pic of the case, from looking at pics , incipient case separation , happens closer to the case head. These are separating about a third of the way up. The gun is about 60 yrs old , so maybe it's shot out. But it's only a hunting rifle.
If it will shoot 1 1/2 with handloads it isn't shot out.
I think that batch of brass has had its day.
I can remember 600s being sold in the 70s. Doubt that the rifle is 60 years old.
Incidentally, a 600 is a really good rifle. Folks didn't realize how good they were until after they were discontinued.
I think that batch of brass has had its day.
I can remember 600s being sold in the 70s. Doubt that the rifle is 60 years old.
Incidentally, a 600 is a really good rifle. Folks didn't realize how good they were until after they were discontinued.
yes to this
He also has the RCBS Precision Micrometer for .308 but he is a hell of a long way from Newfoundland.
I realize that but with this being a bolt action rifle there is a good chance that the brass is simply being over worked.
A Cartridge Heaspace Gauge will tell him if the fired brass is stretched beyond spec and a Cartridge Comparator can help him setup the full length sizer die for a 0.002" - 0.003" shoulder bump.
You need to have the right tools to do the right job.
Take the bullet out of the dummy case. Headspace has NOTHING, NADA, ZIP to do with the bullet or the OAL of the complete round.
Headspace is only concerned with the distance from the case head to the middle of the case shoulder. OAL of the brass is not involved.
It is entirely possible to overstretch the case if you are excessively sizing it. You need a headspace gauge so you can measure the headspace of a factory round and then compare that to the measurement of your fired round as well as a sized case. You should set your sizing die so that it produces a headspace that is a few thousandths of an inch less than a fired round.
Keep in mind that headspace should not change with use. The only thing that changes with use is the leade or throat and that has no effect on headspace.
Headspace is only concerned with the distance from the case head to the middle of the case shoulder. OAL of the brass is not involved.
It is entirely possible to overstretch the case if you are excessively sizing it. You need a headspace gauge so you can measure the headspace of a factory round and then compare that to the measurement of your fired round as well as a sized case. You should set your sizing die so that it produces a headspace that is a few thousandths of an inch less than a fired round.
Keep in mind that headspace should not change with use. The only thing that changes with use is the leade or throat and that has no effect on headspace.
Is there a way to do this without the gauge. Can my friend use a once fired case from his gun?i should say , I've only been reloading for a yr. The gun belongs to my friend ,who reloads with me. I was asking , to make sure this is not dangerous for him.
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Brianma65
A case head separation will occur at the transition point between the harder and thicker base of the case and the softer upper body. And most separations do happen lower on the case but the separation point depends on the hardness gradient, case diameter, chamber diameter, etc.
Below is a animated image of the rear of the case stretching to meet the bolt face when fired
Head clearance is the distance from the rear of the case and the bolt face and this is how far a case can stretch when fired.
Below look at the red dotted line, for a custom fit to your chamber you adjust the die to push the shoulder back approximately .002 below the red dotted line. The instructions that come with your die has you pushing the shoulder back far enough to fit in "ANY" chamber. And when you push the shoulder back too far during sizing you can greatly shorten your case life as you have done to your .308 cases.
Below a Hornady case gauge and a fired case from my AR15 rifle.
Below the same case above after full length resizing and pushing/bumping the shoulder of the case back .003.
Below are .308 cases fired and reloaded until the cases failed, as you can see with minimum shoulder bump these cases lasted a long time.
Bottom line, you do not have a rifle problem, you are over resizing your cases and they are not a custom fit to "YOUR" chamber.
