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Case Seperation

1768 Views 15 Replies 8 Participants Last post by  George Foster
I am wondering what would cause a case to seperate 11/16" up from the base. The case will seperate I know on the expansion ring if stretched too much or from excess head space.
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6mm Rem, Rem Brass. Reloaded twice.
What I am asking is why the case seperated 11/16" up the case, NOT at the expansion ring. There are other cases with the ring in the same place that will seperate if fired I believe.
Here is the story, I had a gunsmith rebarrel a Rem 700 with a Douglas 6mm Rem barrel. I have to overcam the die by 1/4 turn to even get the case to fit into the chamber. I have tried factory new cases and the don't fit. I personally feel the chamber could be cut short but I don't know. I have approximately 100 rounds through the barrel. I took the rifle to the gunsmith last Tuesday after a round seperated in it. He has it now as he said he didn't know what could cause the problem.
recoil junky,

You are thinking the same thing as I am about the short chambering. Yes it is the same gunsmith as I feel if it is the chamber he should fix it, I asked specifically if he chambered the barrel or got it short chambered. He told me he chambered it. When I took it down last Tuesday is when he told me he didn't know what would cause it, this was just standing there talking to me without getting the case out of the chamber or anything.
I talked to my gunsmith a bit ago and he has found the problem and fixed it. It seems the diameter of the chamber was the bare minimum SAMMI measurement, the length was okay.
He polished the chamber to the proper diameter so it should be okay.

Go /No-go Gauge
This is what a set of .308 Winchester Go/No-go gauges look like. They are designed to verify that chamber headspace is within the SAAMI spec tolerance from the base of a case to its shoulder. It's best to use them after removing the ejector on most rifles, so that you can "feel" these gauges as they are chambered. These gauges help you verify that any factory loads should fit in your chamber, and be safe to fire.

When reloading, it is important to always bump the shoulder of your cases back at least .001" - .002" to ensure a reliable fit in your chamber. There is no accuracy gained by crushing a cartridge into your chamber. This affects the concentric alignment in a negative way, and it can wear the lugs of your bolt. Keep in mind that most necked cases are tapered, and the wall of your case should never press against the chamber.

Not all chamber reamers are perfect; and as they begin to wear out, they will cut tighter chambers. A set of these Go /No-go gauges will rarely detect the work from a defective or worn chamber reamer. This is because headspace gauges can't check the width of a chamber.

I have examined custom chambers that checked out perfectly fine with Go /No-go gauges, but these chambers had "excessively" tight body diameter. Match chambers are always a bit tighter at the neck and usually require handloaders to do some neck turning, but the rare tight chambers I'm referring to were actually too tight (diameter) at the body. In some cases they caused cartridges to jam tight against the chamber wall and fail to chamber.

The case width problem is commonly overlooked. Handloaders often find that belted magnum calibers seem to have the most case width problems, but that's caused by a different situation. It's partly due to the limitation of conventional resizing dies when handloading a case with a belt. Just keep in mind that a Go /No-go gauge is only designed to detect headspace (length) problems, and remember that "case width" is also an important consideration.
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The case didn't seperate where the normal stretched case does and the go/no go gauges didn't show any problem. The only thing I can think of is the over resizing caused the problem. Yes the rifle is fine now and everything is working as it should.
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