We had an old codger shooting a Musgrave on Saturday and about 50% of his cases were separating. He maintained it was not a safety issue and returned to the mound for his second shoot with the same problem.
Is he correct? Does anyone know of injuries etc. having come from case separations. Are some actions (e.g. Musgrave) built well enough that it doesn't matter?
Alan
Case Separation
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johnk
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Alan,
Interestingly, I have never seen an instance where case separation resulted in a noticeable blowback of gas through the action & that includes one case I popped long, long ago before I knew how to load properly. From that, we might surmise either that the separation generally occurs after firing when the case is being withdrawn from the chamber or that the process of combustion nevertheless expands the remains of the case enough to form the necessary seal.
I don't think that action type is an issue here.
However, case separation I believe is a consequence in almost every case of injudice sizing of the fired cases. Once fired, a case conforms to the chamber & in may be resued without any body sizing if other case preparation does not modify these dimensions - which most neck sizing techniques used on standard chambers do. The Lee collet die is the only neck sizing deevice that I have used in standard chambers that doesn't also concertina the body to an extent that warrants resizing.
In any case, full length sizing should only be taken to the extent necessary to permit the case to reenter the chamber freely. Overdone, it introduces headspace that will inevitably lead to case separation.
John
Interestingly, I have never seen an instance where case separation resulted in a noticeable blowback of gas through the action & that includes one case I popped long, long ago before I knew how to load properly. From that, we might surmise either that the separation generally occurs after firing when the case is being withdrawn from the chamber or that the process of combustion nevertheless expands the remains of the case enough to form the necessary seal.
I don't think that action type is an issue here.
However, case separation I believe is a consequence in almost every case of injudice sizing of the fired cases. Once fired, a case conforms to the chamber & in may be resued without any body sizing if other case preparation does not modify these dimensions - which most neck sizing techniques used on standard chambers do. The Lee collet die is the only neck sizing deevice that I have used in standard chambers that doesn't also concertina the body to an extent that warrants resizing.
In any case, full length sizing should only be taken to the extent necessary to permit the case to reenter the chamber freely. Overdone, it introduces headspace that will inevitably lead to case separation.
John
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AlanF
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John,
Thanks for the response. The reason I mentioned the type of action is mainly because of strength. I am no expert, but my understanding is that the friction of the case against the sides of the chamber reduces the amount of force on the boltface, so if a case separates near the head then it could test the strength of some actions?
Alan
Thanks for the response. The reason I mentioned the type of action is mainly because of strength. I am no expert, but my understanding is that the friction of the case against the sides of the chamber reduces the amount of force on the boltface, so if a case separates near the head then it could test the strength of some actions?
Alan
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johnk
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Alan,
I see what you're getting at, but consider that a .308 case head with a radius of around ½" has a surface area of under .2 square inches, so loading to 60000 pounds per square inch, that's still only 12000 pounds thrust on the bolt if the full pressure is directed there. Whan you consider that the internal area of the case head is somewhat less, then there's not a hell of a lot of thrust onto the bolt. About any useful action should handle that - as opposed to the gas cutting that occurs when a case is overloaded & the head expands, breaching the primer pocket.
All the separations I've seen (& admittedly, it's not a lot - I've only ever used my separated case puller once in anger as a RO) were not accompanied by soot around the base of the case or tales of fire & brimstone from the firer, so maybe we're lucky that the miscreants rip the heads off the cases before they get to separation by firing.
John
I see what you're getting at, but consider that a .308 case head with a radius of around ½" has a surface area of under .2 square inches, so loading to 60000 pounds per square inch, that's still only 12000 pounds thrust on the bolt if the full pressure is directed there. Whan you consider that the internal area of the case head is somewhat less, then there's not a hell of a lot of thrust onto the bolt. About any useful action should handle that - as opposed to the gas cutting that occurs when a case is overloaded & the head expands, breaching the primer pocket.
All the separations I've seen (& admittedly, it's not a lot - I've only ever used my separated case puller once in anger as a RO) were not accompanied by soot around the base of the case or tales of fire & brimstone from the firer, so maybe we're lucky that the miscreants rip the heads off the cases before they get to separation by firing.
John
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