Questions about military 300 Winchester Magnum chambers. Both vintage and current.
Recently came across a box of 400 pieces of FC 08 300WM brass I bought at least 10 years ago. After sizing with a Redding body die it will not chamber. I will need to buy a Larry Willis collet die to use this brass in a normal 300WM chamber. Out of curiosity I measured a few pieces of this brass and found that they must have been fired in a very loose chamber with most of the body some 3.5 thousandths larger in diameter than the SAAMI max allowable spec. No indication of over-pressure was found with the primer pocket, base or belt diameter.
Just above the belt the brass measures 0.518". Allowing .001" for spring back the chamber probably is something like 0.519" in diameter. SAAMI spec for that spot is 0.5136" with a tolerance of +.002" and I found the same amount of oversize at .2" below the shoulder. The base of the shoulder was in spec.
So here are the questions:
Are overly sloppy chambers like that the field fix for over-pressure rounds in extreme heat? This ammo was loaded in 2008 so they were MK248 mod 0 with the 190 SMK .
I have never heard of such a reamer so I suspect someone was using a tool that could have been anything from a stick with sandpaper wrapped around it to a flex-hone from Brush Research. This explains the fire once and toss policy.
Bonus questions: If there was such a reamer, what is it's name or nomenclature and where can I get one?
Last questions: Do some of the MK13 rifles and other vintage rifles have such a loose chamber? Exactly which reamer was used to build the MK13? Perhaps the standard A191 is not the correct reamer for the MK13 after all? Is the military version of the reamer for the MK248 mod 1 also extra loose like this?
Probably too many questions,
thanks in advance,
Bob
Recently came across a box of 400 pieces of FC 08 300WM brass I bought at least 10 years ago. After sizing with a Redding body die it will not chamber. I will need to buy a Larry Willis collet die to use this brass in a normal 300WM chamber. Out of curiosity I measured a few pieces of this brass and found that they must have been fired in a very loose chamber with most of the body some 3.5 thousandths larger in diameter than the SAAMI max allowable spec. No indication of over-pressure was found with the primer pocket, base or belt diameter.
Just above the belt the brass measures 0.518". Allowing .001" for spring back the chamber probably is something like 0.519" in diameter. SAAMI spec for that spot is 0.5136" with a tolerance of +.002" and I found the same amount of oversize at .2" below the shoulder. The base of the shoulder was in spec.
So here are the questions:
Are overly sloppy chambers like that the field fix for over-pressure rounds in extreme heat? This ammo was loaded in 2008 so they were MK248 mod 0 with the 190 SMK .
I have never heard of such a reamer so I suspect someone was using a tool that could have been anything from a stick with sandpaper wrapped around it to a flex-hone from Brush Research. This explains the fire once and toss policy.
Bonus questions: If there was such a reamer, what is it's name or nomenclature and where can I get one?
Last questions: Do some of the MK13 rifles and other vintage rifles have such a loose chamber? Exactly which reamer was used to build the MK13? Perhaps the standard A191 is not the correct reamer for the MK13 after all? Is the military version of the reamer for the MK248 mod 1 also extra loose like this?
Probably too many questions,
thanks in advance,
Bob