74A95,
Thanks for the fat finger catch. I fixed it, but can't figure out how I entered the error in there in the first place. Need to remember to reread slowly.
The reason for the minimum case mouth diameter being as large as it is is so that a cartridge lying on the bottom of the chamber still has at least a thousand of overlap at the top of the throat. The concern is that, theoretically, anyway, a hard feed might be able to upset the side of the. case mouth that catches the edge of the headspacing shoulder, thus allowing the opposite edge of the case mouth to be driven slightly into the throat. The thickness of the chamber's headspacing shoulder is 0.011.5", and if you add that to the 0.3580", you get 0.3715". Add a thousandth and a half, and you have at least a little contact all around the clock.
The guns that would have a problem if that criterion wasn't met perfectly are probably mostly in the category of full auto weapons firing from an open bolt. Nonetheless, that is how the dimensions are chosen, AFAIK.
Thanks for the fat finger catch. I fixed it, but can't figure out how I entered the error in there in the first place. Need to remember to reread slowly.
The reason for the minimum case mouth diameter being as large as it is is so that a cartridge lying on the bottom of the chamber still has at least a thousand of overlap at the top of the throat. The concern is that, theoretically, anyway, a hard feed might be able to upset the side of the. case mouth that catches the edge of the headspacing shoulder, thus allowing the opposite edge of the case mouth to be driven slightly into the throat. The thickness of the chamber's headspacing shoulder is 0.011.5", and if you add that to the 0.3580", you get 0.3715". Add a thousandth and a half, and you have at least a little contact all around the clock.
The guns that would have a problem if that criterion wasn't met perfectly are probably mostly in the category of full auto weapons firing from an open bolt. Nonetheless, that is how the dimensions are chosen, AFAIK.