ihmsa forums

It has been years since I shot IHMSA. As I was going through and doing my annual "Clean and oil everything" I was looking at my XP's. At some point I bought a gun from another shooter that has a barrel marked "7BR .308ND". Unfortunately I seem to have lost all records of this gun. I understand the 7mm BR part, but I am not sure what the .308 neck diameter mark means. I have not been able to find any information on this cartridge. Does anyone have any info on it? Thanks!

the .308 neck diameter was used to show for a tight necked chamber. on yours, just subtract .284 (bullet diameter) from .308 neck, this leaves .024 for neck thicknesss and expansion. standard Remington 7BR brass ran between .011-.012 thick necks, which leaves 0-.002" expansion during firing.

it is basically a standard 7BR chamber with a slightly tight neck.

Thanks for the detailed description.