"Don't forget the K31's typically have a .304"-.306" groove diameter barrels for that slightly smaller 7.5 mm bullet."
True only for the part of the GP11 bullet that sticks out of the case.
The widest part is right where the boat tail starts.
In other words the GP11 does not have a parallel shank, it tapers ALL the way to the boat tail.
7.5mm refers to the bore(avg ±7.54= .296"), same as you would refer a .308" diameter bullet for a .30 caliber bore.
.308" is actually 7.82mm diameter.
Last edited by diopter; August 2, 2012 at 08:42 PM.