Home Forums Hunting & Shooting Hunting Rifles Mark V 300 Wby magazine to 30-378 magazine length

What is the difference between a Mark V chambered in 300 WBY to one chambered in 30-378. I tried to fit a 378 in the magazine and it is too short? Not being familiar with Mark V actions, I am hoping someone can tell me an easy fix to make this fit. My buddy wants to rechamber his and needs the additional length.

JW This is what I was looking for. It will be re-chambered to 7mm-300 WBY but we want to be about to seat the 180s out to a decent length, hence the 378 length was desired. I will take both apart and compare them and decide how to proceed with the mill...