I don't think your chamber has been enlarged, friend.
Some of the VERY early Mark IIs (and yours is VERY early, going by that rear sight) were notorious for their generous chambers.
Rough comments in that direction were one of the reasons that Ross tightened the chambers in later rifles.
Then they b*tchd again!
My built-in-1906 is a twin to yours except that yours is MUCH nicer. I am willing to bet a whole piece of Raisin Pie that our brass cannot be told apart!
It is simply the Nature Of The Beast.
Try backing your die out about half an inch, putting a lubed case on the ram and raising it, THEN screwing the die down until contact plus a quarter-turn. That should size the CASE. For the NECK, swap out your .311 expander for a .308 expander. Should help a lot.
Good luck!
Some of the VERY early Mark IIs (and yours is VERY early, going by that rear sight) were notorious for their generous chambers.
Rough comments in that direction were one of the reasons that Ross tightened the chambers in later rifles.
Then they b*tchd again!
My built-in-1906 is a twin to yours except that yours is MUCH nicer. I am willing to bet a whole piece of Raisin Pie that our brass cannot be told apart!
It is simply the Nature Of The Beast.
Try backing your die out about half an inch, putting a lubed case on the ram and raising it, THEN screwing the die down until contact plus a quarter-turn. That should size the CASE. For the NECK, swap out your .311 expander for a .308 expander. Should help a lot.
Good luck!

































































