dkhunt14 said:That is a lot for one firing. I would guess you got real soft brass; a large chamber or you are too hot. Seeing you are getting that much expansion I would guess a large chamber at back end. Do they keep getting bigger on more firings? Matt
Not hot loads and Lapua brass so I guess it's the chamber. I sent off an email to the rifle manufacturer for comments.
I will measure again after the next firing.
Thanks