ok, removed scope, checked all the mounts, everything was fine, thought one ring may not be down all the way but it makes no difference, its still a lil over 4" high at 100.
I took a sheet of osb and stood it up at 50 yds clamped the rifle in a rest with ret on the 48" mark and could easily turn the up adjustment to wath the crosshairs move off the bottom of the sheet.
Not sure whats going on but I'm thinking a 0 MOA base will cure the problem.
Oh and while I was at it I shot 3 for a group at 100. fireform loads off a bipod went into .567 so kirby done good.
While I'm thinking about it how much difference should there be in base thickness from front to rear in a 20 MOA 2 pc base ON A REM 700 la? thanks for your replys!
JS