the STW that I reload for doesnt like lighter bullets, when you start loading the 139 hornady's accuracy goes out the window, Im sure the 7 ultra is the same because of the high velocity
My own 7mmstw's shoot best with the 140gr ballistic tip.They average 1/2" groups with a muzzlevelocity of 3500fps.
as far as recoil a good brake will take that out of the equation.
Install a good recoil pad,forget the brake and save your hearing.