Frank, are you crimping the bullets in place or relying on neck tension only?

Almost of all of my barrels and calibers I do not crimp. However, with a 22-250 1-12" twist barrel (I recently let go to a buddy) if I just seated the bullets with no crimp I would get .75" @ 100yds reliably, but if I would give them a light squeeze in a Lee Factory Crimp Die it would instantly shrink the group to the .250 to .375" range. Maybe something to try if all else fails.