Try seating them at 2.280. Also, measure a few that have been in the mag during firing, but not chambered to see if they are growing during recoil. Your neck tension may not be enough. The neck tension becomes inconsistent after several firings if you are not annealing. The crimp die can also cause a reduction in neck tension as it applies pressure on the case mouth. I find that the absence of a crimp is better than the Lee Factory Crimp Die on a bolt action rifle.