If you have ever pulled bullets and weighed powder charges, the variation between cases may surprise you, therefore the difference in velocity you noticed. tho I`m surprised that, except for your first shot, clean barrel?, all velocities were over factory listed.
I would shurly not shoot any more of this box. Give Remington C.S. a call, if my experience holds, they will want the rest of the box for evaluation on their end.
Good Luck
