More on what greyfox said, when comparing factory and handload velocities you don't know what capacity the factory case is. I have a 5 grain difference on case weights in one batch of 250 Hornady 6.5 creed cases. That alone could cause higher or lower velocities, charge weight and pressure signs. My rule of thumb is if I hit book velocities with book charges with no pressure signs stop! If I hit it with lower charge and no pressure signs stop!if I don't hit it with book charges and I have no pressure signs I change brass first, then primers and work up again.