Pressures getting too high, tight/stiff bolt lift after firing, flattened primers. I've often found starting loads to be accurate, opening up a touch mid-range then tightening up again at the higher end loads. This is my experience with my own rifles & particular loads & as is often stated you must work up to suit your own components & rifles - change any component such as primer & case and it's safe practice to start again
(CZHOWA beat me to it)
(CZHOWA beat me to it)
