Different rifles will give you different pressure/velocity results from what is in manuals. I had 2 30-06's, one gave me great MV and decent accuracy at just under max published load. In my other rifle the same load resulted in pressure results like yours, stiff bolt and ejector marks. The load data is developed with TEST Barrels. I would think a test barrel would be selected to be around mid SAMMI specifications for bore and chamber. Neither too tight or two sloppy. In the everyday retail world we buy rifles that have the possibility of being of tighter or looser dimensions than "TEST" barrels, thus we can not expect we can always achieve results that match the published loading manuals.Thank you. IMR 4451 load data shows 41.9 as max load. 39.5 seems like a low charge. How does it arrive at that number.