I was just looking thru the new 5th edition of Sierra's manual I just bought and noticed some surprising changes from the previous 4th edition. (50th Anniversary Edition) I have only looked at one caliber so far. 7mm-08 4th edition: 150gr MatchKing, IMR 4064 Powder: Starting load is 36.1 grs. Vel 2300 fps Max load is 42.1 grs. Vel is 2750 fps 5th Edition same bullet and powder: Starting load is 35.1 grs. Vel 2400 fps Max load is 39.5 grs. Vel is 2700 fps Note that they dropped the max load by 2.6 grains! 4th Edition 168gr MatchKing, IMR 4064 Powder: Starting load is 32.2 grs. Vel 2200 fps Max load is 42.0 grs. Vel is 2700 fps 5th Edition same bullet and powder: Starting load is 31.8 grs. Vel 2200 fps Max load is 39.2 grs. Vel is 2600 fps Again a big drop (2.8 grains) in the max load listed. Does anyone have any ideas as to why Sierra has done this? Here are my theories and I would like to hear what you think of them or put forth your own. /ubbthreads/images/graemlins/smile.gif 1) The data for the 5th edition was made using a different test barrel. Probably new and with tighter dimensions resulting in higher pressures for a given charge of powder. 2) When Hodgdon bought IMR in 2003 the burn rate of IMR 4064 powder changed somewaht due to different processes used. Since Hodgdon didn't buy IMR until October of 2003 and the 5th Edition of Sierras manual was published in 2003 I don't think this is the cause, but I could certainly be mistaken. 3) Damn lawyers told them to knock back the charge weights due to our law suit crazy society, which was caused by damn lawyers in the first place. /ubbthreads/images/graemlins/crazy.gif Note that they have knocked back the max charge weights on almost all powders for the 7-08, not just 4064, by a substantial margin. Another note is that I just looked at some loads in .270 Win that I have used for quite a while and they do not seem to have changed at all. Maybe theory #1 isn't that far off base.