Home Forums Reloading Big Game Rifles 7mm rm mag questions

hey guys i new here and im a bit confused . ive been reloading for about 5 years now and i have 2 7 mags ive been playing with . ive been shooting 140 gr sierra game kings and speer 145 gr boat tails mostly with imr 4350 and fed 215s . im shooting 64 grains and these loads shoot awesome , pretty much one hole at 100yds . i was looking up data last night and wonder why there is so much load data difference and speed difference from book to book . for example nosler shows 65 gr max with imr4350 and another book says 60 gr max . and the speeds will be 2930 in one book and 3280 in noslers book . so i guess my question is what is the best way to find the max load in a rifle when you run across this problem . would it be better to use a chronogragh to try and get to the speeds shown in books or what ? ive never chronoed any of these loads but as far as i can tell there is no signs of extreme pressure in either gun . the primers look good , ive loaded most of the cases 4 or 5 times already , and the bolt is easy to open . any suggestions are appreciated .