If you really think their is not dif. and 100-150fps doesn't matter
have some one load your rifle and put in just one of the light mags
fire all the rounds,you will know when the light mag goes off, good
ammo and i can't say it is all that more expensive, for the dif.
I didn't know i needed some thing bigger than 06 for elk, hope
none of the elk find out, of course i don't shoot over about 350yd
at anything and the 06 will handle elk that far.