Re: lower velocity/energy limit MK performance on big game
At the velocities you gave, at "700 yards" for both bullets you will have remaining velocity and Foot pounds of energy left of;
A. 129 Gr----1683 Velocity---812 Foot Pounds
B. 140 GrMK--1704 Velocity---903 Foot Pounds
Hope you have the correct twist to work with the 140 Gr, if not the 129gr will do.
The mule deer that Ray killed in Colorado last year at 1800 yards, the bullet had slowed down to a energy level of 800 foot pounds.
From what I read in the game laws, the minimum caliber allowed in Colorado for big game is a 243, you should do fine with the 6.5 when placing the shot well.