I am planning on hunting varmint and big game (deer size) with this rifle out to 1200 yards I figurd the bullet would have over 600 ft-lbs of energy would this be enugh energy for the deer size game? I would like to use the 142 6.5mm MK would this be a good bullet choice. Sierra has the BC on this bullet at 595 is that correct? The rifle is a hart action with a 1.25 to .900 28in 1-8.5 twist Krieger. What powders should I start with?