I need a little help here. I have a Model 70, 243 Win. w/4x-12x40 scope. I hunt whitetails and coyotes with it. Maximun distance on either one would be 400 yds and more than likely less than 300 yds. I am going to stick to the 85gr. or the 100 gr. at the present time just due to the availabililty at any gun store. What grain would be the most versatile and what would you sight it in for? And last, is there a possiblilty of using BOTH bullets and just switch them out for whatever game I am after?