Recently purchased a Remington 700 SPS Stainless .300 RUM with 26" barrel. I have never tried to shoot more then 200 yards so I am very new to long range shooting. I shoot a really good group at 100-200 and really would like to learn to shoot to about 500-600 and maybe even further if possible. I will be hunting mainly deer with this gun with the yearly elk trip. What would be the best bullet for this gun?