300 gr bullets are better for long range shooting because of the better ballistic coeffecient of the heavier bullets, for instance a 300g sst(bc of .250)launched at 2000fps hits only ONE INCH LOWER at 300yds than a 250gsst (bc of .210)launched at 2100fps. Yeah, I know thats a little lower with the slower heavier bullet, but the wind drift is what you need to worry about long range ML'ing. You get 4" less wind drift with a heavier bullet in 10mph crosswind. Thats not all, a 250g bullet only has 780 ft/lbs energy left at 300 yds when lauched at 2100 fps(very hot bp load). The 300g bullet retains over 1000 ft/lbs energy at the same range. The differences can be greater than that with a premium bullet such as the barnes original semi spitzer 300g(bc of .290). Past 200 yds with a Ml, knowing the absolute range and wind is critical to good shot placement, better take a good rangefinder.

You also have to put alot of range time to figure your shots, I'm cheating(using a savage w/ ballistic recticle scope), so I can get higher velocities(2150-2300fps with 300g) and it still takes alot of practice to get good at long shots. I'm good to 300, but still trying to get good enough to make a 350 yd shot(everytime). Its alot harder to get that 50 yds than you might think and keep them all in a 5" circle.