I think you'll find that 500 yd accuracy figure that you mention is not really practical. Will the 55 or 62 grain bullet make 500 yds? Yes. Can it perform accurately to 500 yds? Yes, see the Camp Perry results. Will the bullet have the velocity required 2500 fps to make the mil ball perform properly on a human at 500 yds? No. Run the numbers through one of the ballistic calculators on the WEB. For instance the 16" M4 will only perform reliably to about 150 yds.