A 500 A-Square just screams cast bullets at a moderate velocity. If you have one of these, then you will want to shoot it as often as you can, and cast bullets can allow that a bit more frequently, and a bit cheaper than jacketed bullets.

We have a couple of guys in the BGR club here in Australia that have Ruger #1's in 500 A-Square. They shoot a custom CBE lead bullet that weighs, I think, 800 grains with gas check. The bullet was designed for the 50 BMG.
They can easily achieve the 5300 ft/lb minimum muzzle energy requirement.

Regards,
David.