They should be but check with someone that lives in your State, the worst question is will the range allow you to shoot them at their targets. Most ranges frown on 50 BMG rounds because they're all steel core if they're surplus and will go through mild steel, even 50 BMG ball has a steel core that will rip right through steel targets. The API is another issue also as there's the chance for fires getting started from the incendiary mixture.
It gives 50 BMG shooters a bad name when we just show up and start shooting at the ranges targets and ruin them, match rounds like AMAX and brass solids just leave a big splat mark on steel and wont pass through. For best results, call your local range and see how they feel about 50 BMG's and what type of ammo they'll let you shoot at their targets.