Generally speaking, they are all safe for the gun...
In practice, the blue-tip (incendiary) bullets are known to sometimes break up as they exit the barrel.
If that happens within the muzzle brake, it can damage it. In the instances where I've seen it happen, it was several feet out.
Too, the S/T projo was designed to travel at lower velocities than typical .50bmg ammo. Loading/shooting them with heavy loads could be detrimental to the health of the gun and you.
(safe loads in a .50bmg case should be in the 170-190gr of 5010 range....)
If you need bore-rider, or semi-bore-rider bullets, check out http://www.aaa-ammo.com/
If you don't have a chamber cut for bore-rider bullets, then the surplus AP is good for cheap and accurate reloading. If you can't have steel core bullets at your range, then the new Prince-Al M33 brass projos are a good deal. At the high end (2.00 a bullet!), the Lapua 800gr bullets shoot well. (in my BFG anyway...)
Prince-Al M33 750gr
Lapua 800gr