Besides the Dominican AP which would void your warranty (only ammo they mention as such as far as I know), you also generally can't shoot SLAP or SLAP-T rounds.
These rounds are sabots with .30cal heavy tungsten penetrators. SLAP-T is the tracer version. The usual myth is because they get caught up in the muzzle brake. This is untrue. You can fire them without problem using the muzzle brake. However, the barrel must be cut for it. The military saw signs of overpressure when firing the high pressure SLAP/SLAP-T. Barrett sells a barrel specifically cut (chamber I guess) for that round and the military has bought them. I got this information directly from Barrett.
Oooh! I see a M82A1 with the SLAP barrel for sale! (Goodle)
However, the rarity of the SLAP rounds is such that you probably won't ever have any unless you are a collector. It's rare and more than $40-$45 per round last time I even saw it for sale, which I almost never do.
I sure would like to see what it can do, I understand it is supposed to be able to penetrate several inches of steel??? Because it can extend the range of AP effect to 1500 feet, is it not such a penetrator as a range extender for AP effect? SLAP velocity = 3985 fps