Assault rifles are rare and expensive, but legal in most states. They are tightly controlled at the federal level, and no new ones have been allowed since 1986.

Armor piercing rounds are legal to sell, purchase, own and shoot. Steel-core rounds are illegal to manufacture or import.

Teflon-coated rounds are a fantasy. They exist, but do absolutely nothing to make them more effective - instead, they are intended to extend the life of a gun's barrel by limiting wear.

Tanks are not illegal. Armed tanks are also not illegal, provided the main weapon is registered as a destructive device, along with any active explosive or incendiary rounds for it. Training rounds are (e.g. chalk) are unregulated.

I oppose all firearms regulation, period - but let's get our facts straight. :)