Ar lower with out bullet button

[trowa47]

is a ar lower fully built with out a bullet button a assault weapon or is it just when you add the upper with out the bullet button thanks

[HK Dave]

It's when you add the upper.

For example... if you have a 22lr upper, you can legally have an AR15 lower with no bullet button.

Assault weapons are classified as CENTERFIRE.

[Cokebottle]

Ditto.
It must be either a centerfire, semiautomatic rifle or a semiautomatic pistol (rimfire handguns are not exempt).