The question is not being asked in the right way. Actually to armadillo, it takes a weapon which may or may not require rounds (bullets). If the weapon with which you armadillo is a gun, it depends upon what type of gun the armadillo is armed with as to how many rounds it requires. For example, a single shot shotgun would require one round. Hope this helps.
Depends on what you are shooting them with...one should do it with the right gun....they are tricky little buggars...always moving so it is EZ to get a glancing blow...;-)