How to get an M16?

Answer 1

In the US, Israel, and quite a few other countries, you can get an M16 variant if you enlist in the armed forces.

A US civilian in most states can buy an actual M16 from a Class III firearms dealer. The rifle will need to be one registered with the ATF prior to 1986. The transfer will require a background check, approval of a local law enforcement chief, and payment of a $200 tax to the ATF. These rifles are expensive due to limited supply - expect to pay upwards of $25,000 for one.

Also, you can buy an M16 if you become a Class III dealer or make one if you become a licensed manufacturer.

A civilian clone of an M16 (more or less same rifle minus the full-auto capability) can be purchased the same as any other rifle from a gun shop or a private party.