Ahhh... I got you... Its an airsoft. No wonder. I don't consider them guns, they're just play toys I own an airsoftpistol myself. The reason why I assumed it was an AR-15 is becausecivilians generally aren't to haveM-16s. Here's how you decide an M-16 between anAR-15 in actualrifles:

Who is the manufacturer of said firearm?

Is it fully automatic? Does it have fully automatic capabilities currently installed? Did you pay the BATF for the certification to become a fully automatic holder? Do you have the stamp on the weapon?

Does it have a lug for abayonet?

Does it have threads for a flash suppressor? Threads for a silencer? Do you have the BATF stamp on the silencer?

Did you purchase it directly from a Military firearms dealer?

What year was it manufactured?

Where was it manufactured?

If it doesn't meet the above requirements then its an AR-15. Civilians are generally not allowed to own, purchase, or possess an M-16 unless purchased directly from Military Arms Dealer, is an antique, or have the proper certifications and have paid the necessary taxes, REGUARDLESS OF WHAT STATE YOU LIVE IN. Aren't gun laws just the best?

However, a rifle may meet some of the requirements, such as having a lug or threads for a suppressor, and is still an AR-15. Really what throws it over the edge is the ability to go fully auto. The lower receivers are milled differently internally making it almost impossible to switch an AR to an M.