The AR-15 is one of the most versatile rifles ever made, largely because of the platform’s modularity.
The AR upper and lower receivers mate together to make the complete rifle.
It’s important to know when you’re in the market for an AR lower receiver, that the lower receiver is the only part of an AR-15 that the BATF legally recognizes as a firearm. That means a few things.
All the other parts get shipped right to your door. A lower, however, must be shipped to an FFL dealer. A Federal Firearms License allows a local gun store to accept the firearm, and then transfer the firearm to you after a background check and the Firearms Transaction Record Paperwork Form 4473 are complete.