Explanation: The AR-15 rifle is a popular semi-automatic rifle in the United States, which is often customized with aftermarket parts and accessories. The AR-15 is known for its modular design, which allows for a variety of configurations and customization options. One of the most popular modifications is the addition of a "bump stock," which allows the rifle to fire more rapidly by using the shooter's momentum to actuate the trigger. The AR-15 has been involved in several mass shootings in the United States, and there is ongoing debate about the need for stricter gun control laws.
