The perpetrator of the horrific mass shootings in Lewiston, Maine, does not appear to have used an AR-15 in his attacks, but instead an AR-10-style rifle, according to law-enforcement officials. However, an AR-15 was found near the shooter’s body, according to law enforcement.
Eugene Stoner, the inventor of the much more popular AR-15 in the 1950s, first created an AR-10. The AR-10 fires a larger and more powerful round than the AR-15. As explained in American Gun: The True Story of the AR-15, the U.S. military rejected the AR-10, after it failed critical tests. After the rifle failed important tests, an Army general, Willard Wyman, secretly visited Stoner at his office in southern California and asked him to make a gun very similar to the AR-10 — but with a smaller caliber. Thus was born the AR-15.