The AR-15, explained — with sources.

Plain-English guides to the AR-15’s history, how it works, common myths, and the U.S. legal landscape. Every factual claim links to the source it came from, and every page shows when it was last reviewed.

Start: how an AR-15 works How we source

Guides

• History

  ArmaLite, Eugene Stoner, Colt, and how the AR-15 became the M16 — with dates tied to sources.

• How It Works

  The semi-automatic cycle and Stoner’s gas system, explained from the original patent.

• Parts & Names

  Upper, lower, bolt carrier group — and which part the law treats as the “receiver.”

• Myths vs Facts

  What “AR” stands for, semi-auto vs automatic, and other common claims checked against primary sources.

• Law

  A neutral federal overview: NFA, GCA, the 1994 law and its expiry, and key Supreme Court cases.

• .223 vs 5.56

  What the industry standard actually specifies for .223 Remington, and what to check on your barrel.

Reference & tools

• Glossary

  Terms like “semiautomatic rifle,” “machinegun,” and “receiver,” defined from statute and regulation.

• Ammo price comparison

  JustAmmo is our sister site that compares delivered ammo prices per round.

  Sister site, same owner as AR15.us. No commission.

• Sources & editorial policy

  How we choose sources, label who published them, and correct mistakes.