The AR-9, an AR-style 9mm pistol caliber carbine (PCC), is a popular home defense choice. It offers mild recoil, easy handling in tight hallways, and magazine compatibility with many 9mm handguns. But configuration matters as much as the platform. This guide covers the key decisions, from barrel length to storage and training. Disclaimer: This article is for general education, not legal advice. Firearm laws vary by location and are changing quickly. The legal information here reflects ATF guid …