If you've spent any time at the range or scrolling firearm forums lately, you've probably noticed pistol-caliber carbines (PCCs) — and AR-9s in particular — showing up everywhere. What used to be a niche category is now one of the fastest-growing segments in the shooting sports world. Whether you're a competitive shooter, a home-defense enthusiast, or someone who just wants a fun, low-recoil range gun, understanding what AR-9s and PCCs bring to the table can help you decide if one be …