12 Ga Ammo
The 12 Ga shotgun shell is by far the most popular size in the United States, and possibly the entire world. It's a multi-purposed gauge that offers the choice of hunting, and home-defense. It's even the standard gauge used by the Military as well as Law Enforcement agencies. Since 12 Ga ammunition is widely available in different shot types, a shooter armed with an inexpensive 12 Ga shotgun could conceivably hunt all species of game in North America, or protect their home with the change of a barrel, choke, and ammo.