The property that determines what kind of ammunition a firearm is designed to use is the:

• A. Cartridge
• B. Caliber
• C. Powder
• D. Primer

Answer: (A)

Cartridge

The cartridge is the complete ammo unit—the case, primer, powder, and bullet—that a firearm is designed to chamber and feed. The gun’s chamber and feeding mechanism are machined to fit a specific cartridge design and length, so compatibility depends on matching that cartridge precisely. Caliber refers to the bore diameter, which is related but doesn’t by itself determine which ammunition the firearm accepts, since cartridges with the same caliber can have different shapes or lengths that require different chambers. Powder and primer are components inside the cartridge, not the overall determinant of what the firearm is designed to use. So the property that sets the ammunition type a firearm is built for is the cartridge.