The information on the Federal Ammo Ballistics Chart includes index number, gauge, shell length, powder dram equivalent and velocity feet per second at 3 feet, as well as ounces of shot and shot size. The charts are normally used to determine which type of ammunition is best suited for a given caliber and gun style for optimum accuracy and safety.
The ammunition chosen affects bullet trajectory and speed. The index number is used as a type of serial number for the ammunition, and the gauge is the unit of measurement for the bore diameter, the diameter of the barrel of the gun. A higher gauge number means a smaller internal diameter of the barrel.
The shell length is the length of the long side of a single shell. The longer the shell length, the more shot pellets and powder a gun can contain. Ammunition manufacturers use the powder dram equivalent to indicate how much powder a load has. The higher the dram equivalent number, the more energy the ammunition has and the faster the shot will travel.
Because ammunition manufacturers often add new rounds throughout the year, buyers need to regularly check with their ammunition suppliers to make sure they have the best ammunition that is currently available for their guns.