What factors contribute to the weight increase in 3.5-inch shells?

Increased Projectile Length

The primary contributor to the weight increase in 3.5-inch shells is the longer projectile length. On average, the 3.5-inch projectile is 0.5 inches longer than its 3-inch counterpart. This increased length requires more material to maintain structural integrity, resulting in a heavier projectile. For example, a 3-inch projectile may weigh 1.2 pounds, while a 3.5-inch projectile may weigh 1.5 pounds, an increase of 0.3 pounds.

Increased Propellant Charge

To achieve the same muzzle velocity, the 3.5-inch shell requires a more substantial propellant charge. This increased charge adds weight to the shell, contributing to the overall weight gain. In general, the propellant charge for a 3.5-inch shell is 10-15% larger than that of a 3-inch shell. For instance, a 3-inch shell may use 12 grams of propellant, while a 3.5-inch shell may use 13-14 grams, a difference of 1-2 grams.

Shroud and Gas Check Design

The shroud and gas check design also play a role in the weight increase of 3.5-inch shells. The longer length of the 3.5-inch shell requires a more substantial shroud to maintain proper gas flow and prevent gas blow-by. Additionally, the gas check must be redesigned to accommodate the increased length and velocity of the 3.5-inch projectile. These design changes contribute to the overall weight increase of the 3.5-inch shell.