What type of shotgun measurement is defined as .410?

The designation of .410 refers to a gauge of a shotgun, specifically indicating the bore diameter. In the context of shotguns, gauges are a way to measure the size of the shotgun's bore, with a smaller number indicating a larger bore. The .410 gauge is unique because it is named based on the size of a solid round lead ball that would weigh approximately 410 grains. This makes .410 a distinctive classification, as it is actually measured inversely; fewer balls can fit into a given volume compared to those that fit a designation like 12 gauge, which denotes a larger bore size. Understanding this is essential for proper identification and selection of ammunition for shotguns.

Other options do not accurately describe what .410 signifies. For example, caliber typically refers to the diameter of the projectile in rifles or handguns, while choke type and shell length are specific to the characteristics and configuration of shotguns, but they do not relate to the gauge designation.