The 10-foot, 100-pound weapon was so deadly to North America’s waterfowl that it was outlawed by 1918, as just a single shot from the one-gauge gun could kill 50 to 90 ducks — or an entire flock.

The gauge of a shotgun goes down as the caliber goes up. For instance, the standard 12-gauge is equal to a 0.72-inch caliber, but is a small fry compared to the giant 2-gauge punt guns used in the ...