Specifications
The name derives out of an old English practice of bore measurements in gunmaking, meaning a perfectly round pure lead ball that exactly fits the bore of the weapon would weigh 1/4 lb -- that is, 0.25 lb (0.11 kg) (see gauge). The 4 bore was made to fire roundballs of 1/4 pound lead, or approximately 1750 grains (1750 gr.) and approximately 1-inch (25 mm) calibre (more precisely, 1.053-inch (26.7 mm), when shooting pure lead bullets). This varied greatly as in muzzle loader days shotgun gauges were custom made and often differed from the actual bore measurements. Commonly, 4 gauges were closer to .935-.955 calibre, pertaining to a 1400 gr. alloyed lead ball and closer to 5 gauge.
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