If you consider the fact that all the BP granulations are composed of the same mix, they then contain the same energy for a given wt of powder. The granulation controls the rate of burn. A fine granulation gives a higher pressure for a shorter time & vice versa, other things being equal. A "too fine" granulation behind a "too heavy" load could result in a "too rapid" rise in pressure creating a dangerous situation. The burn rate should however relate to load density rather than bore dia. Thus a very heavy load in proportion to bore also requires a slow burn rate. With round ball guns sectional density goes up in proportion to dia so a larger caliber required a slower powder. Shotguns have more commonly been loaded with a similar load density for the various gauges so generally used the same basic granulation, exceptions being sometimes found on both ends, ie extra heavy loads were often used in both the very large bores as well as in the very small ones, but for different reasons of course. Both would then require a coarser granulation than normal.
Last edited by 2-piper; 07/26/07 06:30 PM.
