For pure explosive damage, high burn rates or detonation speeds (and accompanying brisance) are generally preferable, but in guns and especially cannons, slower-burning powder decreases firing stresses.
[1] Large-grained powder, made in the traditional way as flat sheets but screened to larger sizes, was introduced in the 1850s by U.S. Army Major Thomas Rodman for his large-calibre cannon.
In 1875 Lammot du Pont invented Hexagonal powder for large artillery, which was pressed using shaped plates with a small center core; about 1.5 inches (38 mm) diameter, like a wagon wheel nut, the center hole widened as the grain burned.
[3] In 1882 the German Rottweil Company developed Prismatic Brown Powder (PBC), which was also adopted by the Royal Navy in 1884.
It retarded burning even further by using only 2 percent sulfur and using charcoal made from rye straw that had not been completely charred.