The grain sizes we use now, in the American grain sizing system, were introduced in 1836 as a means of standardizing grain sizes within the industry. They were not used as such until much later in that century.
Capt. Alfred Mordecai, in 1844-45 describes the grain sizing of various powders he tested as "even" or "uneven".
The type of powder, i.e., sporting, rifle or musket denoted differences in ingredient purity standards and differences in basic chemical burn rates.
With black powder they tailored the chemical reaction rates to best suit the type of arm the powder was to be used in.
In cannons you wanted the propelling force to be a large volume of gases at relatively low temperatures. In small-caliber sporting arms the best propelling force was a small volume of gas at a far higher temperature. This being controlled by the proportions of the ingredients and how finely the ingredients were ground during powder processing.
Back about 20 years ago I collected old powder samples and ran screen analysis on them. Comparing that to modern powders. All I did was to confirm and further explain what Mordecai had written.
I should point out that here in the U.S. the production of musket type powders ceased near the end of the Civil War. This left sporting and rifle powders in production. By the opening decade of the 20th century the production of sporting powder ceased, leaving only rifle type black powder in production.
With the Swiss in the U.S. market we now may choose between a rifle type (burn rate) powder (GOEX and Schuetzen)and a true sporting burn rate powder in the form of the Swiss powder.
Generally, a rifle powder was about 10% "stronger" than a musket powder and a sporting powder was at least 10% "stronger" than a rifle type powder.
In Europe, the "best sporting" powders were up to 20% stronger than a rifle burn rate powder.
The terms musket, rifle and sporting pre-date the introduction of uniform grain sizes. When powder was ordered for the Lewis & Clark expedition you see orders for "rifle powder" and "best rifle powder".