..............(parts)..................Saltpeter.....Charcoal........Sulfur
Marcus Graecus (ca. 1250)........100.............33...............12
Canton of Zurich (1775)............100...........16.7.............16.7
Swiss Army (1849)...................100...........17.3..............16.0
Modern Swiss blackpowder........100............20.0.............13.3
Ulrich Bretscher's Black Powder Page
There has been no significant change in the formulation of black powder through the centuries. I would not attribute modern day fouling to differences in the powder made today. Remember that quality control in the 17th, 18th, and 19th centuries was far from ideal, so every can of powder purchased was probably different. The types of wood used, the degree of heat supplied to make charcoal, and the size and uniformity of particles are all big factors in consistent manufacture of black powder and only the technologies of today are able to make uniform quality product. I also think that using tallow, whale fat, lard, etc. when loading will provide dramatically different and improved effects when compared to modern concoctions like Crisco, petroleum products, etc., which will add to fouling in modern BP revolvers.
My belief is that the load also plays an important part in how clean or “dirty” your revolver gets. I shoot percussion and flintlock guns and have learned over the years how to eliminate hard fouling in the barrels. After shooting a few rounds, a ring of hard carbon will form somewhere in the barrel that makes reloading difficult. If you increase the load of BP, you can push the carbon ring that forms further down the barrel, until the point where it will form beyond the muzzle. Once that load is determined, I can shoot dozens of rounds without needing to clean the gun. I suspect that the loads or BP particle size can be modified to have a similar positive affect in percussion revolvers.
Bottom line is that the guns of old suffered the same problems as modern reproductions and needed constant cleaning to keep working, but if that was your only weapon of defense and food, you would have plenty of time to figure out how to maximize its usefulness by changing powder, load, particle size, and lube. Today, most people are occasional shooters and do not spend the time to perfect their loads.
I am also sure that some manufacturers provide reproductions that may be a little tight, but most are true to the tolerances of old. Maybe corrosion and erosion was a friend of the old time shooters who shot so many rounds that the guns actually worked better as they got more worn. How many times do you see a BP revolver for sale at Gun Shows and they all look brand new!!!! We clean and oil our guns to the point that they don’t even lose their finish after lots of BP is shot. I seem to recall that S&W early cartridge revolvers were built so tight that they always lost government tests when compared to Colt. S&Ws fouled quickly and Colt revolvers continued to produce more shots before fouling, which was apparently an important criteria for the government testers, and for good reason.