Well. The " F " designation is how Black Powder granulation size is Marked on the cans of powder we buy.
Fg( "g" stands for Graphite coated) is considered Coarse Cannon Powder. Its also used in the firework's industry for the aerial fireworks- NOT FIRE CRACKERS! The size of Fg powder is determined by the Size Mesh used in Screens to sort the powder from finer sizes of granules. Fg must pass through a 10 mesh-to-the-inch( 2.54 centimeters) screen, but must NOT pass through a 14 mesh screen.
FFg powder is recommended for use in shotguns, and large caliber rifles( .50 and above)FFg powder must pass through 16 mesh screens, but NOT through 24 mesh screens.
FFFg powder is recommended for small bore rifles and revolvers or pistols. However, we find some LARGE CALIBER rifles and shotguns shoot FFFg powder better than they shoot FFg powder. FOR THAT REASON, we recommend that shooters try both powders in their guns, and let the gun tell the shooter which powder it likes the best. FFFg powder must pass through 24 mesh screens, but not through 46 mesh screens.
FFFFg powder( sometimes just FFFF powder, indicating it has not been coated with graphite)Is Priming powder ONLY. It should ONLY be used to prime flintlock pans, and should never be used as a main powder charge behind a projectile in the barrel. When a gun is loaded without a powder charge under the ball( "Dry-balling") we often can ONLY use 4Fg powder, put down into the flash channel after removing the nipple, or behind the ball in a flintlock,
to shoot the ball out the barrel. Rarely is more than 5 grains by volume of this powder fit behind the ball for this purpose. But, because of its very fast burning rate, it generates lots of gas, VERY FAST( meaning it also raised chamber pressures fast) and is able to push even a heavy ball out the barrel with enough force for the ball to be dangerous for some distance. FFFFg powder must pass through a 46 mesh screen, but not pass thru a 60 mesh screen.
Beyond that, there are 5,6, and at least 7Fg powders made for more limited purposes, that should never be used IN a gun. 7Fg powder is used in fuses, and in some small firecrackers. When old daguerreo-type photography was done in the 19th century, This fine flash powder was used by the photographer to provide the "Flash" needed to imprint the image of the subject being photographed on the chemically treated glass plates in his camera. As soon as the Electric light bulb was perfected, and " flash Bulbs" became available, the use of dangerous flash powder slowly ended. But, these old camera and "flash trays" were still being used by photographers will into the 20th century.
I don't know how you go about finding out the granular sizing of the black powder you are using. My suggestion is to buy some screen of the appropriate size and screen a container of the powder you buy. McMaster-Carr is an American source for screens. (www.mcmaster.com) I suspect there are some European sources you can use. They will be sold in metric sizing,so you will need to do the math.
Here is the opening width of the mesh, in thousandths of an INCH, per my notes when I searched Mcmasters a couple of years ago:
14 mesh= .051" opening width
24 mesh= .028" " "
40 mesh= .015" " "
50 mesh= .015" " "
Opening width is obviously the area through which a particular sized granule of powder must pass using that mesh screening.
I could not find any mesh that was 60 mesh per inch or smaller from McMaster. However, Anything small than 40 mesh meets the test to be called Priming powder ONLY. Anything less than 50 or 60 mesh would be dust. It won't hurt your gun if its ONLY USED in the flash pan of your flintlock.
The only caveat I can give regarding using these fine dusts for flash powder is that they tend to absorb moisture from the air, and any BP residue left in the pan from the last firing, much quicker than do the coarser( larger) granule sized powders. I do not recommend using FFFFg powder, much less finer powders, in your flash pan on rainy days, unless your gun is sheltered, and you expect to fire it quickly.
I hope this helps. :thumbsup: