Black Powder Sizes

(This information is for information purposes only. Double check it against other sources. I accept no liability for its use or misuse.)

Black powder is sold by fineness of granule size. There are four commercial sizes distinguished by the letter ‘F’ representing the fineness beginning with a single ‘F’ with each addition letter ‘F’ signifying a smaller granule. The letter ‘G’ is added to the end of the designation to signify the word “granule”. The grades are said to be then single f, double f, triple f, or quadruple f or else said to be one fg, two fg, three fg, or four fg. They are written as, “Fg, FFg, FFFg, FFFFg”.

The four types are used for different purposes in black powder shooting.

Type Purpose
Fg Small Cannon and Large Bores
FFg General Shotgun and Rifle
FFFg Most Pistol
FFFFg Smallest Pistols and Flash Pan Priming Powder

Exchanging FFg and FFFg – FFg and FFFg are similar enough that in most cases they are interchangeable but because FFFg is of a smaller size it is better for revolvers because the cylinder chambers are smaller and do not always allow for a full charge if using the larger granule size of the FFg. However FFg will usually work in such a gun of medium caliber like a .44 army revolver but the powder will not burn as throughly which is not only less efficient but also leaving some smoldering powder raising the risk of chain-fire accidents which are very dangerous (although we must follow a rule help prevent chain-fire accidents by greasing the end of each chamber before firing in any case) and burns on your skin. So if you can purchase both types of powder is best to have both available and to clearly mark your powder horns and measures. If you have a variety of weapons and must choose only one powder to buy I think FFg is the best choice as it is more generally useful and can be crushed a bit more to make something like FFFg; however that is something you would only want to do as an emergency expedience as the size would not be uniform and could burn faster than you expected. So to prevent this if such an effort must be undertaken the powder should be screened to only select granules of correct FFFg size and the finer powder discarded or used as priming powder for flash pans.

However when using FFFg in a rifle or shotgun it is a good safety measure to lower the charge by about 10-15%. Some people load their shotguns with FFFg exclusively, but I think FFG is more suitable as it will burn more evenly, reduce pressure, is safer, and fills a shotgun cartridge more appropriately when using 1/2 inch fiber wads.

Additional FFFFg information – FFFFg can be used in very small caliber black powder pistols like .22 caliber or even in .22 caliber cartridges, but it is unsafe in medium caliber pistols and rifles and shotguns. It simply burns too fast for those purposes. Also it is good to know that FFFFg is usually used for the flash pans of flintlock guns and so its ingredient ratio may a bit different having more sulfur making it easier to ignite.

Powder Charges – You should always follow the charge tables given to you by your firearm manufacturer and before firing a gun have a qualified gunsmith inspect the gun to ensure it is safe to fire.

GOEX powder company has good charts for general use http://www.goexpowder.com/load-chart.html

At the website http://www.blackpowderrifleaccuracy.com/powder.html a general guide for estimating an appropriate charge for rifles is given which says:

“Large bore rifles (typically larger than .62 caliber) will use larger charges of Fg. Medium bore rifles of between .45 and .62 caliber will use moderate charges of FFg. Smaller rifles and most pistols will use relatively light charges of FFFg. Specific charges are not given here, because that is what you determine while working toward a good group. A very good starting point for determining what charge size to use is to use 1.5 grains of powder per point of caliber for Fg and FFg loads. It is safer to begin FFFg loads at 1 grain per point of caliber. Here are a couple of examples:

  • You have a .32 caliber squirrel rifle, and are usiing FFFg powder. An excellent starting charge would be 30 grains of FFFg.
  • You have a 54 caliber Hawken rifle, and are using FFg powder. A good starting charge would be 75 grains of FFg.
  • You have a .75 caliber Jeager rifle, and are using Fg powder. A good starting charge would be 105 grains of Fg.”

That may work fairly well with long chambered guns like rifles, but 44 grains in a revolver of .44 caliber is more than what manufacturers like GOEX recommend. They usually say to use 30 grains of FFFg and 40 maximum. I have seen published loads where .44 caliber guns are as high as 42 grains of FFFg, but I have always had good success with the standard load of 30 grains. And so remember his advice relates to long guns, not to pistols.

Screening – To sort powder the companies use screen meshes. On page 30 of the Study book number 11 of GunPro Correspondence Course from North American Correspondence Schools contains a chart is shown which is courtesy of Thompson/Center Arms) listed as Table 8. The text says, “To determine granule size, a “Go” and “No Go” system was employed. Powder was passed through a series of screens which contained a given number of meshes per square inch. These screens became progressively finer so that powder was trapped, separated, and graded at various stages in relation to its courseness. BLACK POWDER WAS PASSED THROUGH A SERIES OF SCREENS TO DETERMINE ITS GRANULE SIZE.” The picture depicts powder passing through a wider screen called a “GO” screen and being stopped below by a “NO GO” screen. The sizes listed for the types of powder are…

Type GO (meshes per inch) NO GO (meshes per inch)
FG 10 14
FFG 16 24
FFFG 24 46
FFFFG 46 60

Unfortunately it does not tell us how thick the wires are or what they make them of.

Another source for information about granule size is in the pdf “Black Powder Loading for Cowboy Action Shooting: A Primer” by Joel “Doc” Shapiro SASS #31526 (this is an EXCELLENT guide for black powder shotshells also) https://edoc.site/black-powder-loading-for-cowboy-action-shooting-pdf-free.html

On page 10 a chart is given telling us the actual size of the granules in commercial powder. I reproduce it here.

Granulation Size2 Application
Fg .0689 – .0582 inch 12 ga and larger bores.
FFg .0582 – .0376 inch 44 Caliber to 12 ga.
FFFg .0376 – .0170 inch Calibers smaller than .44
FFFFg .0170 – .0111 inch Priming flash pans

If I understand the numbers given by taking both sources of information together would could estimate the size of the wires used in screening.

For example we know that one mesh may be 16 holes for per inch which is 1/16 = space allowed for each hole with it’s wires on both sides which gives us an area for our figuring of .0625 per unit, then we know within that unit each granule can be at maximum (for FFg) .0582 so we subtract .0582 from .0625 which gives us .0043 and then we divide that into two (since there are two wires in that remaining space) for… .00215. And of course the grains pass somewhat freely through the GO screen so the wires within each space are about two thousandths of an inch; perhaps a little thinner than that, but we have to double this number because a wire is to span the same area in both adjacent spaces so we’re talking around a .004 inch wire. And of course they would need to be finer for each finer screen. But we could run through this procedure each time to estimate the wire thickness a manufacturer may use.

And just for kicks were could theorize that if the powder were produced by an extrusion process using a screen instead of screening the final product which had been broken up again we can estimate the size of the wire by subtracting the smallest granule size a type of powder can be from the largest (say for FFg .0582-.0376 for a medium granule size of FFg of about .0206) and subtracting that from 1/16th on an inch (1/16 = .0625 – = .0418 / 2 = .2095 and then we double that) so that the wire size for such a machine would be 0.419 inches thick laid out in 16 even divisions per inch. So I would figure that a .042 thick wire set up that way for creation by extrusion should theoretically work well for producing something resembling FFg by that sort of process, but the factories use screening to produce their goods probably to allow them to compact the product during drying (the product being something which they can then break apart and screen for size) whereas extrusion would probably separate the ingredients perhaps more than compact them.

But in any case as you could guess the wire used to make mesh then for FFFFg screening would be very fine indeed. Commercially FFFFg is less commonly seen in stores, but not because of the difficulty in making it, but simply because it’s less useful.

But one may not have a particular size wire. What then? By substracting the maximum granule size by minimum granule size you have the difference. Adding that to the minimum size gives the medium size. Then the thickness of the wire can be laid beside that as many times as needed alternating between wire and marked open space or using a precision ground spacer or even a typical granuoe over the distance of about an inch to create an screen size estimation to produce an appropriate screen for extrusion or just by using the minimum and maximum numbers alone to create a set of screening for sift screening. In any case the american standard scientific screening sets commercially available can approximate production screens but not precisely. But it seems production varies a lot in the black powder industry and the numbers given are in fact averages and approximations.

For example in the book Handloading – A publication of the National Rifle Association of America by William C. Davis, Jr. (1981) there is a chart which gives us even more varieties of black powder types than just what is commercially typical and the respective sizes of screens used to sort them. The chart is on page 25 and here I reproduce it:

 

Powder Types        
ARMY NAVY DUPONT SPORTING SCREEN OPENING IN INCHES (PASS) SCREEN OPENING IN INCHES (HOLD)
WHALING .441 .156
A-1 .187 .0937
CANNON .132 .0661
LIFE SAVING .131 .065
Fg .0689 .0582
A-3 .0661 .0469
FFg .0582 .0376
 –  MUSKET .0555 .0280
 FFG  .0469  .0232
A-4 .0469 .0165
SHELL .0469 .0117
FFFg .0376 .0170
FFFG .0331 .0117
FFFFg .0170 .0111
A-5 FUZE .0165 .0059
FFFFG .0138 .0041
MEAL .0098 .029
A-6,-7 .0059 .0041

 

When using that chart know that the commercial DuPont type powders are what is sold to typical users of black powder firearms and so the numbers in the chart for the DuPont kind probably are closer to what you would see on the shelf in a store than the naval kind. Also notice that the powders which are listed by granule size using the convention of the letter “G” conventionally use the lower case “g” for commercial powders and the upper case for naval. Also notice the sizes of the double and triple f types are different for commercial and naval types.

Additional information provided by that book about American consumer type powder is while the approximate ratio of the ingredients of black powder are 75% saltpeter, 15% charcoal, and 10% sulfur in actual commercial production for American consumers the proportions are actually 74%, 15.6%, and 10.4% respectively. (page 23). 

SAFE LOADS – Now as for as what loads are appropriate we can look at GOEX’s chart again to get an idea of how each kind of powder can be used as we must use a chart made for black powder. We can not use conventional smokeless powder charts. To do so would be disastrous and probably deadly. For black powder loaded cartridges we have loads much higher in terms of the powder’s weight in grains being used than we would see in smokeless powder, but the pressures shown by the charts which are good estimates of the kinds of pressures we can expect are much lower.

For instance in the .357 Magnum cartridge GOEX recommends using 25 grains of FFFg over a 160 grain bullet for an estimated velocity of 900 feet per second but smokeless powder guides tells us that only 6.2 grains of a particular powder can achieve 1050 feet per second over a 158 grain bullet and that the load is at the maximum (after which it becomes dangerous to use more powder) at merely 7.2 grains of that smokeless powder.

So we can see that smokeless powder is much more powerful than black powder and loads from guides for one type of powder can NOT be exchanged for another. They are not even close. Even when one type of smokeless powder is compared to another you will see these vast discrepancies of pressure. Pressures generated by smokeless powder is very high and very unforgiving and even deviating from the published guides for black powder loads is extremely dangerous.

The published guides for reloading ammunition then must be followed exactly, not only in terms of how MUCH powder to use but also of what TYPE of powder to use and also careful attention must be paid to bullet WEIGHT.

And although not discussed in this article in detail (I’ll save that for another article) how far back the bullet is seated (which is the principal thing which affects the “cartridge over-all length” abbreviated as C.O.A.L) affects pressure greatly and more sophisticated guides than provided by GOEX will list the COAL you are supposed to use with a particular bullet. And another thing which can affect pressures considerably is the type of primer used.

This all means that we must stick with published data as much as humanly possible in order to be safe. Only genuine and well educated experts of internal ballistics can deviate from published load data.

However having said all that black powder cartridge reloading is more forgiving than using smokeless powder as it is difficult to overcharge the cartridge as black powder has more bulk than smokeless powder and is designed to fill up the cartridge when correctly loaded (and this eliminates the chance for an accidental double charge which is usually possible in smokeless powder reloading) and modern firearms are made to resist pressures higher than a properly loaded cartridge will achieve with black powder. (There are exceptions however and in shotgun reloading there is more of a chance for error than in short cartridges.)

This is NOT true of smokeless powder however. Smokeless powder is NOT designed to fill a cartridge. Filling a cartridge with smokeless powder is almost always dangerous unless the load was specially designed to do so by experts who create load data.

Strangely the inverse is true of black powder as all Loads for Black Powder must be Compressed. And strangely it is CRITICAL to know that an error which can cause immediate pressure problems and catastrophic failure with black powder cartridge reloading is airspace left inside the cartridge.

As I wrote before in smokeless powder a full cartridge is often dangerous unless the the experts recommend such a load with a particular powder and the pressures are regarded by a professionally published guide as being safe. But with black powder the situation is the opposite. Black powder does not burn as efficiently as smokeless powder does and in a black powder loaded cartridge any airspace left within the cartridge causes an air bubble to form which ruptures the case and can perhaps even rupture the chamber of the gun which can result not only in the destruction of the firearm but also the death of the shooter of it. This is why loading charts like the GOEX chart do not give you a selection of reduced pressure loads to try. To do so would be dangerous. The recommended powder charge weights are those expected to fill the case to the proper fullness.

When creating that data black powder loads are designed so that the charge fills the cartridge leaving just enough room for the bullet to be seated in a way that slightly compresses the powder since black powder burns best when slightly compressed and that is the only safe way to fire it anyway. And so if using correct published data correctly there is no chance for a pressure bubble to form inside the case and providing the firearm and cartridge is all in good working order the load should be considered safe. With correct loading procedure and when using correct loading data when firing the bullet will simply move forward as it should relieving the pressure inside the cartridge case and chamber and as the powder continues to burns it should accelerate the bullet using the mathematical curvature expected by the experts and as the bullet travels down the barrel the pressure in the chamber will lower from its peak pressure point which occurs immediately after initial ignition of powder.

And load data for black powder cartridges is designed so as to fill the case just beyond where the base of the bullet is to be seated allows the whole cartridge, chamber, frame, and barrel to support the pressure evenly so that there are no stress points that could cause a rupture.

The recommendation used by the experts when designing their loads is that loads be designed to fill the case to the point the bullet will be seated and about 1/16th or in some cases 1/8th on inch beyond that level so that some compression can be achieved during the reloading stage of seating the bullet.

And so you would think that there is no way to create a reduced pressure load for black powder cartridges. However there is a trick that can be used to produce reduced loads for black powder cartridges.

By separating some of your powder from the rest of your store you can mix some corn meal into it making it more bulky but less powerful. By using a volumetric measure (using perhaps a scooper that throws a known weight of pure powder rather than of adulterated powder) you can still load to the same bulk filling the case as you should but the load will be more mild when firing. Some people also add filler material in the form of paper or fiber wadding which is added on the top of the charge to fill the case a bit more but that is more involved as some types of filler material are appropriate and some is not and because the size and shape and weight of the filler material is very important as too large or too heavy a filler could cause a rupture. So the corn meal trick is the preferred solution.

(Note: this article is incomplete and will be revised and additional information will be included so please be patient as there more to come).