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Old May 9, 2009, 05:44 AM   #1
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Black powder grades

Black powder types are purchased and described by 'grades'. The grades
carry numbers or designations to declare their granule sizes, and their
relative speeds of burning. Those numbers are familiar to pyrotechnicians -
the famous 'F' numbers. Powders come in two broad basic grades, 'a' grade,
or blasting powder, and 'g' grade, or 'sporting' (shooter's) powder.

The more "F"s in a number, the smaller the granule size, and thus, the
faster the powder will burn. So, FFa powder is slower, with a larger
granule size than FFFa, and FFFg is faster than Fg.

The primary difference between 'a' and 'g' grades is processing. Both
powders begin as milled 'meal' powder. The potassium nitrate, charcoal and
sulfur are milled into an extremely fine powder. This milling process takes
many hours and is usually done by remotely operated equipment due to the
inherent danger of the process. The meal powder is consolidated under high
pressure into a 'mill cake' or 'press cake' of solid Black Powder by
hydraulic press. The cake is dried, and crushed into grains. Both types are
then screened to remove fines, and to grade the grain sizes.

Subsequent polishing of the powders may be done in a tumbler. Blasting "a"
type powders are not usually tumbled. If they are tumbled, it is just for a
short time to knock off any sharp an d long projections. Sporting "g" type
powders are tumbled with a tiny amount of graphite to polish the grains.
The base formula is the same. The graphite is not part of the basic Black
Powder formula.

The graphite does act as a burn rate modifier, slowing the burn rate
slightly. But primarily, the graphite serves as a surface lubricant to
make the powder flow more easily when loading guns. It also serves the
cosmetic purpose of making the powder shiny and pretty. The grain sizes
are different for sporting and blasting Black Powder.

Note, as shown in the tables below, that it is conventional to express 'g'
type powder types with multiple 'F's followed by a lower-case 'g', while
'a' grade powders wear a number before one 'F', and a capital "A". So,
"three F g" powder is written as "FFFg", while "three F a" powder is written
as "3FA". This convention is thought to have b een instituted so that less
confusion would exist between powder types.
For a given number of Fs, 'a' grade powder is coarser and slower-burning
than 'g' grades, notwithstanding the graphite polish on the 'g' types.

Sporting Grade Black Powder -- "g" type powders

Powder Grade pass screen, holding, stays on, passing

Whaling 32/64" mesh 3% 4 mesh 12%
Lifesaving 6 mesh 3% 12 mesh 12%
Cannon 6 mesh 3% 12 mesh 12%
Saluting 10 mesh 3% 20 mesh 12%
Fg 12 mesh 3% 16 mesh 12%
FFg 16 mesh 3% 30 mesh 12%
FFFg 20 mesh 3% 50 mesh 12%
FFFFg 40 mesh 3% 100 mesh 12%
FFFFFg (no longer manufactured by Goex)


"A" Blasting Powder
used mostly by pyrotechnicians and for some specialized quarry work

Powder Grade passes screen holding stays on, passing

FA 20/64" mesh 3% 5 mesh 12%
2FA 4 mesh 3% 12 mesh 12%
3FA 10 mesh 3% 16 mesh 12%
4FA 12 mesh 3% 20 mesh 12%
5FA 20 mesh 3% 50 mesh 12%
6FA 30 mesh 3% 50 mesh 12%
7FA 40 mesh 3% 100 mesh 12%
Meal D 40 mesh 3%
Meal F 100 mesh 3%
Meal XF 140 mesh 3%

*** Shows maximum percentages held or passed by the sizing screens.

Commonly used Black Powder Grain Mesh Sizes
FA 3 - 5
2FA 4 - 12
3FA 10 - 16
4FA 12 - 20
5FA 20 - 50
6FA 30 - 50
7FA 40 - 100

Sporting Grades (G) Grain Size (in mm) mm)

Cannon Grade
1FG 1.68-1.19
2FG 1.19-.59
3FG .84-.29
4FG .42-.15
5FG .149

Blasting Grades (A) Grain Size (in mm)
1FA 8.0-4.0
2FA 4.76-1.68
4FA 1.68-.84

5FA .84-.297
7FA .42-.149
Meal D .42
Fine .149

Except where noted in inches, the screen sizes are in wires per inch. The
higher the mesh number the smaller the opening size. Note that, for any
given number of "F"s, that the blasting powder is much coarser.

If you ignore the 'F' numbers, for a given measured grain size, the blasting
powder burns faster than the graphite-inhibited sporting powder; That's
partly because of the inhibiting action of the graphite, and partly because
of the geometry of the grains.

Blasting powder is less dense because the grains are more irregularly
shaped; they take up more volume for a given weight of powder. Blasting
powder grains also have a lot of rough edges. Rough edges both inhibit
packing of grains, and offer lots of easy-to-ignite sites on each grain.
The combination of more air space between grains, and the rougher surfaces
of the grains promotes faster burning.

so, what kind of grade do i use for xx caliber ?

F .50 or greater model cannon; shotguns and rifles over
12 bore (.72 caliber).
FF .36 - .50 large pistols; small rifles
FFF .36 or smaller pistols; derringers
FFFF priming powder for flintlocks.

Sometimes, gunpowder grades are mentioned using P's instead of F's.. So, PP
equeals 2F oand so on..
Summa pia gratia nostra conservando corpora et cutodita, de gente fera Normannica nos libera, quae nostra vastat, Deus, regna.
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