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Black powder granulations

FWAdditFWAddit Member Posts: 918 ✭✭✭✭
edited January 2012 in Ask the Experts
The standard recommendations for loading black powder puzzle me.

The finest granulation, FFFFG, ignites easiest and burns fastest. It's recommended for priming the pans of flintlocks. This makes sense.

The next finest, FFFG, is almost as fast; in fact, Lyman (45th ed.) says it can be substituted for 4F in flintlock pans. It is recommended in pistols. This also makes sense; pistol cartridges normally require fast smokeless powders, so we would expect the same of black. Lyman says it is usually chosen for long guns up to 40 caliber.

The workhorse granulation, FFG, is "for rifles over 40 caliber and up to 58 caliber. Also used in the larger caliber single shot pistols and most shotguns."

In this recommendation, the sequence from fast to slow for black does not correspond to that for smokeless. Straight-cased rifle cartridges such as .38-55 and .45-70 generally require slower smokeless formulations than 40- or 45-caliber pistols, so the Lyman recommendation makes sense here. Shotguns, though, often use the same fast smokeless powders as pistols: Red Dot, 700X, SR4756, and so on. Why, with black, should shotguns use the same slower granulation as rifles?

Okay, I admit I'm no ballistics engineer. In my ignorance, I would expect that barrel length, more than bore diameter, should be what determines the choice of black powder granulation. FFFG for short barrels, so that as much as possible gets burned before the projectile leaves the barrel; FFG for long barrels, so that the slower powder pushes on the payload as long as practicable. In that case, though, a 12 gauge barrel 28 inches long is effectively shorter (because of its expansion ratio) than a 28-inch 45 caliber barrel.

Can someone enlighten me?

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    perry shooterperry shooter Member Posts: 17,390
    edited November -1
    Black powder burns at a constant rate with very little gain with higher pressure. While Smokeless Powder is Progressive the higher the pressure the faster the burn. You start the burn with smokeless and as the pressure the burn rate gets faster and faster.
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    v35v35 Member Posts: 12,710 ✭✭✭
    edited November -1
    I have some Dupont FG that seems to be too slow for anything.
    Black powder can be carefully ground to fine powder between wood only. No metal, plastic or ceramic should be used. 5-10 grain batches seem safe. Keep the operation away from any open or loose powder.
    Priming the touch hole, pan plus a little in the barrel with the fine powder will significantly reduce ignition time over FFFFG.
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    jonkjonk Member Posts: 10,121
    edited November -1
    To say one granulation of black powder burns faster than another is a bit of a misnomer. It all burns at about the same speed. Due to greater surface area vs. volume of each granule, it IGNITES faster in smaller granulations, and burns 'faster' only because each granule is smaller, just like a toothpick burns faster than a log- while the pine wood burns at a roughly constant speed all things considered.

    Smokeless burns faster or slower due to chemical composition.

    Smaller bores mean that the powder is stacked on top of itself more than in larger bores, meaning that the flame 'chokes' with larger granules, but can spread easier in larger bores. Picture wetting a flat piece of newspaper vs. one wadded up and you see what I mean. The paper absorbs water at a constant rate, but it takes longer to wet the wadded up piece.

    That said, despite Lyman's general rule of thumb, a lot of people find 3FG works best in guns up to .45 caliber and even beyond- I use it in my .58 musket even. While 60 gr of FFG would be normal, I use 55 gr of FFFG.
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    MIKE WISKEYMIKE WISKEY Member, Moderator Posts: 9,988 ******
    edited November -1
    "I have some Dupont FG that seems to be too slow for anything.".............you just need a bigger gun [:D], a 3" bore should be about right
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    hillbillehillbille Member Posts: 14,216 ✭✭✭✭
    edited November -1
    I use FFF in all my muzzleloaders, pistol, rifle shotgun and in flintlock barrell and flash pan, I just back the load down 10-15 grains in the rifle, it keeps me from having to keep different horns for each weapon.
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    rsnyder55rsnyder55 Member Posts: 2,526 ✭✭✭
    edited November -1
    Isn't FG for cannon?
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