The Firing Line Forums - View Single Post - fast burning powder or slow burning powder?

Chris McDermott · January 24, 2001, 09:32 PM

Vince

It sounds like you are looking for general principles here for powder selection. It really depends on the relationship between case volume, bullet weight and caliber (diameter of bore). The case volume is the amount of space the powder has to start burning in, the caliber determines how much this space will grow as the bullet starts to move, and the bullet weight (inertia) helps determine how fast the bullet will accelerate.

Cartridges with small case volumes and light bullets (say 32 ACP for an extreme case) have to use very fast burning powder to get pressures built to give the bullet extra speed (velocity depends on pressure). Slow burning powders just wouldn't finish burning til the bullet was out of the barrel. Conversely a big case volume with heavy bullets, say a 460 Weatherby, needs very slow burning powder to let the bullet start moving down the barrel before it all burns up and builds way to much pressure, blowing up the gun. (yes, a case full of a fast pistol powder like Bullseye in most any rifle caliber will chop your rifle in half - in any of the popular actions Mauser 98, Remmington 700, Winchester 70, Ruger MkII etc)

Selecting the proper burn rate for your application is best done by looking in a loading manual.

AA #9, 2400, H110/W296 are very slow pistol powders, but in a rifle case they are really only useable for very light cast bullet loads, and the 22 Hornet (small case, light bullet) as they are just too fast. Conversely I don't think anyone has ever tried using slow rifle powders like H1000 or RL25 in a pistol cartridge; and I wouldn't even try. If the bullet sticks in the barrel it can cause a very sudden pressure rise as the rest of the powder then burns before the bullet can start moving again, producing dangerously high pressures.

For auto-loading actions that are gas operated, using a powder that provides the correct pressure at the gas port to work the action is critical for proper operation. Even for blow-back and recoil operated actions getting too far away from the ammo the gun was designed for will cause the gun to jam or beat itself to death as the amount and speed of recoil changes.
Example : Model 1911's in 45ACP for Bullseye target shooting typically use light 10 lb recoil springs with the light Bullseye target ammo of a 185 grain bullet at 750 fps. Standard guns use 16 lb springs for typical off the shelf ammo of a 230 grain bullet at 850 fps. Target ammo in a standard gun won't work the action and it jams/fails to eject on every shot; standard ammo in a Bullseye gun will beat it to death in short order.

January 24, 2001, 09:32 PM	#6
Chris McDermott Senior Member Join Date: March 30, 2000 Posts: 245	Vince It sounds like you are looking for general principles here for powder selection. It really depends on the relationship between case volume, bullet weight and caliber (diameter of bore). The case volume is the amount of space the powder has to start burning in, the caliber determines how much this space will grow as the bullet starts to move, and the bullet weight (inertia) helps determine how fast the bullet will accelerate. Cartridges with small case volumes and light bullets (say 32 ACP for an extreme case) have to use very fast burning powder to get pressures built to give the bullet extra speed (velocity depends on pressure). Slow burning powders just wouldn't finish burning til the bullet was out of the barrel. Conversely a big case volume with heavy bullets, say a 460 Weatherby, needs very slow burning powder to let the bullet start moving down the barrel before it all burns up and builds way to much pressure, blowing up the gun. (yes, a case full of a fast pistol powder like Bullseye in most any rifle caliber will chop your rifle in half - in any of the popular actions Mauser 98, Remmington 700, Winchester 70, Ruger MkII etc) Selecting the proper burn rate for your application is best done by looking in a loading manual. AA #9, 2400, H110/W296 are very slow pistol powders, but in a rifle case they are really only useable for very light cast bullet loads, and the 22 Hornet (small case, light bullet) as they are just too fast. Conversely I don't think anyone has ever tried using slow rifle powders like H1000 or RL25 in a pistol cartridge; and I wouldn't even try. If the bullet sticks in the barrel it can cause a very sudden pressure rise as the rest of the powder then burns before the bullet can start moving again, producing dangerously high pressures. For auto-loading actions that are gas operated, using a powder that provides the correct pressure at the gas port to work the action is critical for proper operation. Even for blow-back and recoil operated actions getting too far away from the ammo the gun was designed for will cause the gun to jam or beat itself to death as the amount and speed of recoil changes. Example : Model 1911's in 45ACP for Bullseye target shooting typically use light 10 lb recoil springs with the light Bullseye target ammo of a 185 grain bullet at 750 fps. Standard guns use 16 lb springs for typical off the shelf ammo of a 230 grain bullet at 850 fps. Target ammo in a standard gun won't work the action and it jams/fails to eject on every shot; standard ammo in a Bullseye gun will beat it to death in short order.