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The Ultimate Reloading Manual
Wolfe Publishing Group
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  • alliant reloading data
  • reloading brass
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The Ultimate Reloading Manual
hornady superperformance

How Smokeless Burns

Author: John Barsness / Wolfe Publishing Co.
Date: Dec 13 2004

One of the most frequently encountered misconceptions in handloading is that a charge of smokeless powder is still burning when the bullet (or shot charge) exits the muzzle. As “evidence,” many shooters cite the muzzle flash, especially visible in dim light. Nope, that ain’t burning powder. Instead, it’s the hot gas produced by burned powder, re-igniting once it strikes the oxygen in the atmosphere.

Instead, almost all smokeless powder burns within a short distance in front of the cartridge. The exact point varies with the powder’s burning rate, the cartridge, the projectile, etc. But even in huge “magnum” rifle cartridge, over 99% of the powder is burned within 4-5 inches of bullet travel.

If it wasn’t, we wouldn’t call smokeless “smokeless.” The big puff of white smoke produced by black powder is underburned solids. About half of black powder doesn’t burn, not only puffing out smoke but leaving a thick coating inside the barrel. Smokeless powder, under most circumstances, produces neither.

Some smokeless powders do a leave a slight residue inside the barrel that can build up over dozens of shots. This isn’t actually an unburned powder, but (particularly in Ball powders) a coating designed to slow down ignition. Some modern Ball powders almost eliminate this fouling entirely, but some older Ball powders do leave a thin coating of black inside the bore.

Also, under certain circumstances, unburned smokeless powder granules can be blown out the muzzle. Various powders are designed to burn most efficiently at various pressures. Most shotgun powders are designed to burn at about 7,000 to 14,000 pounds per square inch (psi), handgun powders at 12,000 to 35,000 psi, and rifle powders at 35,000 to 65,000 psi.

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