[Pathfinder76]

“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 burned within 4-5 inches
of bullet travel.“

John Barsness