Courtesy of Breach Bang Clear
Term: Powder Burn
Relates to: Measurements(s) and Adjustments
Applications of Use: Shooting, Reloading, Long Range Precision, “Throat Erosion”, Muzzle Velocity, Interior (often referred to as Internal) Ballistics
Definition: The burning of propellant found in modern firearms relating to a percentage burned in a specific length barrel.
Why it Matters: This term is primarily heard in online arguments over required barrel length. If you frequent any precision rifle board or AR15 board and hang around long enough someone will start an argument about application of a short barrel in X-caliber being just as good as another longer barrel. For any modern cartridge, barrel length has a direct link to muzzle velocity. Longer barrels give the propellant more time to burn and build pressure behind the bullet before it leaves the muzzle. The second the bullet leaves the muzzle the bullet starts slowing down. Bullets fly the most predictably in supersonic flight, so the faster it is when it starts its flight, the longer the distance is before passing into transonic and subsonic flight. This comes down to retained velocity. The more retained velocity over the same period of time or distance, the more efficient. The transition into trans and subsonic flight can cause a bullet to fly erratically because of the rate at which the bullet loses velocity.
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Featured photo courtesy of Forensic Outreach