Free recoil
Free recoil is a vernacular term or jargon for recoil energy of a firearm not supported from behind. Free recoil denotes the translational kinetic energy (Et) imparted to the shooter of a small arm when discharged and is expressed in joule (J) and foot-pound force (ft·lbf) for non-SI units of measure. More generally, the term refers to the recoil of a free-standing firearm, in contrast to a firearm securely bolted to or braced by a massive mount or wall.
Free recoil should not be confused with recoil. Free recoil is the given name for the translational kinetic energy transmitted from a small arm to a shooter. Recoil is a name given for conservation of momentum as it generally applies to an everyday event.
Free recoil, sometimes called recoil energy, is a byproduct of the propulsive force from the powder charge held within a firearm chamber (metallic cartridge firearm) or breech (black-powder firearm). The physical event of free recoil occurs when a powder charge is deflagrated within a firearm, resulting in the conversion of chemical energy held within the powder charge into thermodynamic energy. This energy is then transferred to the base of the bullet and to the rear of the cartridge or breech, propelling the firearm rearward into the shooter while the projectile is propelled forward down the barrel, with increasing velocity, to the muzzle. The rearward energy of the firearm can be when calculated is the free recoil and the forward energy of the bullet when calculated and is the muzzle energy.
The concept of free recoil comes from the tolerability of gross recoil energy. Trying to figure the net recoil energy of a firearm (also known as felt recoil) is a futile endeavor. Even if you can calculate the recoil energy loss due to: muzzle brake; recoil operated action or gas operated action; mercury recoil suppression tube; recoil reducing butt pad and or hand grip; shooting vest and or gloves, the human factor is not calculable.
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