[citation needed] The momentum delivered to the target, however, cannot be any more than that (due to recoil) on the shooter.
The energy conversion efficiency of a firearm strongly depends on its construction, especially on its caliber and barrel length.
Higher efficiency can be achieved in longer barrel firearms because they have better volume ratio.
However, the efficiency gain is less than corresponding to the volume ratio, because the expansion is not truly adiabatic and burnt gas becomes cold faster because of exchange of heat with the barrel.
Large firearms (such as cannons) achieve smaller barrel-heating loss because they have better volume-to-surface ratio.
According to Newtonian mechanics, if the gun and shooter are at rest initially, the force on the bullet will be equal to that on the gun-shooter.
Were this the case, the shooter would also be thrown backwards, experiencing an even greater change in momentum in the opposite direction.
Gunshot victims frequently fall or collapse when shot; this is less a result of the momentum of the bullet pushing them over, but is primarily caused by physical damage or psychological effects, perhaps combined with being off balance.
This is not the case if the victim is hit by heavier projectiles such as 20 mm cannon shell, where the momentum effects can be enormous; this is why very few such weapons can be fired without being mounted on a weapons platform or involve a recoilless system (e.g. a recoilless rifle).
This is despite ignoring drag forces, which would in reality cause the bullet to lose energy and momentum in flight.