When a shot is fired from a a gun the gun gets revoked why?

I think you're mistaking "revoke" for "recoil". In the case of firearms, recoil is the Word that describes the rebounding force that the shooter feels after firing a gun. A cartridge is an unfired bullet plus a small amount of explosive material (ie: gunpowder) which are held together by an outer casing. When a gun is fired, a metal part called the hammer strikes the back end of the cartridge that is loaded in the chamber, igniting the gunpowder and creating a contained explosion inside the gun. The bullet seperates from its casing and is forced down and out of the barrel of the gun by the explosion, and the recoil the shooter feels is the force of the explosion, which is trapped inside the gun and escapes by pushing the bullet out of the only opening it can fit through. The force pushing the bullet and explosion out of the gun also pushes back in the opposite direction towards the shooter (aka: recoil). There is always recoil when a gun is fired, but experienced shooters can predict the force of recoil and brace themselves against it, keeping the gun steady in their hands. The larger the amount of gunpowder, the bigger the explosion and recoil caused by it.