Why recoil of gun is much smaller than velocity?

Answer: It is due to the law of conservation of momentum. The total momentum of the gun and bullet after firing is equal to the total momentum of the gun and bullet before firing. Mathematically MV = -mv. The negative sign indicates that the direction of recoil is opposite to the velocity of bullet. Since, the mass of gun is much larger so the velocity of recoil is much smaller as compare to the velocity of bullet.