Recoil - Perception of Recoil

Perception of Recoil

For small arms, the way in which the shooter perceives the recoil, or kick, can have a significant impact on the shooter's experience and performance. For example, a gun that is said to "kick like a mule" is going to be approached with trepidation, and the shooter will anticipate the recoil and flinch in anticipation as the shot is released. This leads to the shooter jerking the trigger, rather than pulling it smoothly, and the jerking motion is almost certain to disturb the alignment of the gun and result in a miss.

This perception of recoil is related to the acceleration associated with a particular gun. The actual recoil is associated with the momentum of a gun, the momentum being the product of the mass of the gun times the reverse velocity of the gun. A heavier gun, that is a gun with more mass, will manifest the momentum by exhibiting a lessened acceleration, and, generally, result in a lessened perception of recoil.

One of the common ways of describing the felt recoil of a particular gun-cartridge combination is as "soft" or "sharp" recoiling; soft recoil is recoil spread over a longer period of time, that is at a lower acceleration, and sharp recoil is spread over a shorter period of time, that is with a higher acceleration. With the same gun and two loads with different bullet masses but the same recoil force, the load firing the heavier bullet will have the softer recoil, because the product of mass times acceleration must remain constant, and if mass goes up then acceleration must go down, to keep the product constant.

Keeping the above in mind, you can generally base the relative recoil of firearms by factoring in a number of figures such as bullet weight, powder charge, the weight of the actual firearm etc. The following are base examples calculated through the Handloads.com free online calculator, and bullet and firearm data from respective reloading manuals (of medium/common loads) and manufacturer specs:

• In a Glock 22 frame, using the empty weight of 1.43 lb (0.65 kg), the following was obtained:
  • 9 mm Luger: Recoil Impulse of 0.78 ms; Recoil Velocity of 17.55 ft/s (5.3 m/s); Recoil Energy of 6.84 ft·lbf (9.3 J)
  • .357 SIG: Recoil Impulse of 1.06 ms; Recoil velocity of 23.78 ft/s (7.2 m/s); Recoil Energy of 12.56 ft·lbf (17.0 J)
  • .40 S&W: Recoil impulse of 0.88 ms; Recoil velocity of 19.73 ft/s (6.0 m/s); Recoil Energy of 8.64 ft·lbf (11.7 J)
• In a Smith and Wesson .44 Magnum with 7.5-inch barrel, with an empty weight of 3.125 lb (1.417 kg), the following was obtained:
  • .44 Remington Magnum: Recoil impulse of 1.91 ms; Recoil velocity of 19.69 ft/s (6.0 m/s); Recoil Energy of 18.81 ft·lbf (25.5 J)
• In a Smith and Wesson 460 7.5-inch barrel, with an empty weight of 3.5 lb (1.6 kg), the following was obtained:
  • .460 S&W Magnum: Recoil Impulse of 3.14 ms; Recoil Velocity of 28.91 ft/s (8.8 m/s); Recoil Energy of 45.43 ft·lbf (61.6 J)
• In a Smith and Wesson 500 4.5-inch barrel, with an empty weight of 3.5 lb (1.6 kg), the following was obtained:
  • .500 S&W Magnum: Recoil Impulse of 3.76 ms; Recoil Velocity of 34.63 ft/s (10.6 m/s); Recoil Energy of 65.17 ft·lbf (88.4 J)

In addition to the overall mass of the gun, reciprocating parts of the gun will affect how the shooter perceives recoil. While these parts are not part of the ejecta, and do not alter the overall momentum of the system, they do involve moving masses during the operation of firing. For example, gas-operated shotguns are widely held to have a "softer" recoil than fixed breech or recoil-operated guns. In a gas-operated gun, the bolt is accelerated rearwards by propellant gases during firing, which results in a forward force on the body of the gun. This is countered by a rearward force as the bolt reaches the limit of travel and moves forwards, resulting in a zero sum, but to the shooter, the recoil has been spread out over a longer period of time, resulting in the "softer" feel.