Although there are various designs, with an arrangement of holes and slots of various geometrical shapes, some designs prove to be very effective whilst others are less so. The energy released as the projectile exits the rifle barrel travels adjacent to the direction of the projectile. This energy is then directed through the various geometrically-designed cavities and drives against the exposed faces of the MB (surface friction) which results in a percentage of recoil reduction.
The greater the surface area of these cavities machined at the correct angles, the more effective the MB. The result is greater recoil reduction with a dramatic increase in the Sound Pressure Level (SPL).
MB’s with an array of small holes arranged longitudinally (whether in a helical, staggered or straight formation) can create a reverse effect derived from particle compression, which creates less surface friction to that of the MB. As a result, recoil reduction is not effective and the SPL is not too different from that generated by a standard firearm without an MB.
With the use of an effective MB, the SPL can reach as high as 20dB. This may not seem much of an increase, but taking into account that for every 3dB increase there is a doubling of sound pressure, the exponential result is nearly 7x the increase of the SPL.
This is the main reason why MB’s are discouraged at shooting ranges.
Recoil reduction can be very effective with the use of a correctly-designed MB. However, there are important consequences that a well-designed MB cannot mitigate, even with using ear muffs or ear plugs.
1: Concussion: From the released pressure wave, affecting spotters, other range shooters, hunting dogs etc.
2: Dust signature: Created as the released energy comes into contact with surrounding terrain such as sand or dust.
3: Increased SPL: Affecting neighbouring properties in close proximity to shooting ranges, horses, farm animals, dogs etc.
4: Shooters Flinching: From anticipation of the shot, resulting in missed targets, lost or wounded game.
Sound moderators/ suppressors work in exactly the same way but with the obvious sound reduction features. A moderator / suppressor that has very good sound reduction will generally have good recoil reduction as well.