setback force

setback force

[′set‚bak ‚fȯrs]
(mechanics)
The rearward force of inertia which is created by the forward acceleration of a projectile or missile during its launching phase; the forces are directly proportional to the acceleration and mass of the parts being accelerated.
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References in periodicals archive ?
As the crimp develops, the pellets are forced back by normal setback forces, and the center of the plastic wad starts to bulge.
This theory is based upon pellet deformation: with a high chamber pressure and exit velocity, the lead shot in 3-1/4 drams equivalent loads tend to be mashed in the chamber and bore by both the setback forces of firing and the squeezing and jamming of payload passage through the narrow points of a barrel (like the forcing cone and choke).
The lower-velocity loads, on the other hand, may not deform as many pellets via setback forces, and the gas level at the muzzle will be lower to let the shot charge escape without taking a rap on the fanny from gas-pushed wads.