They take up recoil in two ways. Additional weight is one, and also the fluid movement of the mercury in it.
They are made in different sizes and weights if younare trying to balance things out. Most of them will make the gun butt heavy. Repeaters have the ability of the reducer being put up front in the mag tube. Or even some are made to attach to or to replace the magazine cap.
A lot of competitive ahooters will add these up front and in back. They like very heavy guns to take up the recoil of the many rounds they will ahoot in a day.
