Do you care about realism? Would you like to increase the life of the gearbox? Does your rifle have such high rate of fire that you are not able to make a single shot? Active brake will sort things out.
In SEMI Mode, the brake will not allow for compressing the piston after a shot. The piston will stop in front position which eliminates unnecessary stresses, increasing the service life of Gearbox and its parts. It is very important, especially with an AEG power upgrade.
After releasing the trigger, the rifle immediately stops shooting. Thus, you will gain more realism and, additionally, won’t lose your precious ammunition.