Abstract: A booster system including a piston housing, a piston, a spring, and a rear cap attached to the piston housing. The piston housing includes an annular outer wall and an annular projection extending inward from the outer wall at a rear end of the piston housing. The piston is disposed within the piston housing and includes a bore and a radially outwardly extending flange at its front end. The spring is radially disposed between the piston housing and the piston in a space enclosed by the outwardly extending flange and the annular projection. The rear cap includes an end wall extending radially outward from a rear end of the piston housing. A side wall extends forward from the end wall and hangs over the outer wall of the piston housing at a radial distance from the outer wall of the piston housing. The sidewall of the rear cap includes an engagement surface for attachment to a body of a silencer.