A user-adjustable recoil reduction system for a firearm includes a buttstock and a butt pad assembly movably mounted to the buttstock. A spring is disposed in the buttstock which is acted on by opposing front and rear spring guides. A preload adjustment screw is rotatably coupled to the butt pad assembly which engages the rear spring guide. Rotating the screw in opposing directions alternatingly advances or retracts the rear spring guide in the buttstock. Advancing the rear spring guide compresses the spring to set a first spring preload condition and retracting the rear spring guide relaxes the spring to set a second spring preload condition different than the first condition. The spring preload conditions may be selected to match firing light or heavy type ammunition shell loads. In one embodiment, the adjustment screw is accessible for adjusting the preload without removing the butt pad assembly from the buttstock.