An adjustable buttstock for a firearm, the buttstock comprising: a longitudinal axis; an elongated stock mounting extension member configured to mount to the firearm; a clamping member disposed on the mounting extension member, the clamping member having downwardly extending and opposing first and second jaws (61, 60); a butt pad assembly comprising an elongated butt pad and a first adjustment rail protruding axially forward from the butt pad, the first adjustment rail received between the jaws (61, 60) and slidable between a plurality of indexed axial positions for adjusting the length of the buttstock; the jaws (61, 60) of the clamping member laterally movable together and apart between a locked position lockingly engaging the first adjustment rail in one of the axial positions and an unlocked position partially disengaging the first adjustment rail which allows the rail to slide axially relative to the jaws between the axial positions; an opening spring biasing the jaws (61, 60) apart; a double-acting cam lever assembly mechanically coupled to the first and second jaws (61, 60), the cam lever assembly comprising a cam lever pivotably mounted on the first jaw and including two opposing locking surfaces (110a, 110b) selectively rotatable into engagement with a bearing surface on the first jaw and a non-locking release surface disposed therebetween; the cam lever pivotably movable from a center release position to one of two opposing locking positions; wherein placing the cam lever in the center release position positions the release surface towards the bearing surface on the first jaw and moves the jaws (61, 60) apart to the unlocked position for adjusting the length of the buttstock; wherein moving the cam lever from the center release position to either of the two locking positions engages one of the locking surfaces (110a or 110b) with the bearing surface on the first jaw and draws the jaws (61, 60) together to the locked position for fixing the length of the buttstock; wherein the locking surfaces (110a, 110b) are arcuately shaped and the release surface is flat. a longitudinal axis; an elongated stock mounting extension member configured to mount to the firearm; a clamping member disposed on the mounting extension member, the clamping member having downwardly extending and opposing first and second jaws (61, 60); a butt pad assembly comprising an elongated butt pad and a first adjustment rail protruding axially forward from the butt pad, the first adjustment rail received between the jaws (61, 60) and slidable between a plurality of indexed axial positions for adjusting the length of the buttstock; the jaws (61, 60) of the clamping member laterally movable together and apart between a locked position lockingly engaging the first adjustment rail in one of the axial positions and an unlocked position partially disengaging the first adjustment rail which allows the rail to slide axially relative to the jaws between the axial positions; an opening spring biasing the jaws (61, 60) apart; a double-acting cam lever assembly mechanically coupled to the first and second jaws (61, 60), the cam lever assembly comprising a cam lever pivotably mounted on the first jaw and including two opposing locking surfaces (110a, 110b) selectively rotatable into engagement with a bearing surface on the first jaw and a non-locking release surface disposed therebetween; the cam lever pivotably movable from a center release position to one of two opposing locking positions; wherein placing the cam lever in the center release position positions the release surface towards the bearing surface on the first jaw and moves the jaws (61, 60) apart to the unlocked position for adjusting the length of the buttstock; wherein moving the cam lever from the center release position to either of the two locking positions engages one of the locking surfaces (110a or 110b) with the bearing surface on the first jaw and draws the jaws (61, 60) together to the locked position for fixing the length of the buttstock; wherein the locking surfaces (110a, 110b) are arcuately shaped and the release surface is flat.