A self-adjusting clamping system top capture and hold a recoil lug extending outwardly from a bolt style receiver of a firearm. At least a lower portion of the receiver and the recoil lug are received into a chassis having a recess. The chassis is configured to receive an anvil block confronting the rear surface of the recoil lug. The chassis is configured to receive a tightening system confronting the front surface of the recoil lug. The anvil block has a front surface that contacts and confronts the rear surface of the recoil lug. The anvil block also has a rear surface that is outwardly rounded. The tightening system is at least partially wedge-shaped having a front surface that is angled and a rear surface that contacts and closely confronts the front surface of the recoil lug.