http://armscollectors.com/sn/remdates.php

Puskrat, depends on how old, check the barrel for acase lengthdesignation,cases that are too long will chamber but when fired will not fully open in the 'OLD' shotguns, I have one made in 1908 when the shotgun was called Auto Loader, In 1928 the safety was moved from in front of thetrigger to a lateral cross pin. The Model 11has3friction load adjustment to prevent the bolt from hammering the rear of the receiver,is best to adjust to the heavy setting then change to a lighter settingif the fired cases will not cycle.

You said "OLD Model 11", I do not know if you father purchased it new or used, I would not shoot anything but field loads until I knew more about the shotgun.

F. Guffey