The fact that your gun chambers a modern 2 3/4 shell dose not mean it is safe to shoot modern 2 3/4 smokles shells; to do so is to court disaster!The breech pressure developed by most modern smokless, 2 3/4 shot gun shells, is in many cases equal to,or greater,than the proof pressures generated by the original black powder proof test. Prior to shooting smokless loads in any black powder gun it should first be submitted for nitro reproof.
For the record, at the time when your gun was made a 2 1/2 inch and 2 3/4 inch black powder shell with rolled turnover, did, believe it or not, measure 2.5 and 2.75 inches in length! From this you should be able to appreciate the fact that if you tried to chamber a 2.75 B.P. shells in your gun you would not be able to close the action!
Strongly recommend that you abandon the "fishing trip" and send your gun to a competent gunsmith who is properly equipped to acurately measure and evaluate the condition your gun.
