You prob already know this, but... Models prior to - iirc, 1927 (or 1928?) - will have 2 9/16" chambers, not 2 3/4" chambers. I had a 1926 model and it had the short chambers.
Also, another trivia note. The black Remington game loads/hulls (rabbit/dove on the box), while they SAY 2 3/4", they are really 2 9/16" hulls!
Good luck!