At the time this gun was made, our North American ammunition manufacturers were not providing heavier 12-gauge loads in the longer 2 7/8 inch and 3-inch shells than could be had in a 2 3/4 inch shell -- 3 1/2 drams of bulk smokeless powder or 28 grains of dense smokeless powder such as Infallible or Ballistite pushing 1 1/4 ounces of shot.
ARROW 12-gauge 28-grains Ballistite, Remington Arms Co., Inc..jpg
What the longer shells offered was more/better wading.
LEADER 12-gauge 3-inch Special Wadding.jpg
and some of the long shells didn't even have the stoutest loads --
ARROW 12-gauge 2 7-8 inch 01.jpg