[Researcher]

The 12-gauge Baker SBT's might have 2 5/8-inch chambers intended for 2 3/4-inch shells, but more likely 2 3/4-inch chambers. For 1907 our ammunition manufacturers went to 1 1/4-ounce 12-gauge loads only being offered in 2 3/4-inch or longer shells. Also, for most of the time from then until WW-II while hunting 1 1/8-ounce 12-gauge loads came in the 2 5/8-inch shell, those marketed as "Trap Loads" came in 2 3/4-inch cases.

FIELD 12-gauge 2 3-4 inch, Trap Load, DuPont Smokeless.png

FIELD 12-gauge, 2 3-4 inch, TRAP LOAD, DuPont MX 1-piece.jpg

TRAP LOAD 12-gauge, 2 3-4-inch, two-piece box.jpg