"Normal" A.H. Fox Gun Co. and early Savage-era 20-gauge chambers were about 2 3/8 inch, intended for the "standard" 2 1/2 inch 20-gauge shells of the day. A.H. Fox Gun Co. would chamber new guns for the longer 2 3/4, 2 7/8 and 3-inch 20-gauge shells on request at no additional charge. Like Parker Bros., the A.H. Fox Gun Co. chambered about 1/8 inch shorter than the intended shell length. The belief was that 1/8 inch of the case mouth unfolding into the forcing cone upon firing created a better gas seal and better patterns.
From the late 1890s into the early 1920s, the heaviest smokeless powder 20-gauge loads offered by our North American ammunition manufacturers were 2 1/4 drams of bulk smokeless powder or 18 grains of dense smokeless powder such as Infallible or Ballistite pushing 7/8 ounce of shot.
In the 2 3/4 inch and longer shells one could get 2 1/2 drams of bulk smokeless powder or 20-grains of dense smokeless powder such as Infallible or Ballistite pushing that same 7/8 ounce of shot a bit faster. The 2 7/8 and 3-inch shells just offered more and better wadding which many serious shooters believed in.
In 1922, Western Cartridge Co. brought progressive burning smokeless powder, higher velocity and a heavier payload to 20-gauge shells when they introduced their Super-X load put up in their 2 3/4 inch FIELD shell --
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