No one can tell you over the internet what ammunition may or may not be suitable for a given gun. That can only be done by a qualified double gun smith (not Joe S**t the 870 parts replacer down at the corner) with the gun in hand.
FOX CHAMBERS --
The only two A.H. Fox Gun Co. catalogues, that I have seen, that state chamber lengths are the 1913 and 1914. They both state 12-gauge guns are regularly chambered for 2 3/4 - inch shells, 16-gauge 2 9/16 – inch shells and 20-gauge 2 1/2 - inch shells. That being said, virtually every 12-gauge Ansley H. Fox gun made in Philadelphia (other than the HE-Grade Super-Fox) that I've run a chamber gauge in shows about 2 5/8 - inch. The chambers of unmolested 16-gauge guns seem to run about 2 7/16 inch and 20-gauge guns a hair over 2 3/8 inch. A very few graded guns were ordered with longer chambers. Savage began stating chambered for 2 ¾ inch shells in their 1938 Fox catalogues.
All this being said there is a good body of evidence that back in those days chambers were held about 1/8 inch shorter than the shells for which they were intended. In the book The Parker Story
the Remington vintage specification sheets on pages 164 to 169 call for a chamber 1/8-inch shorter than the shell for which it is intended. Also in the 1930's there were a couple of articles in The American Rifleman
(July 1936 and March 1938) on the virtue of short chambers. A series by Sherman Bell in The Double Gun Journal
showed no significant increase in pressure from shooting shells in slightly short chambers. IMHO I don't much sweat that 1/8-inch in 12-gauge guns. On the other hand when one gets a 20-gauge chambered at 2 3/8-inch likely intended for 2 1/2-inch shells I do worry about folks firing 2 3/4-inch shells in such guns.
From the very earliest days of the 20-gauge in North America, the "standard" paper 20-gauge shell was 2 1/2 inches in length, though the manufacturers offered 2 3/4, 2 7/8 and 3-inch shells as well. The maximum load offered by the loading companies in the 2 1/2 inch 20-gauge shell was 2 1/4 drams of bulk smokeless powder and 7/8 ounce of shot, or 18 grains of dense smokeless powder such as Infallible or Ballistite and 7/8 ounce of shot. In the 2 3/4 inch and longer cases one could get 2 1/2 drams of bulk smokeless powder and 7/8 ounce of shot, or 20-grains of Ballistite or Infallible dense smokeless powder and 7/8 ounce of shot. The longer 2 7/8 and 3-inch cases got more and better wadding, which many serious shooters believed important. Like these 2 7/8 inch 20-gauge shells --
Progressive burning smokeless powders were an invention of WW-I and by 1922, Western Cartridge Co. introduced shotgun shells loaded with progressive burning powder. This was their Super-X load, put up in their 2 3/4 inch Field shell, pushing 1 1/4 ounces of shot in 12-gauge at higher velocities than previously possible and one ounce of shot in the 20-gauge. Manufacturers did not rush to start chambering their everyday 20-gauge guns for these new heavier 2 3/4 inch 20-gauge shells. I have a little 1930 Parker Bros. VH-Grade 20-gauge that is chambered for the 2 1/2 inch shells. Major North American ammunition manufacturers continued to offer the 2 1/2 inch 20-gauge shells until shortly after WW-II.