I have 2 28 gauge guns made in 1936 as your gun. The DHE 28 gauge skeet will accept a 2 7/8 paper shell thats from the same era. My VHE 28 guage will not accept the 2 7/8 shell but chambers the 2 3/4. Neither of the guns have the chambers listed in the factory letters. I wish that the early Meriden made Remington Parkers would have stamped the chamber size on the guns like they did when they moved to Ilion.

Visually there is not a lot of difference in the various loaded 28-gauge shells --

Attachment 133983

From left to right --

1. Remington Shur Shot 2 1/2-inch, roll crimp, loaded length 2.357-inch

2. Western Super-X 2 7/8-inch, roll crimp, loaded length 2.612-inch

3. Western Super-X 2 7/8-inch, Super Seal crimp, loaded length 2.495-inch

4. Western Super-X 2 3/4-inch, Super Seal crimp, loaded length 2.425-inch

Looking through some of my stuff on another subject I found that a very late Parker 28-gauge from the September 2023 G & D auction had the hang-tag and it states, "Chambered for 2 7/8 inch shell."

Attachment 134631

The SAAMI meeting where it was suggested that manufacturers begin marking the chamber length on their shotguns was in 1937. On Savage made A.H. Fox guns I see the chamber length markings on some 1938 guns but fully in use on 1939 guns. In my Remington pumps and autoloaders I see barrels with date codes as late as December 1940 that just have the gauge but no chamber length.