2&3/4 inch chamber
 

What year did Parker start 2&3/4 inch chambers on 20 gauge shotguns?

With certainty, 1985.

You might find a few in the late 1930’s, but then they were commonly 2 5/8”. Before the 30’s , 2 9/16.”.

Have you checked the chambers table in TPS Barrels chapter ?

Is this of importance to you and if so , why?

Present SAAMI standard extended case length 20ga is 2 5/8 to 2 3/4. The standard was extended in the 1950’s and proof and working pressure standards were increased.

The Remington era Parker specification sheets reproduced on pages 164 to 169 of The Parker Story call for the "normal" Parker 20-gauge chamber to be 2 5/8 inch intended for the 2 3/4 inch shell. "Other chamber depths optional"

During the years that Parker Bros. offered 20-gauge shotguns, the "standard" 20-gauge shell in North America was put up in a 2 1/2 inch case and the maximum load was 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. Longer cases -- 2 3/4, 2 7/8 and 3-inch -- were offered by our North American ammunition companies

Attachment 62298

and one could get a slightly hotter load of 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.

Attachment 62297

The main advantage of these longer shells was more/better wadding which many serious shooters considered important.

In 1922, Western Cartridge Co. introduced their progressive burning smokeless powder, high velocity, loads, Super-X, in 12-gauge (1 1/4 ounce) and 20-gauge (1 ounce), put up in their 2 3/4 inch FIELD shell.

Attachment 62299

Parker Bros. didn't rush to embrace the 2 3/4 inch 20-gauge shell. My 1930 vintage VH-Grade 20-gauge has the 2 3/8 inch chamber intended for the 2 1/2 inch shell.

Cxx

FWIW I have a 20 ga VH made in 1900 that letters with 2 5/8" chambers which would have been intended to use 2 3/4" shells.