Grant, in looking up your serial number, it is from 1936, and in this year the 20 gauge went from 2 1/2" to 2 3/4". As Tom Martin stated, unless there were shorter or longer chambers made in a time when the standards were either 2 1/2" or 2 3/4", then there would be a chamber stamp showing such on the barrels water table.
Most of the 16 gauges in 1936 were 2 9/16" chambers, and I have one from 1939 that still has 2 9/16" chambers. This was also the first year noted in a catalog of the SSP or Single Sighting Plane which was a higher rib and was an option of $5.00 extra.
As to the chokes, unless ordered different, they were sent from the factory with full/full no matter what grade or gauge.
I do believe that yours was opened to 2 3/4".
Last edited by JDW; 11/08/12 12:13 PM.
