Chambers on my 20 gauge Archived Message Posted by David on May 14, 2007, 8:04 pm I have a field grade 20 made in 1922 based on the serial number. It has 3" stamped on both barrel flats just underneath the proof marks.Does this mean it was chambered for 3" shells? Message Thread: Chambers on my 20 gauge - David May 14, 2007, 8:04 pm Re: Chambers on my 20 gauge - Bill Hambidge May 15, 2007, 6:18 am Re: Chambers on my 20 gauge - David May 15, 2007, 8:32 pm   Searching