I have no idea what Doug's agenda is now, but lots of examples of chamber markings here http://www.picturetrail.com/sfx/album/view/19686599

This 1928 20g Field grade with 2 3/4" stamp is courtesy of Jim Akins.



It is not clear if this was a special order stamp or if placed after chamber lengthening.
20 gauge chambers were lengthened from 2 1/2" to 2 3/4" about 1936, and usually were NOT stamped thereafter, by Hunter Arms or Marlin, unless 3". David's is interesting.

I have never seen a chamber length stamp on the barrels. This a Marlin era 20g



I personally would glasbed the head of the stock and then shoot 3/4 or 7/8 oz. loads at targets, and 1 oz. loads for pheasants without concern.

Will await Doug Somebody's correction of our collective confusion, but believe this childish game is unbecoming and have no interest in participating

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