I had looked at the No. 345 pages in J. Stevens Arms & Tool Co. General Catalog No. 54 where the No. 345 was introduced and it didn't state chamber length. The later pocket catalogs of both J. Stevens Arms & Tool Co. and then J. Stevens Arms Co. state the No. 345 is "chambered for 2 1/2 inch shells" --



as most 20-gauge guns of that era were.