My 1930 vintage VH 20-gauge has the 2 3/8 inch chambers intended for the 2 1/2 inch shells. Your 2 9/16 inch may really be 2 5/8 inch, intended for 2 3/4 inch shells.
Parker Bros. policy was to chamber their guns 1/8 inch shorter than the intended shell. The theory back in the days was that the mouth of the shell extending a bit into the forcing cone upon firing gave a better gas seal and improved patterns. A.H. Fox Gun Co. also short chambered.
While Parker Bros. would chamber your gun for any length shells you wanted, pretty unlikely that a "made for stock" gun like the Trojan would be anything but their standard 2 3/8 inch chamber. Our North American ammunition companies continued to offer 2 1/2 inch 20-gauge shells until just after WW-II.
Victor 2 1-2 inch 20-gauge.jpg
Pretty hard to tell what may have been done to the chambers of these old guns in the hundred plus or minus years since they were made.
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