Dave if the gun was sent to Buck and the chambers were lengthened before, you should have had him glas bed the locks and this way you could be shooting most 16 gauge loads without having to pay a premium.
The chambers were changed to 2 3/4" sometime in late 1930 or early 1940 as I have a 1939 that is still 2 9/16". The early 2 3/4" chambered guns had that written on the barrel's water table below the serial number.
I'm not sure when they changed the bore size to .660, but I have a 1927 Specialty that still has .650 bores.
The 16 gauge is my favorite.
