No one can tell you over the internet what ammunition may or may not be suitable in a given gun.
It needs to be evaluated by a qualified smith with the proper tools for measuring barrel wall thickness, chambers, forcing cones, bores and chokes.
Ithaca Gun Co. was advertising some very light 16-gauges in 1913 --
Flues 16-gauge light weight Ad 1913.jpg
In my opinion one wants to be pretty careful feeding these 110-year-old Flues Models with their reputation of cracked frames and thin barrels.
No. 2 Krupp Pigeon, 1915.jpg