Bro. Brent: think hard on this. A 6# 2 1/2" chamber vintage 20g, even if full and more full, is probably not the best choice for late season wild Iowa pheasants. Lose a few that have been hit, and the good idea won't seem so good.
Might I suggest a pre-1913 Smith or a Fox in 16 gauge, 6 1/2#, with forcing cones lengthened but original chambers and the head of (either) stock glasbedded. You could use anything from the RSTs 3/4 oz. load up to 1 1/8 oz. pheasant whackers.

Bro. Larry will be along to point out a 6 1/2# British 12g would do it all also, and he'd be correct wink

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