re: Pheasant hunting gauge?

If you are hunting over Dogs get a 20. Shoot light magnums in 5 or 6. I use a 28 and shoot win mags 1oz 5 and have no issues MOST of the time. You will want to throw that 16 into the weeds as they kick like a 12 and weigh the same. Weight is the issue as you might walk 5-6 miles in the AM.
You need dogs as if you shoot one far off you won't ever find it.

20 ga is plenty even for 40 yard shots, they ain't that tough really.