I don't understand the supposed "issue" of ammo availability for 16ga. I can go to six stores in my relatively small town and find what I want any day of the week, year around. Walmart always has it, our sporting goods stores all have it. I have never ever had trouble finding it except during times when you couldn't find any ammo of any kind.
There is still a pretty limited supply of ammo for rare calibers here. I can find most things... but cant find any .284 win. Cant find any 410 that isnt defense rounds. Maybe South Dakota gets some priority due to the pheasant hunting. Not much shotgun stuff goes on in NE Wyoming. To my knowledge, there isnt any 16 gauge on the shelf here right now either, so finding it for 50% in Rapid City was surprising to me, and I bought a few boxes. Ordered a case when I got home.
