I have actually been wondering the same thing quite recently. I tend to prefer the .45 and 12ga but have recently begun considering what rifle calibre might be most available and therefore most easily attainable when ammo stocks need repleneshing? 5.56mm, .257, 30-30, 30-06, .308, it all gets rather confusing after a bit...
Also, what other guages than the 12ga would be good to concentrate on?
My personal opinion is that there are no other gauges besides 12 ga. You can get reduced recoil in 12 ga. You can get tactical loads. You can get birdshot, skeet loads, turkey loads. Why buy another weapon?
12ga is really the only shotgun I’m familiar with, although I have Grandpa’s single barrel 10ga. That thing’s a bear to shoot. I’m guessing .410 would be a easily stockable commodity.
Stick with the 12 ga...
there are some cool “utility rounds” that you can get for it.
flame thrower, fletchet, flare, slug, etc
12 or 20 unless you have one of the combination .22 LR/.410 arms, then .410 Some pistols will take .410 shotshells, too.
I have taken whitetail deer with a .410 (rifled slug)