Yeah, Bull, I went teal hunting a few times with my 20 gauge thinking it'd have the advantage of quicker swing on those little beggers and it just sucked.
I was shooting 3" number 4 steel. Not only is number 4 a bit light, but 20 in a 3" just doesn't pattern like a 12. So, I went back to my 12 REAL quick.
20s are for doves.
I used to shoot 3" steel number 1 or 2, but I find 2 3/4" fasteel or Winchester HV (over 1500 fps) to be deadly. This allows me to shoot my old Winchester 1400 auto that has a 2 3/4" only chamber. I've got 12s. 20s have their place, but that place ain't in the marsh!
My lovely wife bought me a gun I'd been drooling over at an ag supply in a local town. We'd go by there after church and I'd ooh and aah over it. It's a 20 gauge CZ Redhead Delux O/U, fits like a well tailored suit. She was going to give it to me for Xmas, but in mid december, friends from Waco came down for a goose hunting get together and my wife brings me the CZ, says she thought I might want it for the goose hunting trip.
I had to explain to her that my 10 gauge was more appropriate, but I will use the HECK out of that 20 opening weekend of dove season!
You know, if one tool could do it all, life would be boring and I wouldn't need another gun safe. But, such is not the case.
The .223 cannot do anything any of my bolt guns can't do better. We do have yotes, but I'm not really into hunting 'em. BUT, there's a place in my rifle collection for the M4. If nothing else, it's a fun plinker and the factory ammo is so cheap, it's as cheap or cheaper than .22 magnum. I don't even bother handloading plinking ammo. One thing I'll hunt with it is turkey. I took one with my .22 mag couple of years ago. This year, I didn't score, but I carried the M4 with FMJ. Figured putting out 4 times the energy of .22 mag, an expanding bullet would just waste meat.
I've learned to carry the thing on a 2 point sling such that it hangs by my side in the field and grabbing it for a shot is quicker than drawing a side arm. It's light bumming around in the woods, too. I'd always disliked ARs for the ergos of carry afield, but after I got one, I learned to properly use a sling with it, a LONG sling, not your average Walmart sling.
Yes, I may never kill a deer with it, but I still like the thing.