20 Gauge seems pretty good.

I got to play with a 20 gauge coach gun (again, I did not make a note about make and model. Yes, I am that absent minded) and I am going to say that I would not want to stand in front of that thing when it goes off.

This is two loads of buckshot. One is Aguila #2 buckshot and the other is Winchester Defender #3 copper-plated buckshot. In my uneducated opinion, they both performed nicely in the gel.

One load of each Aguila and Winchester in the gel. Boards are 2x6

And this is Winchester 20 gauge 3/4 oz. slug after recovered from the gel. I did not take a photo while in the gel, but it went easily to the middle of the field of buck seen above and as you can see, expanded nicely.

The coach gun was a light one and even so, the perceived recoil was distinctively less that with a 12 gauge pump. I may have shot 20 rounds of both types and yes, I have a bit of soreness, but it is about the same if I had slept with the arm the wrong way or any other of the aches I have related to getting old.

I would say anybody who is recoil sensitive with a 12 gauge, would want to consider “downgrade” to a 20 gauge without feeling to have compromised performance.