When I was about 12 or so I got an old single shot 20 ga. Stevens IIRC, that would just hammer me. I spent the next few years scared to give a 12 ga. a try -- 20 was enough. That sucker must of been choked hard or something because when I finally started shooting some 12s, I don't think that I've found one yet that kicked like that 20 did.
It sat in my gun case after that for 10 or 15 years until a bud asked me if I knew of anybody that had a 20 ga that they would make a good deal on. I guess he had this idea that he was gonna start bringing his grouchy wife along duck and pheasant hunting with us sometimes and wanted to break her in with a 20 ga. so she wouldn't get sore and want to stay home -- I had just the deal for him. Ha ha ha ha ha she never did come out with us.