Amarillo - I dunno. I'm having a hard time thinking of a gun that has thinner ribs than a Model 21 - I've got a five pounds, three ounce, 28" bbl 20 gauge that has more rib than a 12 gauge 21. Interesting topic in itself. I'll have to go up and down the street and ask to turn the neighbors' 21s upside down and take a look.