Astute observation Dean. Read the story about how Ernie Simmons altered a Model 21 20 gauge-refitted it with M37 .410 barrels for sub-bore skeet, around 1940 maybe. John Olin saw it, got excited and ordered Dave Carlsen to build a production prototype on a 28 gauge M21 (same basic frame as 20, just milled out I believe)and one of the alledged outcomes from this "experiment" was the milling off of the receiver side bolsters- hence the "flatside" M21 design- Lotsa fuss and feathers for a dinky gauge, but I'm a duck hunter, not a skeet/clays man, and like Nash B. believe the .410 should be banned for hunting. Now Parker Ackley's rebarreling a Model 1897 12 gauge into a 30-06, that was a whole 'nother ballgame, IMO!! RWTF
