I love the 20g. I have quite a few of them. A 30" M21, at about 7 lbs would be a really nice clays gun. For the field, I like a 20g around 6 1/4 lbs.
20g is just as cheap, if not cheaper to shoot as 12g. It'll knock any upland bird out of the sky with authority, given the right load. For dove, it's more than enough, IMO. I started shooting a 20g with my buddies in weekly rounds of clays and fun shoots about 6-8 yrs ago. At first I thought I was handicapped. Not for long though. After a little while, I didn't even think of the guage difference. When I shoot clays now, I use mostly a 20 with some periodic 410 shooting. Some of my best clays scores were with a 20g. Try it for a while, you'll probably never go back to a 12g.
