Trap shooting - is 20ga as good as 12ga?

Your best bet is to go out and see a few trap-dedicatd guns. 20 ga is more than enough to break every presentation on a trap field, but the setup of the gun is really what facilitates you doin so. Because of target presentations, you want a high rib gun, or at the very least, an adjustable comb so you can move your point of impact on the clay. You're shooting at rising targets, so using a field model, lets say a Benelli Legacy, puts you at a real disadvantage. Using that shotgun, you need to COVER the target on multiple presentations, and it's not only unnatural, but when you do so, you slow your muzzle because you lost sight of the target. Check out shotguns like the Beretta DT10 Trap, or Luitics, and see what features they have on them. You can find semi-auto trap guns from Beretta in the form of the Model 391. 1-1/8 oz is always preferred, as more pellets mean more pattern. BUT if you shoot a modified choke with a 1 oz or 7/8 oz load in 20 ga, you'll be fine. You may find it easier to shoot multiple rounds, as the recoil is significantly less. I find myself reloading my 12 ga loads with 1 oz of shot and even 7/8 for practice, as I can concentrate on 300 rounds and never get recoil fatigue. A great book to help you get started is Gun Digests Guide to Trap shooting. Once you get out there, check out sporting clays as well... thats the challenge....