The thing that most people don't realize is that a 10, 12, 16, 20, 28 or 410 gauge shot guns all have the same killing power, the difference is the amount of pellets in the load / pattern but a #2 steel pellet fired at 1500 FPS has the exact same killing power no matter which shotgun gauge it comes out of.
I laugh when I hear guy's say they need 12ga 3 1/2" magnum for geese so they can reach way out there .............. horse pukky ......... a 3 1/2" #2 @ 1500 or a 2 3/4" #2@ 1500 or a 28 ga #2 @ 1500 have the same kinetic energy and killing power at any given distance, of course a 3 1/2" has a 1 5/8 oz payload, the 2 3/4" has a 1 1/16 oz payload and the 28 ga has a 1 oz payload so less pellets in the pattern but each pellet has the same killing power. The only difference in killing power is that the 3 1/2" magnums are killing your wallet at $50 + per box and at the end of the day you need something to kill your headache from getting pounded by them, but hey they are hyped and pushed by the manufacturers and some people suck that hype up like free drinks at the bar on Saturday night..