Killing turkey does not require a ton of power! what is required is to get a pellet in the neck or better yet the head. It only requires around 6 FT LB of energy to cleanly dispatch a turkey.
A 410 if legal is more than enough if you mind the distance. Inside 30 yards, no problem. The idea that a big bore 12G is required way is over blown. I have seen turkeys shot and killed with a Crossman C02 .22 with a clean head shot. Matter of fact in CA they now allow turkey hunting with a pellet gun. With cal as low as .117. Todays modern air guns using 18/30n FT LB of muzzle energy is a great tool for the job. It requires a good clean head shot. Drops them like a rock! Now i can see your eyes just a rolling. Ck out you tube. See for yourself. Hunting larger game using lighter equipment is like big game fishing on light tackle.
Its requires a higher level of skill. No cheap over powered shots from a big bore.
You either make a clean kill or a miss. Many less crippled birds.