The advice to look at the AA 400 is good but I do not believe you absolutely must have a regulated one ... but opinions differ between people. I used the standard 400 for a long time and got my best ever 58 in HFT with it. The single shot is ideal for competition use as you don't end up messing around with removing the magazine between lanes.
I can't comment on hunting as I don't do that.
Cheers, Phil