I have friends here in SC that have killed them with a variety of pistol cartridges including 40S&W, 45ACP, 357 and 44 mag. Everyone here uses pistols during the season just for ease of use and space. I've been on a couple hunts where gators were dispatched and the caliber doesn't seem to be as important as shot placement! Also, a sharpened bush axe is the great equalizer...always always always sever the spinal cord. I've seen numerous videos and heard a number of stories about "dead" gators coming back to life!!
Not something you want in the boat with you!!!