The idea of a thumb trigger in place of a traditional index finger trigger has come up a number of times in firearms history (the Pieri carbines tested in France and Italy, the Winchester Thumb Trigger .22, etc). The most recent iteration (and the first semiauto one, as far as I can tell) is Iron Horse's "TOR", or "Thumb Operated Receiver". It's pretty simple in operation, with the trigger located high in the back of the grip and actuated by the thumb. It is suggested that this style will be better for precision shooting, better in cold weather, and better for people with a handicap that inhibits use of the index finger. Well, the one of those I can test out here in Arizona is precision shooting...so let's see how the thumb trigger compares to a traditional trigger, with all else remaining the same.