Check your state's game laws and find out what the legal minimum draw weight is. It's 40 in Texas but some states say 45 and some don't have any draw weight minimum at all. But you're right. A well tuned 40 pound recurve & razor sharp cut on contact head will definitely kill anything deer size and smaller. That is, as long as shot distance is reasonable and shot placement is good. I'd say to keep arrow weight up between 400-500 grains though.