Grunting is absolutely useless here. I have never grunted in a buck. The can is pretty useless 99% of the time but the 1% that it works it works very well. It's about the same thing rattling. I have rattled in some deer but I rattle 30-40 times for every response I get. Hunting open fields is another. It is normally a rare occurence that mature bucks come into an open field that happens mostly during the rut.