Cow calls during modern firearm can be used but due to the numbers of hunters on public land and, more importantly, the number of cow tags given out I use it sparingly. I've jumped elk before and stopped them with a cow call to get a shot. One bull stopped three different times as I was chasing him up a hill before I got the shot. The bull I shot last year I stopped with a cow call as he was heading over the hill in front of me.