I've taken many groups out when multiple hunters could have shot simultaneously....and I've seen it tried....Success is much higher when the second and third shooters fire "on report". Had two hunters here on the ranch this year on muley's, second fired on report. Two 26 inc bucks on the ground. Bucks (and elk) will tend jump at the sound of the shot, then freeze, so need to wait that split second, then fire.... When folks try to fire simultaneously one seems to always shoot on the "jump" and miss or wound.....