There's a new to me CZ P09 in my "dry fire range" as I get it worked up for USPSA. In one of the many Youtube videos I've been watching to get up to speed with this pistol one presenter mentioned that O rings were used as he was going to dry fire repeatedly throughout the video. That was the only mention. So, are o rings necessary for preserving this pistol since I usually do quite a bit of dry firing? If so, what's the placement...over the firing pin to prevent the hammer striking the firing pin?