I understand your point in that there are martial arts that incorporate modern weapons. Probably a nit, though I'd consider 3-gun and IPSC sports or events rather than arts themselves. Similar to how people can practice and train in different martial arts, but when they compete there are specific rules they need to follow depending on the event they're participating in.

Like other martial arts, shooting sports have to be different from actual combat to avoid actually killing the participants. Some (e.g., paintball or tank biathlon) are more realistic than others (e.g., sumo).

Right. The distinction I'm making is between the training and what is done in the sporting events. People taking self defense courses which incorporate aspects of martial arts learn and practice some techniques which are not allowed or advantageous in a sporting event.