dont know Dave. I wouldnt want to be on a boat with a guy brndishing a submachine gun and having him fire holes ino the craft. A shotgun will do fine. Anyway, when you are out and see a fast boat attempting to close from a wide angle, I usually have time for a distress and to load up.
The thing about boats (power boats mostly), you get a feel early for when a nearby craft is acting weirdly wrt my course. You can usually take a jog to port or starboard and see that he adjusts his coarse with you, then I begin to be concerned.
Remember, with good instruments you can see pretty much "over the horizon" (BUT, so can he).