Well, speaking from experience as an IPSC competitor and as a firearms instructor my LE agency, practical pistol competition is about as realistic when compared to combat shooting as sport fencing (something else I've done in national competition) is to a real sword fight.
I once upon a time figured that (as a sport shooter in pistol and rifle since I was a wee lad in Jr. Hi) I'd do what you are thinking in Traveller, but back then I couldn't figure out how it would make much difference. A character with a high skill rating could, under the broad interpretations of CT, be considered either (or both) an experienced combat vet or Olympic level shooter. I let it lie as both in MTU.
Now, older and wiser with real life experience in both competition and life or death combat, I have decided to also let it lie as is. The only way to otherwise do it in a strictly realistic sense, IMHO, would be to penalize the player if his skill is in sport shooting and in combat, and penalize the combat shooter trying to win in sport competition. For example, all the single-minded hit the center of the bullseye and take the full 10 seconds to do it I had learned from competitive shooting (non-practical) went out the window when I learned real combat shooting where the last nine seconds might cost you your life. Same with IPSC: yeah, I can drill out a set in a few seconds, but I'm racing against a clock through a contrived drill and using a racegun totally unlike the Glock I carry on the street. And no one is shooting back at me or at someone else while I'm doing it so the feel isn't the same.
Not to discourage you, I guess it just depends on your level of realistic simulation. Maybe a separate skill? Or it equates to a faster training program for skill levels?