It kind of sounds like Jack got a new toy and was trying to show it off. I could also see a little bit of "Look how awesome and cool and strong and tough I am!" in there, as well.
That being said, I have no problem with people having guns. My mom, my sister, my in laws, my husband - they all have carry licenses, and they use them. That being said, other than a quick discussion about the pros/cons of particular models, none of them have ever felt the need to show off their weapons. Which is why I personally am of the particular mindset that if one needs to brag about toting, one probably shouldn't be.
So, in my family - wearing it during dinner - fine, but odd. Taking it out and showing it off around small, impressionable children, on the other hand, would warrant someone saying something. Safety trumps etiquette, and it's just not safe to show off a loaded gun like that.