I'm a gunner. It didn't come from a place of desiring to show off for other people -- it happened because I was (and still am) irrepressible, and I grew deeply agitated at the long silences. I have tried to control it for my entire life, but as a rule of thumb I found that the only way that I could avoid talking was to disengage completely from the material. I spent entire semesters browsing Facebook in class and teaching myself from the book (and conversations with the teacher) afterwards because if I looked up from my computer screen my mind would start buzzing with the implications of what the teacher was saying and I would quickly start commenting too much.
When I got to college I decided that if I was going to talk anyway, I would at least try to be useful about it. So I did a couple things.
1. I always waited for the awkward silences, and tried to ask the most useful questions I could.
2. I acted as a volunteer meat-shield for the other students. We had some professors who didn't just call on others -- they picked on them, not with intentional malice, but the soft teasing agitated the students who were picked, badly. So I sat myself front-and-center in the classroom and became a loudmouth to draw the bitter remarks from the teacher. The teacher loved it. I was happy with it; I had a good sense of humor and one of the teachers, in particular, was a good guy. He was just irrepressibly sarcastic, the way I was irrepressibly talkative. We made a good team. The other students thanked me for it.
Later, in graduate school, I learned to force myself to be quiet, and discovered that when I am silent (or absent) one of two things happen.
1. There are other, slower gunners in the classroom. For years I thought I was the only one who wanted to talk, but I realized that there are quite a few who subconsciously do a form of turn-taking where they wait to see if there are any "first-takers" and only pipe up after they're confident there are none.
2. Nobody speaks up at all. This happened in several brown-bag discussion sections where everyone just sat quietly and let the teachers talk to each other. After I realized that I was one of the few students willing to talk, I started piping up -- and still had to deal with an occasional sense of resentment from others. Sometimes people will target you because they imagine they'll be brave in your absence, but in reality, they won't. That's just life.
Generally, though, it was the first one. If you're able to repress yourself, then I recommend trying to keep quiet for several classes to see what new dynamic emerges when you're silent. Often it's engaging. If you can't repress yourself (like me: I have ADHD) then I think your strategy is great--be the good gunner.
As I've grown older, I boiled it all down to a simple maxim. Let other people take up as much space as you can, and don't grab for it senselessly. But, barring that, never apologize for the space you take up. It's you, after all. Don't collapse inward on yourself, and trust your peers to correct you gently if it gets out of hand--many of them are good people, even if they're put off by your talking, and they'll create the subtle social pressure that helps you curb yourself just enough to accommodate them while being you.
J
