The problem is that they are not obliged to publish your letter: they control what they put into the newspaper and what they don't.
So it is most unlikely that they will publish something they don't have a good answer for given that they clearly lean toward gun legislation.
Seems to me that if one is pro-gun and publish in a pro-gun paper/magazine then it's preaching to the converted and so it's really a waste of time.
If one is pro-gun and try to publish in a pro-gun control paper/magazine then you'll rarely get any exposure, and so it's really a waste of time.
I can't help but feel that independent channels such as the internet or unedited channels such as live phone-ins are the best way to at least get one's message across to all to at least hear and then hopefully consider those views.
Never say never, but as you speculated, I think it unlikely that this will get published.
You cannot wake someone who is pretending to sleep. Stop pretending. Wake up.
Freedom: Please enjoy responsibly.