Make it an organized task at the next meeting of your gun club. Do NOT use form letters. Each of those is counted as one voter, but each personal letter is counted as 500 voters, because so few actually write. If you want to speak as the voice of 500 voters, write one letter. If you want to be more politically powerful, write more ltters yourself, and persuade others to write.
Politicians have three major self-interests.
I want to be nominated to run in the next election. I want to win my seat in the next election. I want my Party to win the most seats in the next election. NFA Your enemy is never a villain in his own eyes. Try to see things from his perspective, and you may find a way to make him your friend.