1) If you're writing Levin in a thing directly relating to a specific bill, you're gonna get blown off. His people have decided that the vote he needs are more in favor than opposed, so he has written you off.
2) If you're writing other congresscritters, you can use Levin as a bad example. That'll get back to him, and he may think about what he does in the future.
About the only way to reach a congresscritter who has gun control as part of his or her platform is to make them say to theirselves "Hey, if I do this, it could be overall bad for the party." If you have their peers dumping on them, that's even better.
"Uh, ahem... Honorable Mr. Levin? If you keep doing this, it's going to cost us elections. We cannot afford that."