Have you looked at Tester's voting record? He as voted pretty much down the democratic line, opposed trump at nearly every turn. He is pro-illegal immigration, support sanctuary cities, Opposed trumps SCOTUS pic etc. I don't see a 2A vote as a US senator, but my guess is he would follow the Democratic line when the time comes. The problem with these "conservative" democrates is that they talk a conservative game, but they vote with the party on nearly very vote especially the cloture vote which is often much more than the final vote.
The collection of taxes which are not absolutely required, which do not beyond reasonable doubt contribute to public welfare, is only a species of legalized larceny. Under this Republic the rewards of industry belong to those who earn them. Coolidge