As far as I'm concerned, I don't trust ANY politician's stand on RTKBA - Bush or otherwise. Though I do believe that GW stands on principles more than any pol I've seen in a while, a pol can always be depended upon to sway with the wind when it comes to popular opinion. Clinton went with the AW ban because his pollsters thought it was a winning issue - they were wrong and the issue sunk many house and senate members of his party who were too intimidated to openly oppose him on it.
No, gun control issues are a matter of voter reactions. As long as the pro 2A crowds stick together in voting masses, more pols will at least take a position that either agrees with that mass or not tick them off. Its all a matter of political power, not which pol believes what.