You can trust the transfer because of a couple of different reasons. No one who takes your money and fails to deliver the firearm will ever sell here again. You have a legal and very easy to prove case if someone did so. The posts here on the forum and the emails back and forth from buyer to seller would be enough to get a judge to hammer someone who might do something like this. Also you're talking about a firearm, specifically a handgun. Anytime things start going south on a firearm sale the cops start getting interested very quickly.