Well I don't know anything about an ORF tool, but you will probably need to use something like a socket extension, etc and push with the barrel pointing down. Since you can't get right behind it, you can use a piece of metal placed through the magazine well so it sticks out on the top and bottom sides, then put blocks underneath the metal to support it. That way it will only press the barrel down a little bit until it hits the supports. That should do the trick.