actually the best custom action is BAT machine. they machine the scope rail AND recoil lug into the action. this makes the action stiff as hell and you have the barrel shank tightened up against a recoil lug that WILL not move. you can pin a 700 lug or have some fancy way of attaching it, but its still not part of the action. not part of the action = not as gooooud. the bat action is a bank vault, it has tight tolerances but the spiral flutes are good at keeping it running. I have shot .5 moa at 500 yards with it with a wind that was gusting 5-6 mph left to right without adjusting my wind holds, vertical spread was 3/4". this is with a #5 barrel. only problem now is I want more bat machine actions.
