As said, its not rocket science... They make all different size bushings if you didnt know, if the front is 704 you use a 704, if the rear is 702 you use a 702, etc, etc. The center of those bushings is always the center. No tapered bushings to cock in there, just precision cylindrical ground bushings tight fitting in the raceway. You slip your 0.500 ground rod in there, or some use the 705 raceway reamer itself which also works. That is the center of your bolt raceway and what everything else should be lined up with.
Here is where probably the majority of guys screw up. If you use an old huge action truing fixture with the 8 big jack screws in it (Viper style), 95% chance you are going to put undue stress into that action before truing it, and it probably will show runout after truing. Ever wonder why once you dial in the action with that style fixture you cant get the indicating rod back out of the bushings? IMO the only proper way to hold onto a remington action is ONLY by the front ring. No matter how tight you clamp onto that front ring with that style fixture the indicating rod slides right back out nice and easy, this means no stress and good work holding.
Dont just say everybody finds misalignment with trued actions and try to make everyone believe that. You should be able to true an action, come back to it in a week, dial it back in to the raceway, and its not like everything magically came back out of alignment on the face/lugs/threads. This is probably due to the fact Im not using a shadetree truing kit, AKA a tap to true the face/threads, rather single point cutting everything. A tap is always just going to follow the path of least resistance, no matter how rigid you might think its pilot is.
It aint rocket science and "an old indian trick done with smoke and mirrors" 
