Holding the Action (and Facing the Ring)
Many times, when working on the receiver, the use of jigs or holders can make life easier. One case is the squaring of the front of the receiver. This work is done in order to insure that the flange of the barrel tightens true and square with the axis of the boltway. With the action mounted in a lathe and centered, a very light cut is taken on the front of the receiver. The easiest way to hold and center the action is with a "receiver facing mandrel" (Brownells nomenclature).
Above are two mandrels. The upper one is by Brownells and is for a Large Ring Thread, while the lower one I made and is for the Small Ring Thread. The 0.700 x 10 inch long part extends through the boltway. Brownells gets $41 for a mandrel. If you have a lathe big enough to do actions, then you can make one. If turned between centers or held in a chuck or collet and not removed until done, you can be assured of its being as good as any factory made piece.
If you intend to make one, make both unthreaded shanks the same diameter (0.700-inch) and put center holes in each end. Learn by my mistakes J . Note the wrenching flats on the Brownells made mandrel, nice, but I haven't used them.
If, when inserting the mandrel and tightening the threads, the mandrel binds in the boltway, you have a bent or warped action.
Of course, if it is a K.KALE, the facing operation can also remove the upper handguard extension.
If you have a lot of spare time, this action holding block can be made. Brownells sells one for $50, but I don't think it accepts the trigger.
You can mount the action and use the block when polishing, or
hold the block in a vise for filing or ?