No1Mk111 Receiver Holding Fixture

[tbonesmith]

You just gotta go with the axis of the bolt which is important in respect of fitting telescopes because you KNOW that the axis if the bolt is (? or VERY close to) the axis of the bore.

How you do it without unbreeching is....., phew!

Im thinking of doing it unbreeched, on a mandrel through the boltway, threaded into the receiver that has been machined between centres from a scrap .223 barrel. Im thinking the mandrel could be maching with 3 flats on the driving end to make it indexable in a 3 jaw chuck in the dividing head, making it removable and accurately replacable in the mill/dividing head while giving a very close visual approximation of the bore axis through the hollow mandrel. This would allow the body to be machined, removed from the mill, checked for collimation visually, replaced accurately on the mill and adjusted as necessary so you could sneak up on the collimation without having to spend forever resetting everything.