No1Mk111 Receiver Holding Fixture

By definition, it MUST be! The striker must be accurately in line with the primer which is in line with......... which is.......

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Originally Posted by tbonesmith

Or maybe at the rear the mandrel could be made 20 thou undersized to allow a brass or steel bushing made to fit the individual rifle to be sleeved over? Hmmm...

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Could be, although it would not give any positive "lock" between the mandrel and the body, unless some form of adhesive or soft solder were used. I wondered if a mandrel split into two halves might be better, but thinking about it in cross-section the four way split would be more likely to grip evenly and align accurately if the slits were aligned with one vertical in the bolt way.

A driving lug made to bear against the side of the "cocking piece recess" in the butt socket could be threaded or soldered onto the mandrel; or welded/brazed/silver soldered if the mandrel was finish machined/ground afterwards(?)

Thinking a little more, a long taper on the lug which would just fit the recess might be better: insert the mandrel until the lug bears on both sides of the recess. That way one could rotate both directions if a dividing head was in use.

Actually, there would be a tendency for the mandrel to work itself out with a tapered lug, even with a long taper....maybe ditch the taper idea and just make it parallel sided, but undersize 10 or 20 thou and shim it in with brass shim stock on either side. Make it 40+ thou shallower than the recess so there would be no chance of the mandrel being pushed upwards by the lug & shim hitting the bottom of the recess?

And going back a couple of steps, the mandrel would need to be counterbored down to the point where the expansion was wanted so that the threads and therefore expansion would not occur before that point. Totally obvious that I guess.

You lock the bolt-way mandrill into the bolt way using a bolt through the existing safety catch hole through the body and screwed into the well fitting mandrill. Easy!

Much better idea, Peter.

I would be very worried the mechanical advantage of any split bush/ mandrel and wedge type set up would impart onto the open sided bore of the boltway. It would not take too much pressure there to begin to distort the receiver.

So not tightening the bolt down against any part of the body Peter?

As for distorting the body Son, one could run the bolt into the mandrel first and then grind or turn the OD down to exactly the "spread" size wanted. ;)

No tightening as such required Rob. All you are aiming to do is secure the mandrill in the body