No 4 Mk 1 markings confusion

[Surpmil]

In the Library are Peter Laidlers "How To" series of Armourers Instructions. To assist here is an extract from the 'fitting bolts' section.


First things first. Bolts could only be fitted at Field and Base workshops because they were the only ones that had a 'GAUGE, Inspectors, Bolt'. This is a brand new, calibrated bolt. Still in white metal and marked as such. If my memory serves me right, the slot in the long/top locking lug is machined right through to identify it. So that's the reason if you have ever seen one. This bolt is bare. Clean the locking lug surfaces of the rifle and put a smear of 'engineers blue' marking dye onto the corresponding locking surfaces of the inspectors bolt. Insert this bolt RIGHT FORWARD, rotate it closed, then draw it backwards and forwards a couple of times to mark the mating locking surfaces of the rifle. Push it forwards, unlock and remove.
Examine the locking surfaces of the rifle. The blue witness marks should be evident. This ensures that whatever wear that has taken place on the rifle locking surfaces has taken place equally. If its not, then I'm afraid that the rifle is unserviceable.

BUT, that's not quite the end of the story because you won't have this 'Gauge, Inspectors, bolt' but it's only right that I tell you. Now for a little secret. If you have ever bought a rifle that has a sploge of red paint on the left side, adjacent to the internal left side locking lug, then you now know that the rifle was condemned for 'worn locking lugs'.
If you are going to fit a second hand or new bolt, then do the same thing. If the dye pattern is one sided, then stone the high surface of the bolt until BOTH locking lugs bear evenly against the locking surfaces of the corresponding surfaces in the body. BUT DO NOT ATTEMPT to stone the rifle to get a bolt to fit (you can only get to the right hand surface in any case ....). The rifle body is induction hardened at these points to a depth of .004 - .006" but we have found it deeper.

Interesting. A couple of questions: we all know the bolts can be quite loose in the boltways of some bodies, particularly without the bolthead fitted. The reason I suggested applying backward pressure to the end of the bolt was because it seemed logical to try to duplicate the alignment and pressures which the bolt would have on firing.

If one was to simply apply rearward pressure with the bolt handle, would not the leverage of the handle tend to pull the bolt body to the right and therefore slightly out of its typical firing alignment, particularly without a bolt head fitted?

And as for using the Gauge, Inspector's, Bolt, perhaps there is something missing from that text as surely the critical question is whether the two pairs of lugs are each bearing evenly, not the relative position of each pair to the other?

Presumably somewhere there is a drawing the Gauge, Inspector's Bolt was patterned after, but I can't see why it would matter whether the body lugs bore evenly against that gauge as long as they bore evenly against the bolt fitted to the rifle!?