From:

Inspectorate
Provisional Standard

REME Central
File No: 7/IW/Gen
Issue 1, 1957

Striker protrusion:

Gauge, Armourers, No. SM 143

In post WW2 Oz, this (or its locally made equivalent) had the NSN of 5220-99-961-9944.

Max: 0.050",Min 0.040"

Viz:

"f. Striker protrusion is within the limits of 0.050 inch high, 0.040 inch low and the point is radiused 0.038 inch.

Note: Adjust by stoning the point of striker if too high, ensuring radius of 0.038 inch is maintained. Stone tenon of bolt head if low, ensuring face of tenon is kept square and that “lift” of cocking piece is within limits of sub-paragraph 2.e, otherwise, exchange striker."

Note the second sentence of that "Note":

If you are going to adjust anything, stone the REAR of the threaded tenon, NOT the face of the bolthead. There are two reasons for this:

Firstly, removing metal from the front face WILL enlarge the headspace.

Secondly, because the mating hole for the striker is TAPERED; "adjusting" the face will effectively enlarge the hole by a whisker AND it will remove some of the VERY thin hard skin.

The finished radius of the tip of the striker is important. You do not want a "truncated cone" like the tip of an SKS striker, unless you have a fetish for ruptured primers.

The bit about maintaining the "lift of the cocking piece" is kinda important, too