Gap between barrel and receiver

[Bruce_in_Oz]

But, wait; there's MORE! as they say in the classics.....

After successfully tinkering with the lawnmower, I did a bit of a dig in the crypt.

No4 data re. breeching is as follows:

Distance from front face of receiver to inner breech ring: 0.701" + 0.005". (Taken from the 1961 version of the drawing for the Mk 4 pattern receiver.)

Distance from rear of threaded tenon to Knox form shoulder: 0.696" Max, 0.693" Min

Caveat; those figures for the barrel are from the drawing for the Australian "Barrel No4 .303 (AUST)" which was produced for the rifle clubs in the 1960s. The drawing is dated 12Mar1965 and the only obvious difference is at the pointy end. The muzzle has the external "cone" feature for easing the bayonet into alignment but is devoid of bayonet lugs. Do any forummers own one of these barrels?

There was allegedly a 7.62 NATO version of this barrel also produced at Lithgow, but I have neither a sample nor a drawing. Any clues?