I figured that they had some sort of "official' background or had come from UKicon or Canadaicon. The only people in Oz who put proofs on stuff seem to be Thales / ADI / Lithgowicon.

Definitely 7.62; dummy rounds and 7.62 headspace gauges won't fit a .303!

Extractor slot is a little wider than .303 type, as well.

Definitely need a breeching washer.

The question now is; where do these fit with the "purists" if I bundle up a bunch of parts and build myself a clone of an L8 for competition work?

Despite having a "real" ordnance produced and proofed barrel, will it be even less Kosher than my old "bitza" No4 Mk2 with its .30" / .308" barrel (chambered for .303 but custom throated for .30 cal 168gn Sierra Matchkings)?

Is .303 service rifle shooting going to wither because nobody can get decent quantities of "real" .303 ammo and thus resort to commercial, boat-tailed bullets that will eat their barrels?

Are the "rule nazis" going to insist that the " club regulations" are more important than getting people on the mound and safely shooting the MATCHES? Great way to make people walk away.