I'm not sure if I can help, when I served we were issued with and responsible for our individual breech blocks(each individually die-pressed) but that was with L1A1 SLR's, which in the relative times may have occurred with the .303 issue. I do know however that we had bunkers full of Thomson, Bren and .303's greased and crated well into the 1980's. The Lithgow Museum may be a very good start, unfortunately my memories of Lithgow are of freezing whilst trying to rebuild turbines at Mt.Piper Best Wishes!!