.303, helping Englishmen express their feelings since 1889
My guess would be a .22 liner bonded into a 7.62mm barrel.
Judicious use of a Pantograph machine might possibly be involved, who knows....
Only Kev can give us chapter and verse regarding the apparent Lithgow.22 factory builds.
I've never heard of such a rifle in all my years of studying the breed and
I can find zero reference in Ian Skennertons 'SLR Australia's Fal' or for that matter, in my Collector Grade The Fal Rifle, the complete history.
So .....
.303, helping Englishmen express their feelings since 1889