Seek and ye shall find (old masonic proverb.....) As a matter of historical interest, these are called 'taper-lock' screws and were a pre-war/30's answer to prevent overtightening screws. As the internal and external tapers meet, they lock and it is impossible to overtighten the screw. The reason for it's use on the telescope tube (and in use on the Boys rifle too) was to prevent the cradles from being drawn down too tightly on the thin telescope tube and crushing it.
Alas, those who have used standard 'crushable' rings on No32 telescopes in the past have found to their cost - or if not their cost, then the telescope repairers annoyance - that the tube has been crushed behind the erector cell and stripping inevitably means destroying the erector.
There, another bit of useless Lee Enfield history that you probably never thought or knew about