Lee Enfield chamber reaming in the Great war?

[Lee Enfield]

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The Lithgow rifles had the bolt carriageway reamed to allow more clearance, as sand was binding the close tolerance actions and the increased leadin bevel was also done.
British actions had more tolerance in the chambers than the Australian ones,
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My understanding was/is that in 1915 the tolerances were changed due (mainly) to experience in Palestine.

Supposedly the original SMLE bolt diameter minimum (-) was changed to become the standard, the standard dia was changed to be the max (+) diameter acceptable tolerance.

At the same time the standard bolt race diameter was changed to be the minimum (-), and the max (+) was changed to be the standard diameter.


This is supposed to be the reason why pre-1916 SMLE actions were preferred as the donors for the Australian HT program during WW2 (because they are toleranced tighter, not because they "Flexed better").