I know this answer doesn't directly relate to the question but..... The original spec for the No4T was that it should conform in every respect to the standard service rifle which they did. But as soon as the standard of the standard service rifle started to deteriorate (?), such as two groove barrels, mazakbutt plate, solid foresight block bands and any other relaxations in standard you may care to name, then what? Each and every one of these 'relaxations in standards' was tested, sanctioned and approved by the Ordnance Board. So while the standards were relaxed, the rifle remained 'standard'
And at BSA, all they were interested in was X amount of 'standard of the day' rifles that had passed a higher than the laid down accuracy criteria ready for conversion to sniper rifles. In fact we now know that there were some 2 groove No4T's although post war we would always rebarrel with 5 groove 'new' barrels. I can't speak for Canadaor 4 or 6 groovers but to have been fitted, they WILL have been approved by the Ordnance Board and become a standard, albeit for the period of the war.