Yes, so the big aperture bit of this footage has been used in an earlier Extra Vid. But what are these Extra Vids for, if not for re-cycling footage to illustrate specific points? In this case, that the Lee-Enfield No.4 big aperture isn't less accurate than the small aperture to any meaningful degree. If you understand this and concentrate!
Here's the Canadian 1945 manual referred to: https://drive.google.com/open?id=1i-5B_VJTdzbGVBBNbBV9ASvsMMw1Znza
.303 British sights smle
Firearms history, blokesplaining firearms mechanics, mythbusting, shooting sports and kitschy sketches all in one place. An often dry and sarcastic look at whatever takes the Bloke's and the Chap's fancy in the world of guns and shooting.