What you refer to as the National Defense Manual is actually called a CFTO:
Canadian Forces Technical Order
The C3A1 CFTO is: C-71-234-000/MA-000 - this is the first book
MA - Data summary
MB - Operating instructions
MD - Equipment description
MM - 1st line maintenance instructions
MN - 2nd/3rd line maintenance instructions
MX - Illistrated repair parts manual and scale
MY - Parts identification list
The C3A1 barrels never ever had front sight bracket holes drilled. The rifle was never ever designed with iron sights in mind - period! If you have a barrel with the holes, you have a C3 barrel. The above tech drawing is a mishmash of several diagrams. That is an M87 stock, iron sight C3 style barrel and a Canadian C3A1 action body.
I'll have to scan my C3A1 parts diagrams to give you the true parts look. I don't have a scanner so it might be a while. Maybe I can snap a picture of the page. It doesn't have the screw holes you refer to. Maybe you're looking at a C3 CFTO, which did have the bracket holes.
Also, here's a tidbit of info probably most people won't know unless they were a tech - there were 2 lengths of barrel available - 24 & 26" as well as 3 twist rates 1:10, 1:12, 1:14. This all depended on what nato stock # you used to order.
Don't ask me why it was like this - only the LCMM(Life cycle material manager) can answer that. Most techs I knew were not shooters or collector's either. I happen to be one of the exceptions within the trade.
The overall weight of the rifle with the scope was: 15.875 lbs - say 16 pounds for ease of remembering. The rifles weight is on par with what the M40A3 weighs(17 lbs).
I don't want to sound rude or come off as condesending, so please take this with the spirit with which it is intended


- but if you've never worked with this rifle and only have used a book to give an educated guess - please don't offer advice, because you'll only confuse people searching for the correct answers. I'm not the end all answerer to this rifle, I just happen to know what I know from years of using and maintaining this rifle!
All the best, Carl