Oh, my!
The man knew what he was doing, that's certain.
Hew was building a Number 4 action into a SERIOUS match rifle. Notice the official Canadian "SALE" marking and the CAL rollmark.
Plugging off the mag well and welding in a permanent insert stiffens the action so that it better tolerates the twisting from the higher-pressure 7.62 NATO loads. It also allows you to use a solid-bottom stock which gives greater rigidity to the wood and less problems in bedding the thing. Open rail under the barrel is for an adjustable sling, can also be used for weights for offhand shooting.
You see, I know HOW to do all these things and WHY to do them, I just DON'T do them!
This would be an awful monster to carry around, but I'm not gonna stand in front of it and stick my tongue out at half a mile, either!
Complete his work, friend, and you will have one FORMIDABLE range rifle.
What year is the action?
.