I lived for decades in the Far North of Canada, and have known quite a few of the people involved with the Rangers.... both the responsible military people and the civilian Rangers themselves.
There are a few considerations here.
1. The numbers are quite small.... think hundreds, instead of thousands.
2. The issued rifles, #4 Enfields up until the present time, are used by the individuals as REGULAR HUNTING RIFLES, meaning they get slopped around in salt water in the bottoms of boats and kayaks, and used in temperatures running FAR below zero degrees Fahrenheit. They are used on seals, walrus, caribou and polar bears.
3. The rifles are abused so badly that individuals were being issued a #4 EACH YEAR, and the rifle written off (no need to turn it back in).
4. The vast majority of "Rangers" are CIVILIAN native hunters, who mostly live on the land, water, and sea ice and whose military training is extremely rudimentary. Their main purpose as Rangers is simply to keep a watchful eye out for foreign-government activity in very remote areas of Canada's North.
It's a cheap cop-out by the Canadian authorities, to avoid spending REAL money for a formal military operation. Of course, it's serendipity that in this rare case, they actually are using men who really "have a clue" about their areas of residence.
With the limited training and unbelievably-harsh environment, I will say that probably NO autoloading rifle would survive for long in the Ranger ranks. The FALs we used in my Canadian Army days worked very well in Arctic conditions, but we were full-time soldiers and received extensive training and lots of practice opportunities in that climate.
