Somebody mentioned it earlier but thought I would just add, the Ruger polymer mags work great...
I don't live in the arctic anymore & I don't know how they would hold up to -40 celsius... But if it's that cold, watch out for your trigger guard too. (I would love to see a metal replacement)
Here's what I have found with my Ruger and the metal vs Polymer mags.
Metal : They rattle in the magwell a LITTLE bit, cannot be loaded through the bolt (have to load rounds by sliding them in when the mag is out of the rifle), they get REALLY COLD when the temp drops below freezing - so the way I hold my rifle on the stock/mag when shooting I better have mits on. They run the rounds when cycling BEAUTIFULLY.
Polymer: Perfect fit in the magwell - no movement, fit snug, NICE. The polymers I can load right through the bolt by just pressing the rounds down - its a bit tight (they are no lee enfields for top loading - but they work). In the cold - NO problems at all - comfortable to hold, not cold at all, BEAUTIFUL. Rarely but occasionally when cycling the rounds - a round gets fussy and can hang - need a tiny bit more bolt push to make the round move right - may just be a 'work in over time' thing - is it a huge problem ?… not for me. I run the metal when its warm & the Polymer in the cold.
OH…. and th polymers are shorter than the metal mags (see pictures)
Metal 10 rnd- 9cm from stock
Polymer 10 rnd- 7cm from stock
Picture of the mags beside each other - plus a metal 5 rounder (for size comparison).
(for those who read the WHOLE thread…the metal 10 round mags will actually take 13 rounds, polymer only 10).