Link to the mod?Cold by itself is a total non-issue. I havent hunted with the oem ctr mags, but running them in matches in the snow have never had any failure—although thats not much of a test. Regardless, if the mag is good in general I wouldnt worry too much about running it in winter, just carry a spare and if you have an issue swap mags like any other gun, and put the problem one inside your jacket to thaw so you can clear it.
In general, independent of any conditions some people have failure to feed issues with ctr mags—seems to be dependent on the infividual mag. Out of my 4 mags I had one problem mag. Pulling the base plate and bending the spring fixed it. Theres a good youtube vid on how to do this.
I used shooter71’s bottom metal modification so my ctr bm would accept either ctr or aics mags, and used the MDT flush 3-round mags for hunting (with a little modification).