This is my response to your question in the MilSig contest thread.
Originally Posted by Shocker_Monkey
The smaller paint should be okay in the mag. Although be careful if you're using mag pouches as the smaller paint won't be held back as well by the mag collar.
No, using different paint wouldn't be necessary.
And yes, magfed is fine in the winter. Just look at all the Canadians playing magfed at CQB in the middle of winter (Plenty of youtube videos at CQB).