While it is not a Ruger, I have been out on a qualification course at about 0 degrees and ran quite a few rounds through my Glock 21. Never a problem. In fact, in extremely frigid weather, I find that the poly framed guns are easier to shoot than metal framed guns- the poly frame won't transmit that bone-numbing cold into your hand like a metal frame will. Shoot with confidence, your poly framed gun will hold up FAR longer than you will and at far colder temps.
Bub