Shooting rimfire in the cold

At minus 20 I find that CCI Standard Velocity drops about 2 inches more at 100 yards than in warmer weather. I don't know if it's the powder being cold, or the cold air being denser than the warm air.
Denis
 
There's a simple reason why any .22LR ammo "drops" more when it's cooler. MVs decrease as temps fall and increase as temps warm.

Why? The "explosion" that propels the bullet toward target is the result of a chemical reaction. The rate of chemical reactions is temperature dependent, more energetic when it's warmer than when it's cooler.
 
Maybe 'single-load' with extras in your shirt pocket . . . and after a few rounds to 'warm up the barrel' ? I did 'OK' last week with mags kept there @ -10C but only at 25y and 50y - and not particularly accurate rifles anyway. A Sav-64 w-red-dot and Stevens 66 with irons. And both are awkward to 'single-load' with cold fingers.
 
I have no real experience, only what I've seen shooting a couple of matches. The carbon barrels tend to hold velocity better, as well as accuracy, when it's cold. Maybe it has to do with the cold contracting the barrels making the bore tighter?
Anyone have any other, and better experience with this?
 
Thinking more about this, the barrel bore shouldn't shrink on contraction with the cold, I'd will grow, od will shrink. Not matter how miniscule, dealing with 0.001" tolerances that jam up up, it will most definitely be a factor as well. How much of one, I'm not sure.
 
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