Things warp when they change temperature.
Things like, say, rifle barrels, which warp at different rates than wooden stocks.
When it's cold out (like, say-- 38 degrees), the difference between the inside of a rifle barrel and the outside (except where the barrel is shrouded in wood) is more pronounced.
This interferes with accuracy.
This REALLY interferes with accuracy when the barrel in question is extremely lightweight, and the temperature rises quickly.
From, say, a significant centerfire cartridge like the .30-'06.
Now-- let's say that you pick up the rifle for the first time in years, and go to qualify with it, and discover that it's 2.5" left and an inch lower than you wanted at 100 yards? Why, you'd take the extra cartridges that you brought, and sight it in, wouldn't you?
First two shots-- cover with a dime. Next shots-- cover with a quarter. At 6 shots-- cover with a silver dollar. At 10 shots-- cover with, oh... a dollar bill. Gawd.
While waiting for the too-hot-to-touch barrel to cool, the rangemaster said to me: "I gotta close up in 15 minutes."
So I qualified with 20 rounds in 15 minutes. It wasn't pretty. 10 rounds at 100 yards, and 10 rounds from 50. Even with a superb rest or a rock-solid prone, my rounds at this point weren't going too terribly closely to where I wanted them to. Sure, the Ruger M77 super lightweight contour barreled rifle topped with an older Redfield scope may not be the choice of snipers everywhere, but this one is actually capable of some pretty decent cold-barrel groups. Unfortunately, that requires a degree of slow fire that I just didn't have the luxury to enjoy today.
The targets were various tombstones of 2 to 4 inches in height. Should have been a snap. I think I missed black on 4 or 5. I've got it in the car, enshrouded in shame. I'm not sure I can bring myself to turn it in.
Oh, the shame!