Never really tought of Santa as an AK kind of guy...more an H&K or Sig.
No way. Look, it's 2006 and this guy is still using a magical sleigh and eight tiny reindeer. He's no more going to replace his trusty muzzle-loader with an assault rifle than he's going to replace Rudolph with a Surefire.
One thing's for sure - any guns of Santa's are of 18th century design (or earlier), but possess magical abilities. I'm guessing they magically, instantly reload themselves, perhaps with a magical gun-dust more potent and efficient than any black-powder south of the pole. And I should add that Santa is an old, old guy with loads of free-time in the off-season. If he enjoys shooting at all, he's sure to be a crack shot.
The question is, what sort of muzzle-loader is he packin'?