I know of many people who use the 7.62x39mm round for deer, bobcats varmints etc. And .223 is one of the most popular varmint rounds there is.

Dont forget that the .30-06 was developed as a military round and it's Soviet counterpart, the 7.62x54R, is used just as widely for hunting in Siberia as the 'Aught Six' is used in the U.S., often in WWII era Mosin-Nagant 91/30's or M38's which are one of the most accurate rifles ever made (See: Stalingrad & Vasili Zaitsev). The problem most people have with military arms is thier excessive weight, and that's why most are 'sporterized' (Known as Bubba-ized in the gun collecting community) by shortening the barrel, replacing the wood for plastic, and tapping scope-mount holes in the receiver. This completely destroys the gun's value, but if you dont give a rat's ass and just want to have something to kill Bambi with, go ahead.

In my honest opinion, an AK-47 fitted with a 4x scope, a longer stock, and with the legal capacity magazine, would make a kick-ass brush gun for anything deer-sized and smaller. Plus, if you dropped it off a cliff, the cost of replacement would be less than the cost of repair on something like a Weatherby or Beretta.