All around rifle?

[Basement-Gunsmith-Z]

At 500 yards any ar should do fine. The only time that an ar isn't reliable is when it hasn't been cleaned for a long time. The m1a soccom is quite heavy, and won't he as maneuverable as an ar15. I actually use an ar at 1000 yards.
Plus, .223 is a Lot cheaper than .308.

 

[emcon5]

Something like this:

http://www.gunbroker.com/Auction/ViewItem.aspx?Item=300441840

Light, compact, and with bullet selection/availability to take anything in North America from ground squirrels to elk.