hot water down the barrel is to remove any corrosive residue from any old ammo that may have been put through the gun. most regular solvents and cleaners won't remove this. you only need to do this after shooting corrosive ammo and it wouldn't be a bad idea right off the bat since you never know. the only other thing is "sticky bolt syndrome"
check this out
http://www.surplusrifle.com/shooting...esbs/index.asp
surplusrifle.com is a great resource