A couple of things:
I've burned out more than one 30-06 barrel, but I shoot a lot: a 30-06 721 I have is on it's 4th barrel. It has been my experience. that carbon build up will more likely affect accuracy than copper build up, but that being said. If you're going to clean the barrel clean it well, before giving up on it.
I'd try:
JB Bore cleaner on a tight patch around a bronze brush.
Then I'd use a foaming cleaner until the patches have nothing but blue on them.
Then I'd clean with an oil based ammonia cleaner or any ammonia cleaner if you are going to stick with it until clean. One often recommend is Montana extreme, though the smell is poignant, will clean the barrel well after the carbon is out. There are several different ammonia cleaners and I use three or four (Butch's, Sweets, Montana Extreme, & ?). So far I don't see much difference in their performance. If you use an oil based ammonia cleaner you don't need to worry about leaving it in the barrel, evidently. If I stop cleaning a barrel for say a period of time such as an hour or more (sometimes I don't know when I'll be back to cleaning it), I put a couple of patches of oil down the barrel.
When I cleaned my rifle barrels in preparation for Dyna Bore treatment, I was surprised how much copper I had removed out of some rifle barrels that shot well (and thus I didn't worry about cleaning).
Finally any 700 barrel will fit a 721 action. A new take off 30-06 700 barrel can be found for $50.
The 30-06 with premium bullets will be good for anything on this side of the world. Unless you want something different stay with the 30-06. It certainly would be one of the two cartridges I'd consider if I were only to have one rifle for game. The 280 would be on that list too, maybe even the gay cartridge, which I will not mention - reputation, you know.
