Re: 243 ackley
Barrel life is very subjective. Depends on whether the previous owner ever got it hot or not. Was he hot rodding it? or was it a deer hunting gun that he has had for ten years and shot 2-3 boxes of shell before season? Has he changed his seating depth to chase the lands?
All of these things will help determine the present barrel life left.
Overall you should expect a couple of thousand rounds in general if treated right. The 243 AI is a bit of a hot rod and will burn up barrels faster than a 308 for example. In comparision a 308 as a general rule of thumb is good for 10000 rounds. A 6.5-284 is around 1500-2000 so the 243 AI being somewhere in between should be good for 2-5000if not more.
Mike Rock has a 308 barrel with 65,000 rounds down it that just broke 1 MOA, FWIW.
Great cartidge for deer, antelope, coyotes and LR varmints of any kind. I have a couple, but if I had to do it over would do the 243 WSSM now.