I was told when I started shooting my 338LM, that barrel life would be 1500-2000 rounds, MAX. I found my barrel was at its best at about 3000 rounds, but that could also be because I had learned how to handle the rifle then ;)
Viht N570 is a double based powder, and I have been told that it eats the barrels faster than a single based powder, but I have no indication that this is the truth.
I can no longer see the lands in my barrel, teh grooves are gone, you can see them abot an inch from where the riflings should start, and still I get very nice groups. I tell myself that it is because of the long barrel that this is possible. I likie to think that even though the bullets gets a rough start, it will settle during the long barrel time, and be ok when it leaves. I have no other explanation to it. If you look inside my barrel, you would say it is worn out, but, no.
This is a 10 shot group I shot this winter when the barrel had 3000 rounds through it. Used 250 grs Scenar bullets, and the range was 600 yards.
I do not think I will ever repeat this one.