There is ancedotal evidence that some high energy powders in overbore capacity cases will cause shortened barrel life. But Varget is not one of those. I use it exclusively on one of my 6mmBR rifles with a Bartlien competition barrel. Over 1300 rounds so far, and I have not had to chase the lands yet. That load in a 22-250 will not eat the barrel until you get up above 2500 rounds.
This is just foolish...
It is so common that hotter powders in overbore capacities shorten barrel life that it cannot be denied by anyone today. Varget is Hodgdon's hottest rifle powder, and a 22-250 ain't exactly underbore.. It holds more powder than a 6br, and it's bore is smaller. What do you think the results of this are?
As mentioned, heat is the big factor here. Well heat is energy, and different powders release different energy per mass. They also release the energy over a different area within a given bore diameter. If the bore is smaller, or powder is faster/pressure is higher, that energy is applied to a smaller area. If you don't allow that energy to travel away from that area before re-applying more, your barrel will suffer the consequences of this. Oh, and while you're doing this, the barrel seems cool overall -because you haven't let the heat travel away from it's offending point.. USE A TIMER
A friend of mine recently shot out a 25-06 before he was through with it, because he laid down 3sht groups with it constantly(fantastic groups). He never thought he was hurting the bore because at his 3sht limit he could wipe the back of his hand down the barrel without burning. So he got his best groups shooting fast from a warmed up barrel, that he didn't allow to get 'too warm'.
Well now he can get to the back of a few lines and hope to finish another barrel that shoots as well as that one had, with a new load that he'll have to find.
This was a nice hunting gun with ~1000rnds, and he could have used it for 5 lifetimes if he had let it cool a minute between shots.
Barrel life goes;
1. shot timing
2. powder amount per bore area
3. powder heat
4. pressure
5. carbon constriction
Barrels don't ever, ever wear out from bullet friction..
The only coating I'm aware of known to 'potentially' increase barrel life, is moly. This, only because it reduces flame HEAT as it vaporizes. It also extends the bore area remaining heat is applied to. But as most folks have come to realize, moly can also reduce barrel life, if not removed consistently enough to prevent a moly ring from forming.
This is similar to the ultimate killer of barrels, #5