I have a 22-250 Ackley Improved, Tikka Action, Border stainless barrel in a Mcmillan stock. I use it with mainly 75grain A-max (38.5grains Vit 160 at @3200 fps) there are no pressure signs and I don't consider this to be a hot load.
The rifle has has 450 rounds through it and the barrel is allowed to cool between shot strings. I have noticed that the oal has moved forwards 25 thou since I last checked it when it was new.
Is this normal wear?

Yes this is normal, the price for speed. Don't you love speed!

Erosion is not wear.The problem of "erosion" has been carefully studied and it is not erosion ( which means wearing away). What happens is that the steel gets very hot from the hot gases and absorbs carbon form those gases.This changes the composition of the steel and causes cracking, then further deterioration. To minimize the problem use less powder and take time between each shot to cool the barrel.

If you shoot the fast ones, the throat will gradually look like a snakeskin and accuracy will decline, often going to a heavier bullet will pick it back up, but it's only temporary. I haven't had much of a problem getting .220 Swift barrels to last 3000 rounds however.

Thanks gents, I was surprised at the erosion as I am using heavy bullets travelling relatively (for the calibre) slowly.

Andy Mass:

I shot a 22PPC in competition where I would shoot 10 to 15 rounds in 7 or 10 minute periods. The barrel was then cleaned and cooled. I found I had to chase the seating depth every 250 rounds or so to the tune of .005. I had access to a quality bore scope. At that time a couple of my friends were playing with 22 Ackelys and 22 Cheetahs. It was obvious with the bore scope that the bigger cases(greater volume of gases) eroded more quickly. Other variables that we found were the type of powder and the lots of barrel steel. We watched for but could never find that shoulder angles, at least from 30d to 40d changed the erosion rate. The analogy that was given to me was that the throat area was much like putting a cutting torch on steel. The smaller the hole the quicker it eroded. It was probably the result of quicker gas flow at a given volume through the smaller hole. The 22's defintely eroded faster than larger calibers. The higher the pressure the more quickly the throat eroded. But they all did it. Even with the same size cases. It is possible that the longer bearing surface of those 75 gr bullets might be coppering the barrel quickly and causing it to heat quicker than with shorter bullets. A shorter shooting string between cleanings might help slow the erosion.

knobmtn