I shoot 1000yrd comp here in Australia with 2 distinct cartridges, the 300WM and 338 Edge, in my early days I would chase the lands, to no avail. I would have to start working loads again every time I did this. David Tubb has done several articles on this, as well as barrel contours away from the norm that shoot lights out even though they're lightweight.
Now, I don't even take notice of the amount of erosion, if vertical stringing starts plagueing my groups, I check velocity, if it's dropped, I work back up to the previous known velocity and test for groups. This normally sees me where I was without any tweaking needed.
Now, not to be condescending at all, if your rifle isn't a highly tuned custom gun, then either chasing the lands or my above method may make little difference to your outcome, accuracy will slowly drop off and will never come back. I have had very good accuracy out of a 300 barrel well past 1500 rounds, it all boils down to care and regular cleaning, but not excessive cleaning.