I think what he means is that the cylinder/chambers were fouled from firing the shorter 22 LR cartridges. Scrubbing with a copper/bronze brush would clean them up good as new. In theory, you could burn a ring into the cylinder/chamber by firing the shorter 22 LR cartridges, but I think that you'd have to fire thousands of 22 LRs in a 22 Magnum chamber to do any damage to a firearm with any quality.
Other than making a dirty chamber, the only real problem with firing 22 LR in a 22 Magnum chamber is that the cartridge isn't supported properly, since it is a smaller diameter case, and the bullet can't be centered in the chamber, so it will hit the rifling at an angle. If you use a chamber adapter, such as those sold by Ace Dube, the 22 LR cartridge is properly supported and centered, so the bullets hit the rifling straight and go pretty much where you're aiming.
Jeff
