I think the macro mechanics of it are pretty simple. Hot gasses at high speed erode the throat through the combined effects of burning away some of the metal and scouring. (If you have ever seen a valve body steam cut due to a gasket leak it isn't hard to imagine). The barrel is more subject to damage from the gasses if it is already heated. More powder makes more gas, generates more heat, and for a given bore size moves at higher velocity. Managing those effects will go a long way towards preserving barrel life. Allow time between shots for the barrel to cool. Use moderate loads. Use heavy for caliber bullets - the gas can only move down the bore as fast as the bullet lets it.
The change in barrel life observed by 83cj-7 when he switched to a slower burning powder I think might be explained by a change in the bullet acceleration rate immediately after ignition and perhaps a lower peak throat temperature. That suggests using the slowest burning powder that gives the desired performance is also beneficial.
