As you increase the bore size the more powder that is able to burn before it will damage the bore becasue it has more room to expand and does not enter the throat at such a high velocity and temperature as it does in smaller bore diameters.

It also has a lot to do with the bullet weights. As you increase bullet weight the powders burn rate needs to be slower in order to generate acceptable velocities in a given case size. So since the powder is burning slower it isn't getting as hot as quick and the burned gasses are not traveling down the bore as quick and eroding the metal.

Still alot of it has to do with the way you shoot it while practicing. If you keep firing round after round and the barrel gets so hot that it will burn your hands then you will wear out any barrel quickly. If you take a shot or two and let the barrel cool then it will last you considerably longer. Remember that the hotter the steel gets the softer it gets and the easier it becomes to erode it away.



The .338 bore diameter won't be bad and should keep good hunting accuracy for several thousand rounds but the .375 bore will be even better.