Forget the formula's... When a magnum barrel goes, it'll go all at once. One day it's fine, the next day it's "gone".And that COULD happen in under a 1000 rounds in a barn burner like a 300 RUM.Then again, maybe not...
Personally I don't worry about tube life anymore....I deal with it by ordering barrels way before I need them;have a spare around now so you don't have a 16 week to one year wait when you do need them.Life is simpler that way.
When a magnum barrel goes, it'll go all at once. One day it's fine, the next day it's "gone".And that COULD happen in under a 1000 rounds in a barn burner like a 300 RUM.Then again, maybe not...