Real Guns Barrel Burner Index:
  Case Capacity - grains
  Bullet Diameter - inches  
  Max PSI
  257 Wby Mag 270 Win 30-06 300 WSM 375 H&H
Diameter: .257 .270 .300 .308 .375
Index: 20.9 15.7 13.3 16.8 15.7
After years of flame cutting barrels through use, it became obvious that there was some relationship between case capacity, bore diameter and gas velocity that dramatically influenced barrel life. So we started tracking barrel dimensional changes over the shooting life of a barrel, or at least degrees of progressive throat erosion, and came up with this formula for placing cartridges into barrel wear and tear context. The same formula also works to gauge cartridge efficiency, the velocity return on powder charges.