Synopsis: As was demonstrated in an earlier study, contrary to folklore, barrel heating is chiefly the result of deformation of the steel that results from the rapid rise and fall of pressure within the barrel when one fires a cartridge; hence, the barrel exterior does not continue to get hotter after the shot is fired, as it would if friction and incandescent heating were primary sources of barrel heating. This study irrefutably reinforced that conclusion – in every instance, the barrel cooled continuously after we fired the last shot. What we also proved here was that the efficiency of the chambering, with regard to how much unburned propellant follows the bullet into the bore is a critical factor in overall elastic barrel deformation and heating – more efficient case designs result in less barrel heating (and, likely, these also generate less throat damage) and in less disruption of the shooter's sight picture. This demonstration is of critical significance to varmint hunters (and some types of target shooters) because it demonstrates that performance is not directly related to degree of barrel heating!