Mossy after 3 or so firing of that 300RUM you will find the necks getting brittle and hard. Maybe loss of accuracy too. Maybe split necks too. So to get more life out of the old stuff you can soften up the metal by annealing. Basically heating to a certain temp and dunking in water. But you don't want to heat the shoulders, only the neck. So what vapo was talking about was kinda putting the case in water to the shoulders and heating with a torch. When you reach a certain temp, knock it over in the water.