The project’s goals as stated in the presentation were to eliminate the need for spare barrels to be carried by reducing barrel temperature (especially chamber temperature) and increasing the cook off limit of the barrel (the point at which a barrel gets so hot that rounds will fire from heat alone, without the primer being struck by the firing pin), without a decrease in accuracy or an increase in barrel weight. The team investigated two different 3D printing methods for manufacturing advanced barrel units: [Bold added: SiG]
When heat is dumped into anything, there are only three ways to get rid of it:
- Conduction is by far the best way to get heat out of a system. Examples are things that have been bolted to the hot object to carry heat away. Forced water jacketed cooling is by conduction.
- Convection is generally a distant second. Something like a computer CPU that has a heat sink on it, but no fan, is depending on the heat causing air currents across the heat sink to carry the heat away. The heat sink just increases the amount of surface area that forces the air currents. Forced air cooling, blowing a fan across that heat sink, is more like conduction cooling.
- Radiation - radiating the heat away by infrared radiation - is not usually a factor, although it can be when the temperature is very high. When a barrel (or anything) is glowing red hot it's loosing lots of heat by radiation.
- Cobalt Superalloy Liner – we know these are good with respect to wear, also play some role in minimizing heat into the barrel
- High Strength Core – minimize the thickness and weight of core
- High Heat Capacity Jacket – maximize volume/mass –Reduces overall temperature increase per unit of heat into the barrel
- Optimize outer profile of barrel for increased convection