Rifle Barrel Heat Generation Analysis


What causes your rifle barrel to heat up? Is it the burning gun powder, or friction between the bullet and bore? What happens to the energy released from the smokeless powder when you fire your rifle? I recently asked these questions, and my 'cronies' at the AllOutDoors Coffee Shop had the right answer regarding the primary cause of barrel heating. Most of us just 'knew' the answer but couldn't prove it. One fellow had the proof (thanks again, Robert). From the analysis, about 3/4 of the barrel heat is from the burning gas, while the remaining 1/4 is due to bullet/barrel friction.


Analysis

I knew I read about this before in Hatchers notebook. According to tests done at Springfield Armory in the .30-06 Browning machine gun the breakdown was as follows:

ENERGY CONSUMED IN FIRING
EventCaloriesPercent
heat to cartridge case 131.0 calories 4.26 %
kinetic energy of bullet 885.3 calories 28.78 %
kinetic energy of gases 569.1 calories 18.50 %
heat to barrel 679.9 calories 22.10 %
heat to gases 598.6 calories 19.46 %
heat generated by friction 212.0 calories 6.89 %
Total 3075.9 calories

They used IMR4895 in the .30-06, and all IMR single base powders have the same energy content and flame temperature. Using a different powder such as a double base or on with a different energy content/flame temperature will change results slightly. By the way, as shown above, only about 30.9% of the powders' potential (chemical) energy is converted to the projectile (kinetic) energy.


A separate answer, which I found much later, is below:

In a series of tests, the Brits determined approximately how much (%) of the energy in a powder charge went to producing the several results of firing the cartridge. (Note that these are typical, approximations, and certainly variable to come extent from one cartridge and load to another - not rigid, not exactly the same for all loads.)

ENERGY CONSUMED IN FIRING
EventPercent
firearm recoil 0.1 %
heating the chamber and barrel 25.7 %
barrel friction 3.5 %
moving powder gas to muzzle 3.5 %
muzzle blast 31.8 %
heating the bullet 3.5 %
spinning the bullet 0.5 %
propelling the bullet 31.4 %

I hope this write-up proves useful to you. Good shooting from the Spirit of '76 Gun Page!!


Last updated : 21 April 2000

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