Found an interesting statement in a book presently being read. Thought the topic would generate some interest here in General Discussion on it's merits.

Roger Ford, a well known English author, states in "The World's Greatest Rifles", that the energy of a fired cartridge is spent in the following manner:

1/5 of 0ne percent goes to rotating the bullet

3 percent is accounted for with barrel friction

20 to30 percent is used to propelling the bullet

30 percent goes in heat to the barrel

40 percent is wasted in muzzle blast

He provides no data to support this finding, so I can only repeat it here and see what everyone else thinks.

And here I thought 50% went into hurting my hand/shoulder?

Dan

The problem with things like this is that there is no
place to quit reducing things down.

My physics professor would say that 100% of the
energy eventually gets dissipated as heat.

I certainly don't believe that 30% of all of the energy
is absorbed by the barrel as heat. There simply isn't
enough time for the barrel to absorb that much heat.

I bet it is a much higher percentage that is "wasted"
in the muzzle blast... although "wasted" is a bad term.

What about the percentage that pushes the gun backward?
Or is that absorbed into the figure for pushing the bullet?

I can't find the freak'in heat of combustion for nitrocellulose
online anywhere, and I don't have my Merck index at home.
So I can't do any calculations. Errr!

Dave

Think it's over simplified, but i do think a large percentage is transfered as heat...it takes a good bit of energy to warm up all that barrel steel even a barely noticed 5 degrees. Considering how hot a barrel actually gets after 10 rounds of rapid fire, it is a serious energy drain (someplace in the Physicas book there have to be some BTU experiments).

Know I've read (in some reference book...remembering which one is the trick) some percentages, and heat and noise were to two largest "wastes" of energy. Hard to divorce bullet friction from barrel heating...hard to figure the increased surface area of a rifled barrel (kind of reverse fluting on the inside, but it does serve to increase the surface area inside the barrel) vs. a smoothbore.

But that 30-45% seems about right for a chemical heat engine with a disposable piston (which is as good a description of a rifle as any).

Good comparison with an engine. As the efficiency of an engine depends on bore and stroke ratio, it should be the same in a barrel. As the barrel lengh increases, the loss in exhaust - muzzle blast - decreases, but the friction and thermal absorbtion in the barrel increase too. For those who are fond of mathematics, it would be interesting to compare the data of a round - 44 mag. for example - fired through a short and a long barrel and see how the figures fit with the percentages.

Faber