Modern gunpowder efficiency

[Roboss]

Some time ago I read about modern gunpowder being only 30 percent efficient and the rest simply exits the barrel or something along those lines. Is it true? If so could you provide details. Not even sure where I read it anymore

Also what is the highest velocity that a modern gunpowder.could propell a bullet at?

 

[mcb]

Some time ago I read about modern gunpowder being only 30 percent efficient and the rest simply exits the barrel or something along those lines. Is it true? If so could you provide details. Not even sure where I read it anymore

Also what is the highest velocity that a modern gunpowder.could propell a bullet at?

30% is about right. The rest of the chemical energy goes into accelerate the gases themselves, heating the gases, the bullet, the barrel, etc. A good bit of that energy is used to overcome friction in its various forms. Friction of bullet on barrel, friction of gases in the barrel. Friction of air in front of the bullet in the barrel, etc. Some of the energy goes into vibrations of the gun parts and the air both in the audible range and outside of that.

A cool feature of Quickload software is that it give you a fairly accurate calculation of what percentage of the original chemical energy in the propellant gets converted to kinetic energy of the bullet.

As for your last question I will point you to a recent, very long and somewhat contentious, thread where the forum discusses what limits the maximum velocity a gun powder propelled bullet.

https://www.thehighroad.org/index.php?threads/speed-of-chemical-propellants.868474/

 

[Roboss]

30% is about right. The rest of the chemical energy goes into accelerate the gases themselves, heating the gases, the bullet, the barrel, etc. A good bit of that energy is used to overcome friction in its various forms. Friction of bullet on barrel, friction of gases in the barrel. Friction of air in front of the bullet in the barrel, etc. Some of the energy goes into vibrations of the gun parts and the air both in the audible range and outside of that.

A cool feature of Quickload software is that it give you a fairly accurate calculation of what percentage of the original chemical energy in the propellant gets converted to kinetic energy of the bullet.

As for your last question I will point you to a recent, very long and somewhat contentious, thread where the forum discusses what limits the maximum velocity a gun powder propelled bullet.

https://www.thehighroad.org/index.php?threads/speed-of-chemical-propellants.868474/

Funny thing is I created that thread. So asking the question was kind of stupid.

 

[Walkalong]

Some time ago I read about modern gunpowder being only 30 percent efficient and the rest simply exits the barrel or something along those lines. Is it true?

Not even remotely.

Oops..."efficient", yea, don't know the numbers, but yes, not all of the energy gives velocity.

But 70% doesn't even remotely exit the barrel unburned.

Energy is wasted in almost anything. Motorcycle chains rob energy from the motor on the way to the wheel. Etc, etc.....

 

[roscoe]

Efficiency is only 15-30% in ICE vehicles. I wonder about guns - I would think barrel length might be a factor. These short ARs sure shoot some fire, but in a 24" barrel, much less must be lost to wasted combustion. Heat/friction is another thing entirely.

 

[General Geoff]

Efficiency is only 15-30% in ICE vehicles.

Toyota's latest generation of 4 cylinder engines are actually 40% thermodynamically efficient. Huge deal when that was announced a few years ago. Mazda is currently working toward a 56% efficiency goal with their compression ignition skyactiv-x gasoline engines.

 

[roscoe]

Toyota's latest generation of 4 cylinder engines are actually 40% thermodynamically efficient. Huge deal when that was announced a few years ago. Mazda is currently working toward a 56% efficiency goal with their compression ignition skyactiv-x gasoline engines.

I have occasionally mused about tapping off that wasted engine heat to run a closed-loop steam turbine. You could charge a battery that would work as part of an electric KERS-type system. Probably too heavy and complicated to work, but fun to think about. However . . . not gun related.

 

[748]

We know the muzzel energy, to include recoil and bullet rotational energy.
How do we get total lower heating value of a certain propellant?
Then all we would have to do is divided the 2 numbers then we could know precisely what goes where.

 

[Zaydok Allen]

This is a question where the answer could easily be misinterpreted.

When I hear efficiency I have the same initial reaction Walkalong had, thinking completion of powder burn. If talking about how much energy actually gets applied to accelerating the bullet, 30% seems logical when you consider all the things that the chemical energy gets applied to when firing a gun. So mcb's explanation seems correct.

We need to make sure to keep the two concepts separate.

 

[roscoe]

I assume you could calculate caloric energy in the dry powder (by burning it), then compare that to the velocity x mass of the slug.

 

[mcb]

I assume you could calculate caloric energy in the dry powder (by burning it), then compare that to the velocity x mass of the slug.

This is basically what Quickload software does. The energy density of the propellant is know and is one of many parameter for in propellant in the programs database. When you put a load into the program and it runs the internal ballistics simulation and it knows how much energy it started with and compares that to how much kinetic energy the projectile leaves the barrel with. That ratio is you efficiency.

 

[buck460XVR]

This is basically what Quickload software does. The energy density of the propellant is know and is one of many parameter for in propellant in the programs database. When you put a load into the program and it runs the internal ballistics simulation and it knows how much energy it started with and compares that to how much kinetic energy the projectile leaves the barrel with. That ratio is you efficiency.

This reminds me of a discussion had with a fellow reloader in a gun shop recently. We were talking about Quikload(he had just obtained this for himself) and other available software out there and came to the conclusion that at some point the technology/software will be out there and the database available so that one could determine the most efficient powder and charge, for any particular bullet, out of any particular barrel length, with any certain barrel twist and trying to obtain any particular velocity. It's already close. The came the discussion on what one would then have to talk about on internet gun forums........

 

[denton]

When the bullet uncorks the barrel, the energy stored in the compressed gas is lost to propulsion. Shorter barrels suffer a greater loss, and are less efficient.

The friction of the bullet in the barrel for jacketed rifle rounds is typically around 150 pounds. By work/energy, that puts the friction loss at around 300 ft-lbs.

 

[mcb]

This reminds me of a discussion had with a fellow reloader in a gun shop recently. We were talking about Quikload(he had just obtained this for himself) and other available software out there and came to the conclusion that at some point the technology/software will be out there and the database available so that one could determine the most efficient powder and charge, for any particular bullet, out of any particular barrel length, with any certain barrel twist and trying to obtain any particular velocity. It's already close. The came the discussion on what one would then have to talk about on internet gun forums........

Quickload does have a system that does help you optimize load but it take a fair but of work on you part and some undestanding of what exactly the programe is doing. But you can specify a few parameters and it will try every propellant in its database that meets you selection criteria and show you the results.

For example you can select a particular cartridge and bullet and barrel length. You then give it a maximum pressure and min and max case fill (it will allow compressed loads to some degree). It will then simulate every power in it database and give you a list of propellants with the charge weights that meet you pressure and case fill limits. The output includes case fill percentage, velocity, percent burn, peak and muzzle exit pressures and time in barrel.

You could also specify a specific velocity you want and it will give you all the loads that can reach that velocity (though many will be over-pressure, but it warns you about those)

There are several other combination of parameters you can select to help select a load that does what you want.

 

[buck460XVR]

Quickload does have a system that does help you optimize load but it take a fair but of work on you part and some undestanding of what exactly the programe is doing. But you can specify a few parameters and it will try every propellant in its database that meets you selection criteria and show you the results.

Yes, I know. What we talked about was a program where all you had to enter was caliber, bullet weight, barrel length, twist rate and desired velocity, and the program would spit out a specific powder and charge weight. Similar to how some load manuals have their recommended loads, but using more variables than just their test platform and narrowing it down to a smaller range powder charge using one powder for your parameters. For instance, I have 686s with 3", 4", 5" and 6" barrels. I could ask for a specific recipe for each to give me an approximate start point for a specific bullet weight to obtain the same velocity. This would give me similar POI from POA at various distances with all 4 guns. Is this something important for the majority of handloaders? No more so than Quickload software is, IMHO, or even a chrono. But for some folks it may be an important tool or just something fun to play with for ships and giggles. The real just of my previous post was the statement......"Then came the discussion on what one would then have to talk about on internet gun/reloading forums........"