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# Barrel length and powder burn rates?

#29
06-01-2009, 11:10 PM
 Platinum Member Join Date: Jul 2004 Location: Texas Posts: 6,872
Re: Barrel length and powder burn rates?

AJ.

You are a silver tongued devil and I don't think It could be explained any better than
you did.

The only thing I can add to your explanation is that in addition to needing one kind of
powder we only need 2 inch barrels.

Don't give up though, the world really is flat !!!.

J E CUSTOM
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"PRESS ON"
#30
06-02-2009, 03:12 AM
 Platinum Member Join Date: Oct 2005 Location: Michigan Posts: 2,232
Re: Barrel length and powder burn rates?

Quote:
 Originally Posted by J E Custom AJ. ... Don't give up though, the world really is flat !!!. J E CUSTOM

Thanks JE,

This says it better than I can.

What we have here is a failure to communicate.

AJ
__________________
If some is good and more is better, then too much is just right.

My mind is a raging torrent, flooded with rivulets of thought, cascading into a waterfall of creative alternatives
#31
06-02-2009, 04:06 AM
 Silver Member Join Date: Jul 2001 Location: San Antonio, Texas Posts: 244
Re: Barrel length and powder burn rates?

SU37

I think maybe you missunderstood what you have been told. You were probably told that most cartridges burn "most" of their powder charge in the first two inches of barrel.

All I can say is "Go take a thermodynamics class".

You will find that you cannot possibly make all powders to burn at the same rate (all burning within the first 2" of barrel), generate the same chamber pressure, and yet produce different volumes of gases. In order to maintain higher pressures for longer periods of time, as the volume increases, combustion must continue for longer periods of time. Here's were the Thermo class will come in real handy, take a specific mass of gas and compress it into the volume behind the bullet at 2" down the barrel, then release it. The drop in pressure is directly proportional to the increase in volume. So, if what you're saying is true then I could take any powder and load it to a max chamber pressure of 60Kpsi and I will achieve the exact same velocity for a given projectile in a given length barrel. Which I believe that even you will agree is simply not true!

As for different powders generating different pressure curves, you are right. They do! But, you can't have a different pressure curve when all powders complete combustion in the first two inches. Again "take a Thermodynamics class". The pressure curves are almost identical at the begining, but the difference in velocity is in the fact that higher pressures are maintained further down the barrel with slower powders, ie higher velocity.

Now as for the powder gases reacting with the atmospheric air. Well, you must first understand that all smokeless powders contain (in chemical form, as in within each molecule) enough O2 to achieve complete combustion. You can take a sample of any smokeless powder in an environment divoid of O2 and yet it will still burn to completion. If you don't think this is possible then I suggest that you go take a "Chemistry class". There are numerous substances that do not require an outside source of O2 in order for combustion to occur, nor do they require a flame or spark. At a given temperature and pressure, auto-ignition will occur.

Not to be condesending but you might try educating your self before you try to use what someone, anyone else tells you. Just because a Hodgdon or Ramshot employee (didn't feel like explaning how things really work or didn't know any better), tells you that all powder is burned in the first two inches, doesn't mean that that is how things really are. If you think so, then BOY DO I HAVE A DEAL FOR YOU. See I just happen to have some ocean front property in Arizona, thats got your name writen all over it!
#32
06-02-2009, 04:15 AM
 Silver Member Join Date: Jul 2001 Location: San Antonio, Texas Posts: 244
Re: Barrel length and powder burn rates?

OH! AJ

"A failure to comunicate"

Now that is exactly what we've got here!

Now that's funny ****! HAHAAAAAAAAAAAAAAAAAAAAAAAAAAA

Sorry, It took me a minute to stop laughing!
#33
06-02-2009, 04:49 AM
 Platinum Member Join Date: Feb 2008 Location: IOWA Posts: 1,995
Re: Barrel length and powder burn rates?

su37,
I am surprised you are stating your position based on what one person told you over the phone. I would think it would be prudent to keep an open mind and research this, gathering imformation from many sources. Then make up your own mind based on your own research. You have been given alot of valuable imformation in this post from some very experienced shooters that have been there done that. The only way to continue to learn is to be flexible and willing to change as new imformation is learned.
#34
06-02-2009, 11:13 AM
 Silver Member Join Date: Jan 2006 Posts: 364
Re: Barrel length and powder burn rates?

"su37,
I am surprised you are stating your position based on what one person told you over the phone."

Where did I say i took a position based on one phone call?

"keep an open mind and research this"

That's exactly what I'm trying to do! And I do appreciate the other posters viewpoints.
And er, uh, maybe ya 'll need to open your minds. lol!

Messenger boy here, don't kill the messenger!

From friend, ballistician, chemistry major and very well known writer. His email answer to me,
one of many from labs which pretty much all said the same.

"They don't all burn up within 2". The peak of the pressure curve will vary, say from 1/2" in front of the chamber in a .45 ACP with 10 grains of a very fast-burning powder to maybe 3-4" in something like a .30-378 with 100+ of very slow powder. But the powder does essentially all burn up just in front of the case. The peak of the pressure curve is where it is all burned up.

....with a couple of caveats. The peak pressure developed must be in the range that the powder's designed for. For instance, IMR4895 works very well in the .45-70 at low pressures for trapdoor Springfield loads, but in that case it's only developing 25,000 psi, not the 50,000 psi IMR4895 is designed to burn at most effectively. But the powder doesn't keep burning on down the bore. Some of it simply doesn't burn, and if you place a sheet on the ground in front of the rifle you'll find unburned powder granules all over the place.

Even at the correct pressure a tiny bit of powder doesn't burn, 1% or less. But again, it simply isn't going to burn. All the powder that WILL burn is burned up just in front of the chamber.

So no, different powders don't ALL burn up within the exact same distance in front of the case. The cartridge, powder, bullet all have an effect, and the point of peak pressure does vary. But the powder doesn't keep burning on down the bore. The gas created keeps expanding.

All of this was proven many years ago by Homer Powley during his work at goverment arsenals."
#35
06-02-2009, 11:19 AM
 Platinum Member Join Date: Oct 2005 Location: Michigan Posts: 2,232
Re: Barrel length and powder burn rates?

I think we have a classic mis-communication.

Su37, are you talking about where the physical powder charge is when it is burned?

I've been talking about where the bullet is when the powder is completely burned.

I have no idea where the powder is when it is burned..

AJ
__________________
If some is good and more is better, then too much is just right.

My mind is a raging torrent, flooded with rivulets of thought, cascading into a waterfall of creative alternatives

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