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# Barrel length and powder burn rates?

#15
05-31-2009, 10:51 PM
 Platinum Member Join Date: Oct 2005 Location: Michigan Posts: 2,232
Re: Barrel length and powder burn rates?

Quote:
 Originally Posted by su37 "Absolutely not true, if they burned in the first 2", then why would you see fire out the end of a 20" barrel with slow powder?" Your seeing gases re-ignite when they leave the barrel and hit oxygen. ALL POWDERS BURN WITHIN THE FIRST TWO INCHES OF BARREL LENGTH AND NO MORE! If you think that slow powders burn all the way down a long barrel you are mistaken. Quick Load shows us slow powders that create a different pressure curve than faster powders. Longer barrels create longer pressure times.

If all the combustion was done at 2" and the max pressure was the same, then the pressure curve would be the same for all powders. The pressure would drop as a direct relationship to the increase in the interior space created within the barrel as the bullet moved forward. All powder would have the same pressure curve if it had the same maximum pressure.

However, since some powders burn SLOWER than others, the continued combustion continues to fill the space created by the bullet as it moves forward.

Here are some graphs from Quickload. Using a 300WSM and 3 different powders (H110, H4350 and H50BMG), a fast powder, a medium powder and a SLOW powder; I've graphed the combustion percentage over the barrel length.

If you trust Quickload, you can clearly see that combustion continues as the bullet moves down the barrel. With the H110, combustion is complete in about 5", about 20" with H4350 and with H50BMG it never completes.

H110 combustion graph.

H4350 combustion graph.

H50BMG combustion graph.

This is why it is so important to match projectile weight, barrel length and powder speed.

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

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#16
05-31-2009, 10:56 PM
 Platinum Member Join Date: Jul 2004 Location: Texas Posts: 7,232
Re: Barrel length and powder burn rates?

Quote:
 Originally Posted by su37 "Absolutely not true, if they burned in the first 2", then why would you see fire out the end of a 20" barrel with slow powder?" Your seeing gases re-ignite when they leave the barrel and hit oxygen. ALL POWDERS BURN WITHIN THE FIRST TWO INCHES OF BARREL LENGTH AND NO MORE! If you think that slow powders burn all the way down a long barrel you are mistaken. Quick Load shows us slow powders that create a different pressure curve than faster powders. Longer barrels create longer pressure times.
Say WHUT?

All gun powders have there own oxygen supply and don't need the outside air to burn or they
wouldn't work at all.

And if they all burned in the first 2 " then we wouldn't need but one kind of powder.

Most powder are of the same chemistry but granule size and coatings determine the burn rate.

I think you miss quoted/worded your post .

Not trying to pick a fight just trying to keep others out of trouble.

J E CUSTOM
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#17
06-01-2009, 01:18 AM
 Silver Member Join Date: Jul 2001 Location: San Antonio, Texas Posts: 244
Re: Barrel length and powder burn rates?

Quote:
 Originally Posted by AJ Peacock If all the combustion was done at 2" and the max pressure was the same, then the pressure curve would be the same for all powders. The pressure would drop as a direct relationship to the increase in the interior space created within the barrel as the bullet moved forward. All powder would have the same pressure curve if it had the same maximum pressure. However, since some powders burn SLOWER than others, the continued combustion continues to fill the space created by the bullet as it moves forward. Here are some graphs from Quickload. Using a 300WSM and 3 different powders (H110, H4350 and H50BMG), a fast powder, a medium powder and a SLOW powder; I've graphed the combustion percentage over the barrel length. If you trust Quickload, you can clearly see that combustion continues as the bullet moves down the barrel. With the H110, combustion is complete in about 5", about 20" with H4350 and with H50BMG it never completes. H110 combustion graph. H4350 combustion graph. H50BMG combustion graph. This is why it is so important to match projectile weight, barrel length and powder speed. AJ
Man! You guys had better start giving instructions on how to find stuff like this. It took me the better part of 15 min to figure out where go to change the graph inputs from those that are on the Icons at the top.

I didn't even know you could do that! You got anymore little tricks up your sleeve?

I am very impressed with Quickload. It was well worth the money! Can't wait till I figure out how to use half of the functions, or rather figure out what those functions are.
#18
06-01-2009, 04:38 AM
 Platinum Member Join Date: Oct 2005 Location: Michigan Posts: 2,232
Re: Barrel length and powder burn rates?

Quote:
 Originally Posted by steve smith Man! You guys had better start giving instructions on how to find stuff like this. It took me the better part of 15 min to figure out where go to change the graph inputs from those that are on the Icons at the top. I didn't even know you could do that! You got anymore little tricks up your sleeve? I am very impressed with Quickload. It was well worth the money! Can't wait till I figure out how to use half of the functions, or rather figure out what those functions are.
Sure, there are all kind of little tricks. But it's gonna cost you to find out

I'm sure you know the following 'ease of use tricks', but I'll list them just in case.

1) copy powders file to a file named AccessiblePowders. Then edit that file with a text editor to remove all the powders you would never use/ could never find. Then select that file, so all your output is limited to just those powders you would be interested in. Also, create another file that contains only the powders you have on YOUR shelf (call this one "On-The-Shelf" or something similar).
2) Make a bullet file for each bullet diameter.
3) Make a Cartridges file that only contains your rifles (customize the water capacities etc. for the brass YOU use).
4) You can edit your new Cartridges file (created in #3 above) to add wildcat cartridges. Just use a text editor and fool around with the entries. You can start with a standard cartridge by creating the entry by saving it from the Quickload user interface, then edit it. For example, open the .308 Win in the normal cartridges file, then switch to your file and save the cartridge
(selecting "data: Add, Change, Load, Save"->"Case/Caliber"->"Change Data in Active File"). Then edit the entry in your text editor (ie. change the name, H2O capacity, groove diameter etc etc). I do this for each of my cartridges/case lots, so I don't have to repeatedly edit the overall length, H2O capacity etc.
5)
__________________
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
#19
06-01-2009, 08:58 AM
 Platinum Member Join Date: Aug 2005 Location: Murray, Ky. Posts: 1,411
Re: Barrel length and powder burn rates?

Quote:
 Originally Posted by bookworm Hi Nathan - actually it is helpful to me. Do you happen to know the barrel length of your buddies rifle?

Hey man sorry about the delay, his barrel is 26".

Nathan
#20
06-01-2009, 09:05 AM
 Silver Member Join Date: Jan 2006 Posts: 375
Re: Barrel length and powder burn rates?

Well as a matter of fact, I don't trust Quick Load. It may get you on the right track but I don't put what it says in the bank.

I'll say it again,

The ball of flame is the hot gas from the powder reigniting when it hits the oxygen of the atmosphere, not still-burning powder.

Almost all the smokeless powder in a charge, say 99% plus, is consumed within at most a few inches of the case mouth, and often a lot sooner.

Of course the load has to create about the right pressure for the powder, as various powders are designed to burn best at different pressures. When the pressure is low for the powder then many powder granules simply won't burn. A few stay in the bore, but most are blown out the muzzle--but they aren't burning.
#21
06-01-2009, 11:05 AM
 Platinum Member Join Date: Oct 2005 Location: Michigan Posts: 2,232
Re: Barrel length and powder burn rates?

Quote:
 Originally Posted by su37 Well as a matter of fact, I don't trust Quick Load. It may get you on the right track but I don't put what it says in the bank. I'll say it again, The ball of flame is the hot gas from the powder reigniting when it hits the oxygen of the atmosphere, not still-burning powder. Almost all the smokeless powder in a charge, say 99% plus, is consumed within at most a few inches of the case mouth, and often a lot sooner. Of course the load has to create about the right pressure for the powder, as various powders are designed to burn best at different pressures. When the pressure is low for the powder then many powder granules simply won't burn. A few stay in the bore, but most are blown out the muzzle--but they aren't burning.

Why don't the gases "re-ignite" when you use a faster powder then?

If all powders burn by the time a bullet moves 2" down the bore, please explain how (from a physics standpoint) slower powders maintain higher pressure longer than faster pressures. Remember, as the bullet moves down the bore, the volume inside the combustion chamber grows. If the combustion was complete, pressure would drop in direct proportion to the change in the volume behind the bullet. This would mean that we would only need a single powder for everything?

You may not trust Quickload and it's data, here is a quotation from a book on Gunpowder that you can consider as well.

Gunpowder: Alchemy, Bombards, & Pyrotechnics by Jack Kelly - ISBN 0-465-03718-6

"Smokeless powder burns only on the surfaces of the granules. Larger granules burn more slowly, and the burn rate is further controlled by flame-deterrent coatings which retard burning slightly. The intent is to regulate the burn rate so that a more or less constant pressure is exerted on the propelled projectile as long as it is in the barrel so as to obtain the highest velocity."

I read this to mean that the powder continues to burn as the projectile moves down the barrel, this maintains pressure to create more velocity.

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

Last edited by AJ Peacock; 06-01-2009 at 11:09 AM.

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