AJ Peacock
Well-Known Member
"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