Pressure v. Velocity

[Jim Watson]

If it is hard to tell Clays, International Clays, and Universal Clays apart, how about those colored "Dot" powders? And why can't I use 4895 instead of 4831? They are only 64 apart and that isn't much out of four thousand.

And try not to think about the actual factory, the vendors will cheerfully contract powder from someplace else and put the same label on it. Close enough.

 

[denton]

Maybe a couple of graphs will help....


Here is the pressure vs. time curve for H110 in a 6" 41 Magnum. Note that the pressure peaks at about .25 milliseconds, and that when the bullet exits the muzzle, the gas pressure is 8589 PSI. Because so much of the energy in the compressed gas is lost when the bullet uncorks the barrel, efficiency is only 21.6%



This is what a load with about the same peak pressure looks like with Universal. As others have noted, the load uses a bunch less powder. The pressure peaks earlier, and when the bullet exits, propellant gas pressure is 4392 PSI. Because less propellant energy is lost at bullet exit, efficiency is higher.

Without launching into a discussion of integral calculus, the force on the back of the bullet at any instant is proportional to the gas pressure at that instant. Higher pressure for a longer time = more muzzle velocity. You can see that H110 provides more pressure for a longer time, even though peak pressures are about equal. This is the important point. Efficiency and pressure at bullet exit are side notes.

CAVEAT: This data is from a QuickLoad, which is a MATHEMATICAL APPROXIMATION. Do not use this data for real world loads.

 

[jski]

Maybe a couple of graphs will help....

View attachment 1102969
Here is the pressure vs. time curve for H110 in a 6" 41 Magnum. Note that the pressure peaks at about .25 milliseconds, and that when the bullet exits the muzzle, the gas pressure is somewhere around 7500 PSI. Because so much of the energy in the compressed gas is lost when the bullet uncorks the barrel, efficiency is only 21.6%

View attachment 1102970

This is what a load with about the same peak pressure looks like with Universal. As others have noted, the load uses a bunch less powder. The pressure peaks earlier, and when the bullet exits, propellant gas pressure is closer to 5000 PSI. Because less propellant energy is lost at bullet exit, efficiency is higher.

Without launching into a discussion of integral calculus, the force on the back of the bullet at any instant is proportional to the gas pressure at that instant. Higher pressure for a longer time = more muzzle velocity. You can see that H110 provides more pressure for a longer time, even though peak pressures are about equal. This is the important point. Efficiency and pressure at bullet exit are side notes.

CAVEAT: This data is from a QuickLoad, which is a MATHEMATICAL APPROXIMATION. Do not use this data for real world loads.

Excellent analysis!