Need some tutoring

[kuntao]

Ok I need some help in understanding this concept. It involves chamber pressure and bullet speed. If I take two different powders, one that produces 45000cup and the other producing 47000cup and fire them in the same rifle using the same bullet how is it possible that the lower value cups bullet has a higher velocity? Is it the case that chamber pressure has no relationship to the pressure exerted on the bullet? Presently I feel it does but perhaps I'm totally in left field.
Anyhow any help in giving me some understanding in this matter would be appreciated

 

[stubblejumper]

One load may have a higher peak pressure,but the other load may produce a pressure curve that retains the pressure longer. If you take a vehicle with a 350hp engine and floor the accelerator for three seconds, and then take the same make and model vehicle with a 340hp engine and floor the accelerator for four seconds, which vehicle do you think will reach the higher speed?

 

[kuntao]

One load may have a higher peak pressure,but the other load may produce a pressure curve that retains the pressure longer. If you take a vehicle with a 350hp engine and floor the accelerator for three seconds, and then take the same make and model vehicle with a 340hp engine and floor the accelerator for four seconds, which vehicle do you think will reach the higher speed?

Thanks. That explains it all very clearly. I couldn't find an explaination in anything I read and I spent hours looking. Should have just asked you to begin with!

 

[Ganderite]

Pressure is a curve. Up and then down again. If the pressure drops more slowly, you have more pressure over that part of the curve than the powder that dropped pressure quickly.

Assuming same peak pressure, the powder with the most area under the curve will generate the higher velocity. This would be the slower powder.

Here is a pressure curve for a 308. Note how quickly the pressure dropped. A slower powder would generate higher velocity, but would take up more room and the case was already full.