Another reality check re: burn rate

[ric426]

Just checking to see if my thinking is correct.
From looking at various load data I get the impression that, in general, for a given bullet weight, case, primer, using the same gun, you'd use less of a faster powder than you would of a slower powder to attain the same velocity.
Is that correct or am I over simplifying it?

 

[ants]

Pretty much correct.

If you look at a curve of pressure vs. distance travelled in the bore, you would find approximately the same area under the curve for the same muzzle velocity, but the curve is skewed closer toward the chamber for faster powders. Nevertheless, both powders burn really really fast. Most of the work is done before the bullet is half way down the pipe. The two curves are surprisingly close together.