powder charge vs bullet weight....

[quiknot]

either i seem to be misunderstanding this concept or......

looking at my reloading data / recipes..as the bullet weight goes up, the powder charge seems to decrease....seems to me that with a heavier bullet you would need a larger charge of powder to push the object out of the barrel....

tell me more....

 

[WayneConrad]

I think it goes like this:

As the powder burns, it expands. As the bullet moves, the volume that the hot gasses can expand into increases. Pressure is a function of how much gas there is vs. how much volume the gas is in.

A heavy bullet moves slower (inertia, f=ma and all that), so the volume increases slower. The same amount of gas now has less volume to expand into, so pressure increases. Now the amount of powder must be decreased so there will be less gas generated, otherwise you'll have overpressure and possibly a very bad day.

I think.

 

[dakotasin]

yeah, its a pressure game. nothing more. heavier bullets develop more pressure.

pressure is neither good nor bad, it just is. and you have to work within the limits.

 

[Crosshair]

This is why you see heavier charges with slower powders when using heavy bullets. The slower powder gives the bullet more time to move.