BlkWtr,
Once upon on time, on a now comatose board (shooters.com) a gent who, if I recall correctly, writes ballistics programs stated that a one grain weight variance with the typical BP cart bullet (500 grs) will only change the velocity about one FPS. "One grain=1FPS" is an easy way to remember it.
Not much to fuss about. Now if you are going to mix a bunch of bullets together that vary more than that say 5 grs or more in variance then there may be some stringing vertically at the longer shooting distances.
Then again, a heavier bullet would come out at a lower vel, which may mean more barrel jump before the bullet exits the bore... but to further confuse things I suppose the jump depends on the rifles configuration and the mass (resistance to recoil) etc of the shooter attached to the rifle.
Ain't this fun?
Hoppy
P.S. I can still access the archives at shooters.com but the only thing that shows up when I open that site is a post from mid January.... something about a 30" barrel. It appears that is when posting stopped. Is that what you people get.... or is something amiss with my system here?