slick, sorry, I started out to answer your first question and got to jabbin over developing the load. Too fast lead in the barrel can do several things, including making a horrible cleaning job. Bullets can 'strip the rifling' causing very poor accuracy to include problems such as key holing. Sometimes they seem to shoot just fine, but just make large groups. As far as velocity, the best thing to do is use a chrony. Things like bullet size, type and amount of lube, velocity and powder burn rate (pressure curve) have direct affect.
Also made an error in previous post, the size of my 7mm cast bullets is just barely over .285 after sizing/lubing.
Good luck on your project! sundog