If you know any or all of this, please ignore me . . .
I have a lot of 5 and 6 cavity aluminum rifle molds, on Lee blocks as well as others. I do find I need a bit more Tin than the same type of mold with pistol bullets, and I need to run my Lee furnace at maximum. I cast using scrap Lead/Antimony/Tin wheelweights, with a bit more Tin. If I don't add some Tin and run hot, I have a problem with laps where the metal splashes on mold filling. I don't care if my bullets are frosted.
Handling all the bullets is a problem. I almost always drop them into a 5-gallon bucket of water, which keeps the bullets from dinging each other.
I usually run with a Lee 20 pound furnace to cast from and a Lee 10 pound to act as a melter. While the furnaces are doing the initial melt, I have the mold sitting on top to preheat. I usually have Lyman ingots sitting on top of both furnaces preheating as I cast.
It is necessary to lubricate the Aluminum molds or you will get galling, an adhesive wear mechanism. I really like Bullplate, but #0 pencil graphite rubbed on the mold top, sprue plate bottom and locating pins will do some good. Bullplate is available through the Cast Boolits board.
http://castboolits.gunloads.com/showthread.php?t=3412