I've tried both balls and conicals in a Remington 1858 and didn't have a great deal of success with the conicals to be honest.
As far as the sprue cut off is concerned, I don't have any, as I roll my balls, first between two, faced blocks of steel, then on a piece of tuffened glass, finishing of with the base of a pellet tin on the glass. End result, a very round smooth and shiney ball. I know it's a lot of messing about, but I've got first place in my league two seasons running since I started doing this, so I think it's worth rolling your balls
ATB
Baz
Toys : .308 Rem 700 SPS Tac, 7.5x55 Schmidt Rubin K31, 7.62x54R Mosin Nagant M44, .45/70 Browning Mod 1885 HWTR, 8x60R Portuguese Kropatscheck, .58cal PH 1861 Enfield Carbine, .22LR-CZ452 Silhouette Tac, .22LR Smith & Wesson-M&P 15-22-M4 Carbine