Is the lead keel soft lead or hard alloy? If you have to add tin at $20 a lb in a 10:1 mix it adds $0.18 a pound to your mix to get the same hardness as clip on WW (Brinell 12). I think that it is well worth the price and effort of melting WW to make ingots for casting. WW also have antimony and arsenic which helps if you water drop your bullets, it hardens the bullets allowing heavier loads without undue leading.
I cast pure lead for my .50 and .54 muzzleloaders and I still air cool some WW bullets for my 38 special light target loads but add tin to WW, water drop and use a gas check for my rifle bullets.