My procedure for magnum loads is to cast WW and water drop them. I then size and lube them through the RCBS lubrisizer with 50/50 Beeswax/Alox lube. My final step is to tumble lube them With the lee liquid alox. It sounds to me like your leading was caused by not enough lube and a new (rough) bore as others have mentioned above. I have been able to push plain base Keith style bullets at 1400+ fps with the above technique in revolvers and rifles with little or no leading with this techique.