I loaded 8 x 60 for some years with lead bullets: smokless, black, hard lead, soft lead. I got one superb group at 100yds with all 5 bullets touching: the rest were rubbish. The original bullet was lead wrapped in copper foil! I suggest that you try standard 8mm Mauser jacketed. bullets.
Fred.

i once owned an 8mm x 60mm Krop rifle(which used the same ammo).The barrels on these measure about .330, so .323 bullets don't shoot well in them, i used pulled Jacketed bullets from 8m x 56R Hung. ammo for the M95 Steyr rifles, they shot fine with a case full of FFG Black powder, i don't rebember the load, the rifle was stolen in 1983, a long time ago. I believe this surplus ammo can still be optained, also i believe RCBS makesa bullet .330 dia for this rifle, but i don't rebember the number, however there is an article on shooting this rifle in 1993 
Gun Digest if you can buy one on the EBay they are cheap(not the ammo, the Gun digests)

I have been using these in my Guedes with very consistent groups. (You need to Login or Register to view media files and links)

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Jerry I realize that since that is how Western lists it.  While it is 42 grains lighter than the original Guedes MilSpec load, it is about as close as one can come with the commercial casters I'm familiar with.  While I cast for a number of rounds, I don't cast for them all and have been very pleased with Western's products and service.