every now and again we see old packets of long range match ammo which contain bullets of 12:1 alloy.
current belief seems to be that 16:1 is as hard as you can go.
an interest in history overcame fear of leading and other unknowns, causing 12:1 to be tried today.
no dirt diggers, at 300 meters.
in fact the best average vert ever was observed.
the ODGs might have used these alloys for a reason.
keep safe,
bruce.