The only way to run close to 3,000fps with cast, is to use a harden-able alloy and an excellent lube, like LBT Blue.
The old style WW can be oven heated and quenched to reach (after sitting 12 hours) a hardness of up to 34 brinel.
Hard lead shot, having about 5% antimony and also with the requisite arsenic for hardening, can reach very close to this.
For comparison, Linotype is 21/22 and Monotype is about brinel 26.
I have a few lee moulds for .270, however, it would be cheaper for you to buy them locally due to horrific shipping costs from here.