Should be able to get 1,300fps to 1,350fps with BP and that heavy a slug. 545gr. is 1.2457 ounces.(437.5gr. per)

Might take the full case of powder - assuming 2 3/4" hull. A 3" hull would be easier, of course.

If nitro proofed, very easy, even in a 2 1/2" case, I'd think.

good luck