Don't know about the High Walls, but Brian Pearce has written that the only Eyetalian Sharps he trusts with smokeless are the Pedersolis. He looks into this stuff a good bit, being a fan of lever guns, single shots and single actions. You might try to contact him about it, but my guess would be "no" as to strength. Not sure about the design. Some of the nice American replicas are direct copies I think, but I've never seen them offered for modern rounds. The Mirokus have been all along.
