I loaded it with 55 gr. FFFg and a .457" round ball. The thing sure is loud! The ball penetrated 5" into a 6x8.

Oh ... in 3 shots we never had the rammer drop.

mould with a gas check cut ? Cast soft and sans the check it should work as a conical. Might not fit into cut in frame to allow to rotate under rammer but off gun loading always works. .44 special case is about right volume for a 250 to 300 gr.

Reason I suggest a gas check design is the pseudo heel allows you to load it plumb. Hard to get a conical in there straight without heel or tapered diameter.

My walker is currently loaded with a .44 special case of pyrodex p and a r.c.b.s. version of the lyman maxiball muzzleloading conical. No grease in grooves but a smear of soy wax over the top.

but my Dad's home-made "round nose" works pretty well. And I have a mold I am thinking of trying ... casts a 290 gr. for the 480 Achilles ... Heel bullet .. hollow base ... Heel is .452" and if I can size down the nose ......

that lee minie mould for a bullet that you loaded backwards and shot the ram with ?

Should work forwards or backwards.

https://www.americanrifleman.org/content/the-two-sams-walker-colt/