Any of you guys cast conicals from a Lyman mould and shoot them in a .50 muzzleloader? How do they shoot, and is it worth pursuing as a viable hunting bullet, if cast from pure lead, or maybe 1:40 or so?

Slug your bore and take into account the twist rate of your barrel. Which Lyman and what rifle/model? Heck yes, conicals are most definitely worth pursuing as a hunting bullet.

White .50s, one Super 91 and one 97 Ultra Mag, both with a 1-in 24 twist... so which Lyman mould do I buy?

I'm not sure you should buy a Lyman at all. Go to MountainMolds armed with some mold specs from Batchief or Super91 (Bob Bowers). Bob actually designed a bullet for the .504 Whites that shoots GREAT and is called the N.E.W. . I'm sure they would be glad to share the mold's design specs. I will ask them to email you the info (hope the one in your profile is correct).

Lyman did make a mould, the 512138 that would surely have made a good bullet. The bullet from that mould would likely size down to a usable .504 in pure lead.

That Rapine mould below comes with handles, the MtnMolds do not but you can grind a bit off a Lyman handle and it will work.

If you want a ready-made you might look at this one http://www.buffaloarms.com/browse.cfm/4,2228.htm

I try never to miss a chance to show this PICTURE Those bullets hit like Thor's hammer and are VERY effective as hunting bullets. Most shown are .451 cals but the .504s are just as convincing.

For $17.95, including handles, I purchased a Lee REAL bullet mold that throws a 320 gr. pure lead conical in 50 cal. I shoot it in two different muzzle loaders. One has a 1:32 twist and one has a 1:28 twist, both work well for me.

Roger, I cast Lee REALs also but they just don't usually work so well in a fast twist White.

The Lee 457-405F casts a great bullet that shoots remarkably well in the .451 Whites after sizing. A few of the groups in that pic I linked were made with that $13 Lee mold. Sure have nothing against Lee molds but wish they would offer something more modern for the .50 muzzleloaders. I've suggested that to them more than once. That same .457-405F style in about a 507-450 would be great.

Little brother 457-340F does right fair in a Knight Elite .45