Have a Lyman Great Plains Rifle with a 32" 1 in 60 twist, sidelock percussion. I just bought a Mag-Spark 209 conversion nipple for it and will be trying FF Pyro RS and FF T7 (what I have on hand). Will be getting some Blackhorn 209 later also... I know it'll shoot round balls just fine but I'd also like to shoot Lee REALS and wanted to get anyones experience with those in this rifles twist. They offer them in 300 and 380 grain molds. I figure the 300s would behave better in 1-60 than the 380s since "the heavier the bullet, the faster twist rate needed". Am I correct in that thinking? Any and all input appreciated.

Not gonna happen, at least not accurately.

If you want a 209/conical/sabot shooter, sell that off and get one. What you have ain't that.

Nah. I dont want and never have wanted a centerfire bolt, break or lever rifle you happen to reload by the muzzle, instead of on a bench. Imho that's just not in the spirit of what "primitive" season is or what it was started for (iron sights, sidelock, no sabot). I like Colorados' view on it. I can buy a 1 in 32 barrel then run the heavy REALS and conicals, but tiny budget prohibits that. Just needed experienced advise before I experimented and bought a mold. (live on tiny VA) I bought the rifle from a friend for a very good price and didn't have the option of ordering one with the hunter barrel. I have no probs with RB's, they kill deer, elk, etc the same as any other chunk of lead. The Mag-Spark is a common sense reliability upgrade as around here there is no real black powder, rare #11's, and sidelock natural hard ignition.

It's not the heavier the bullet, it's the longer the bullet the faster the twist required.

My experience trying to shoot conicals out of a 1 in 60 is that they are not very accurate, although, you should try them and see if it's "accurate enough" for your purposes.

I suggest you buy or cast some REALS and see what results you get. I've shot them out of an old TC Renegade, but that was 1 in 48 twist. They worked fine, plenty accurate to kill a deer or elk at 100 yards or so.

You might get by with the Hornady PA conical or its sire, the Buffalo Ball-et, both of which are little longer than a RB at about 230 grains,(50 cal).

BH209, besides a hot spark, also requires a tight-fitting projectile for proper ignition and burn. The maker specifically recommends against traditional conicals. I tried a PA conical in my Knight and it blooped out of the barrel like a champagne cork.

Yep, I'd try Ball-et or PA conicals.
I shoot patched ball in a 1/28 with very light loads just to practice. Heavier loads won't stabilize. I imagine the patch strips from the rifling. Generally slow twist is deeper for patches, and faster twist is shallower.

I've got everyone at camp shooting R.E.A.L bullets. In fact these were what got me into bullet casting. Always try the shortest bullet available in a roundball gun first.

My son is shooting them in a 50 cal Lyman Hawken and has no problems with accuracy. I've been shooting them in a 54 TC Hawken for about a decade.