other than pure lead?

Hello. I did an internet search on this and didn't find the answer so I thought I would ask. I have always "known" only pure lead was to be used for muzzleloader projectiles, and sort of assumed it was because pure lead expanded more easily and that conicals needed to be soft to engrave on the rifling but thinking about it lately, I want more information. Can anyone give me information on the use of "soft" lead alloys used for muzzleloader conicals? Thanks, Kurt.

slow twist, 1 in 48 say pure works fine , as does 1 to 20 tin and lead. Faster twists sometimes need harder bullets, but 1 to 20 usually works

Jerry, thank you for the reply. After I posted I did find I could buy bullets cast with the 1:20 hardness. I still wonder about harder bullets and wonder if "upset" or the, upon firing, combination of bullet compression and expansion factoring into bullet hardness with muzzleloaders? My question is inspired by one of Idaho Lewis's videos in which he shows his loading procedure. Posted below and at 2:00 of the video he shows loading one of his pure lead bullets and pushing it into the muzzle of his rifle with his fingers. This bullet is obviously not engraving on the rifling at loading but most likely engages the rifling coming out. Pressure undoubtedly does that and perhaps would not with say, a wheel weight bullet. I don't know?
https://youtu.be/gkqhDg1c78w

I shoot long range traditional ML so was interested to learn about what was originally used for bullets in the first Creedmoor matches between the Irish and American teams as well as the rematch held in Ireland. The Irish team used muzzleloading rifles exclusively where as the US team used cartridge rifles specially made for the event. The information I found stated that a slightly hardened alloy was used . The 45 caliber ML Rigby rifles used had 1/18" twist rates which is what my Billinghurst 45 caliber rifle uses. I get very good results with a slightly hardened alloy of about 50-1. I feel that a 20-1 alloy may be too hard for muzzleloading rifles using bore diameter bullets . A 20-1 alloy in cartridge rifles is pretty much the norm but those rifles are shooting bullets at groove diameter or slightly over in the same calibers.

I'm no expert for sure but my experience is that if you shoot a hot enough load copper jacketed pistol bullets and 45-70 bullets and various bore riding copper and jacketed lead mz bullets work fine. The scoop I've heard is that the bullets "obturate" or swell to block the bore and expand into the grooves as the hot gas from the charge reaches the base. I believe the softer the alloy of the bullet the less gas and pressure is needed to obturate. I also think softer bullets don't behave well at higher pressures and velocity as they can melt. With the jacketed bullets I can shoot them in my Rice and GM LRH renegade barrels at extremely high velocity for a sidelock and I believe they are capable of sub MOA but that would take "optics" with my old eyes. I can manage 2" occasionally with a peap and post though.

So the way I figure it, your alloy choice depends on how hard you want to push the bullet and what you want it do at impact. If you want high velocity shoot a hard alloy and a bunch of powder. If you want less velocity shoot less powder. You still have to shoot a bullet at the proper rpm range to stabilize it obviously though. So I guess if you want a lighter bullet for caliber use harder alloy and more powder and vs versa for bigger slower bullets. Now an old school round groove barrel with deep grooves is still gonna need some kind of patch to obturate it.

I have found that if you use enough powder you can size even a jacketed bullet so you can seat it with very light pressure and it will still shoot great. I am not afraid of substitutes and use BH209 and T7 with jacketed bullets. But I bet the principles still apply with BP too.