Factory loaded jacketed bullets of modern manufacture,  will be perfectly fine in your carbine.   These are  loaded for use in a Colt SA and the 1873 model Winchester.  If the bore is a bit rough, I would clean it up with a mag tube full of factory jackets.  It won’t  hurt the gun and will probably clean up some of the questionable areas.  After that, I use a hard cast lead.  Hard cast is less apt to lead up the bore.

 Under the heading of this is what I do, cast not sized in the original Winchester 44WCF mold. I use wheel weight lead, dropped out of the mold into a bucket of water. They measure about .429 with some areas a little smaller and hand lube.The bullets shoot accurately and work in all bores with rifling. The rounded corners on the bullet size to the bore upon firing. I have used the original molds on all my 73’s,76’s, and 86’s. The Winchester molds were designed for their guns and shipped without a sizing die, I use it that way. They are available on EBAY for $100 or so, small price compared to the cost of jacketed bullets. Jacketed are nice to clean an old rough bore, but it has been my experience no more accurate than cast not sized. If you size the bullet you have to match it to the rifle, not sized ammo goes in a wider range of bore sizes. That old steel mold can make a nice bullet!  T/R

Rick,

Not sure about the hardness of the bullets used in Winchester Cowboy loads, but my guess they are hard.  Most companies loading lead for the cowboy action shoots, do use hard lead.  I think they do this, because a lot of guys are using old guns and some with rough bores.  A soft lead bullet will lead up a bad bore in no time.

According to the reproduction 1896 Winchester catalogue I have, the original 44 WCF bullets were pure lead. I use pure wheel weights, air cooled, to give a soft-cast bullet, not quite as soft as pure lead. Water dropping them will give you a hard cast bullet which work for a lot of people, but they always give me leading. Congratulations on acquiring that SRC.