In the late 70's, I had a .58 Hawken built by Taylor, with a Bill Large 1 1/8" straight octagonal barrel. Seems to me, it had a 60" twist rate. I don't remember the groove,vs. land
width, but do recall quite vividly that to shoot 100yards (most of my shooting was at that range in those days), it required 140gr. of 2f GOEX to make it's best accuracy with denim
patched .575's. 1 1/2" for 5 shots was typical. I even shot it with conicals, as I had 3 Lyman moulds, the #577611 which was their thick skirt 560gr., a #574312 OS which I thickened
up the skirts of and cast 480gr. as well as the #57730 with thickened and shortened skirts, cast 675gr. I used those with powder charges up to 160gr. 2F GOEX and got 1,325fps with
the heavy one. These shot almost as well as the round balls, to the 100yard range, but that curved butt plate did a number on my young shoulder. Like a fool, I sold that wonderfully
accurate rifle to a fellow in Terrace, B.C. With less than 140gr. of the then 2F GOEX, it shot 9" and larger at 100yards, but with 140gr., it was a 1 1/2" plinker. Amazingly accurate barrel.