Investarms made a 58 cal.It had a 1-48 twist.It was also sold as Cabella's brand hawken.

I hunt with a homemade hawkin style .58. I bought a 36 inch green mountain barrel cut it back to 32 inches and and installed it. I also installed a L&R hawkin flintlock. It is my favorite hunting rifle. I shoot 90gr of GOEX 3f behind a pillow tick patch and round ball(285gr)greased with bear grease. This combo has never failed me. I have taken many deer and a few wild hogs with this load.

As mentioned before though, a 1-70 twist is strictly a round ball twist. Also, Green Mountain barrels are threaded at the breach for a breachplug but not furnished. They are excellent barrels.