I have a 30 " Pedersoli 1874 sharps in 45/70 and I purchased a .22 rf liner from a place in Texas. The liner is 24" long and has a 45/70 case soldered to the breach end and drilled so the rf round will fit into it. I think it's a match chamber as it engraves the bullet. There are nodes evenly spaced along the liner and then the whole thing has what looks like some type of shrink wrap over it all. With a little grease on the liner, it slips into the barrel easily, and it works pretty well. I haven't worked with it with the high-cost ammo, but with SK rifle I got around 1.25-1.50" inch groups at 100 yards.
The interesting thing about the whole set up is that it's much quieter shooting, not silencer quiet, but noticeably quieter than my other rimfire rifles. It also verified that my vernier sights were installed correctly. I zeroed the rifle at 50 yards on a large target, and as I moved that target out to 100 yards, I "walked" the rounds up to find my 100-yard setting. The bullet strikes were a vertical line up from 50 to 100 yards. Shooting steel at 250 with the rifle is kind of jaw dropping.
At 10 or 12 pounds, it's not the rifle I'd want to take out into the woods for squirrel hunting, but it always draws a lot of interest at the range. When asked what caliber the rifle is, I tell people it's a 45/70/22.