My old Speer manual states that Rugers 45-70's are 1 in 20". Whether that holds true for the Lyman rifles, I don't know. To be honest I have one and have never bothered to measure it.
Use the tight patch/marked rod method. This will give you a very close approximation.
I get lots of sideways looks when I tell people I got 2750 fps in the 28" barrel with one of these with 300 Hornady Hollow points. The 350 gr. got 2700 fps. They where very accurate in my rifle. I shouldn't have sold it, so can't check the twist, use the method described by gewehrfreund. The new Leverevolution bullets should work too.
Mine is also an overrun rifle (not many of those around!) and it only came with the long Lyman scope, which someone must have robbed from one of the sets.
A previous owner had an extra set of scope base holes D&Td around 3-4" in front of the rear factory drilled holes (i.e. at the same distance as found on most factory 1Vs. Two rear 1V bases work perfectly to allow mounting a modern scope
Most likely one of the many etched versions that always seem to be for sale on the internet, but never seem to sell :roll: . Or was it in fact one of the very rare unmarked overrun rifles?
Did not look at it that closely and was passing thru town. Was in the "gun room" there and was too expensive for this cheapskate to ask to look at> Think $1,000+