There are four modern configurations, 18¾" Talo Trapper w/sights ~.840" muzzle, 22" standard Handi w/sights ~.800 muzzle, 24" Stainless no sights ~.800" muzzle, and 32" Buffalo Classic, dovetailed front sight, it's .840" at 22" for comparison, all are drilled and tapped for a scope rail. H&R centerfire rifle barrels are 4140 alloy, so any of the 45-70 barrels will handle smokeless pressures, the Handi is chambered in 500S&W which has a SAAMI MAP of 60kpsi, H&R 45-70s work fine at modern rifle pressure levels.
Tim