I've used RE-19 for several years in my Remington 260 Mountain Rifle. I've gotten good accuracy with it in my hunting rifle. I shoot a 140 grain Sierra SPBT with 44.0 grains and a Hornady 129 grain SST with 46.0 grains. I've not checked the loads across a chrono, but I can tell from the recoil from other loads that my RE-19 loads kick harder.
I have a couple of loading data sources which list loads for 140 grain bullets from starting loads of 40.0 grains to a maximum of 45.0 grains. The Speer #13 manual lists RE-19 as the highest velocities with their 120 and 140 grain bullets.
RE-19 may be temperature sensitive so, be mindful of that.
I haven't switched to the 260 in a L/R rifle, I still have 3 - 308 L/R rifles that have a lot of life left in them, but I do like the 260 for hunting. I've taken a few Deer a pig or two and an Antelope with it. It has worked as well as my old 270 does.
