Have successfully used RL26 in two cartridges; 300 WM with a new bullet I can't talk about yet and my wildcat 6.5x57BR (8x57 necked down to 6.5mm and shoulder blown out to 30 deg). Talked to an Alliant tech a few years back. I don't recall the exact conversation but powders like RL16 and 23 are advertised as "world-class stability" and "exceptionally consistent velocities"......."temperature extremes". Where Rl 26, "controlled temperature stability" cannot be advertised the same because it might be or might not be as temp stable as the previous two. It's more cartridge dependent.