26 isn't that stable as far as I can see but it seems to give bigger velocities than 4350 or RL23. RL23 is super temp stable. If you're using H4350 now, then RL23 will be your huckleberry. I get exactly the same charge weight between H4350 and RL23 producing exactly the same velocity but I get half the muzzle velocity variation with RL23 that I did with H4350. This is all in ~40gr capacity 6mm chamberings. Takes 39.5gr of H4350 or RL23 to get 2980fps with 115gr DTAC's or 108gr ELD-M's.
Temp sensitivity showed itself too much with H4350 my 6XC so I went back to RL-23 which I'd been using in my .243AI with amazing results. I shoot matches in California desert conditions at pretty small targets and it's always between 60F and 100F. I was seeing too much vertical dispersion when it got hot with H4350, IMR4350 was making too much pressure and was way more unstable and RL23 seems to not care if it's 90F or 50F.