I don't have any info with Rel 23 so I'm giving you what I have. Safe in my 6.5.x 06 , with E.R. Shaw stainless 24" bbl, 1/8 twist. I just worked this up yesterday on my home range. 51.5 grs IMR-4350 with the 121 gr Hammer bullet.
Tiny three shot groups. Hope this is helpful. 54 grs of Rel 26 with the Nosler 140gr AB gave me 3075 fps.with no excessive pressure signs & also tiny groups.