OK.. Started with 69 grs of Rel 33. 24" Bbl 1/8 twist Very mild... Worked up to 75 grs which produced 3455 fps with the 121gr Hammer . Easy extraction without the slightest sign of pressure. 74grs showed 3419 fps. Decided to stay with the 74 gr load. Started with two new cases. Fired a total of 14 rounds ( 7 times each case ) working up the load & shooting targets. Primer pockets stayed snug/tight. Target, 4 shots at 108 yds. At 235 yds on my range . shot almost as tight. To much snow to slog threw for me to use my 522 td range. My test tell me Rel 33 is a fantastic powder with the 264 mag. Retumbo , I have found to be be the fastest acceptable. H-1000 to fast with any bullet heavier than 100 gr in the 264. Rel 26 although a good powder is to fast for this size of case