I tried I-7828 and Retumbo and settled on Retumbo.
I use a 300 grain Berger Hybrid OTM Tactical #33794, and load it up with 89.5 grains of Retumbo. I use Winchester Large Rifle Magnum primers, and I am getting 2780 FPS. I am getting 1/2 to 1 MOA groups (which is about all I am capable of-the gun can do better).
Gun is an inexpensive Savage 110BA with a 26 inch barrel, and 1:9 twist.
You may want to play with your Overall Length to tune your load once you find a powder charge you like. Extending or retracting your OAL may tighten up your group a little