for powder, AA2200. It can also be used in light 223 rounds (55gr and lighter)
available as of now in 8lb jug
https://www.powdervalleyinc.com/product/accurate-2200/
For projectiles, Grafs recently had some .310 projectiles for 24ยข each but they are sold out now.
The total cost will definitely cost more than Tula/Brown Bear etc, but you'll avoid the magnetic ammo restrictions so you can shoot it during the dry season, which is most of the year. As for accuracy, you likely won't see much gains there.