I've gotten good service from CastPerformance, which would probably be immediately available. The bullet I've used is the 420 grain LBT GC, .459".
My preference is Beartooth Bullets, specifically the Piledriver Jr, .460", but you'll have to wait on that one for a couple of months, that company always has a wait time, but it's a good product.
I've run these bullets from 1635 to 1800 fps in my Guide gun, but in reality, the higher velocities are not needed for bullet performance on-game, but I've tried them faster for trajectory reasons. My shoulder says "No need".
Those two bullets will kill anything around here at 1300 fps.
