Have a new MPA Custom Match Rifle coming in 6GT, want to start loading new brass.

[Jhoman]

I have all my dies & new Alpha 6GT brass & Berger 6mm 105 hybrid target bullets. Wanting to load the first 100 rounds to be ready to fire form the cases, when the rifle arrives. I have Varget, StaBall 6.5, and IMR 4350. Would you just load them all with the same powder and load them towards the starting loads or break them up and try all three powders? Also would you suggest loading them at the min COAL of 2.515 not knowing the rifle's chamber? These will be just to break in the barrel & fire form the brass!