7-300 charge weight

[coyotelite]

I will be receiving my 7-300 this week. I want to run R26. I'm trying to determine my initial charge weight to start load development. I figured there's no info out there that I've found in manuals so how do I go about figuring a safe starting point? I will be running 180 hybrids so I figured a light charge weight for 300 win running 180's would be a starting point but R26 isn't in any of the manuals.