You are a brave or foolish man

You certainly have way more recoil tolerance than me, mine tops out with a 416Rigby running 450 grain pills.

I would be zeroing and testing loads off of sticks if you do not have access to a standing support the likes of Rigby etc use. Some clubs do have them.

A mate is waiting for his 500 barrel for his Blaser- 500 Jeffery I think. I am now looking forward to being there when he fires it.