Thank you, I will get in touch if I have trouble with working up loads. I think I'll try Ramshot X-Terminator first - have you had any experience with that one?
If I get the rifle approved for roe deer (currently just for target) I will most likely try 62gr GS Custom copper bullets driven fast (3400fps). I don't see any reason why they won't work very well. I think the Nosler 70gr BT would be a good option too.
From what I've read I agree that for hunting bullets above 85gr can't be driven fast enough.
I think my fascination with the cartridge is that it will be relatively cheap to shoot (won't cost much more than shooting a .223) and a little bit different. I like the fact that cases are easy to make from .223 brass just by full length sizing, no fireforming steps etc.