What needs to be done to my bolt going from .243 to 6.5 Grendel?

[adamjp]

If you take a common hunting bullet for the 243, say a 95gn Nosler Ballistic Tip, the 243 can reliably throw it at 3000fps. 1908fpe at the muzzle and 1094fpe at 300m.

If you take a 100gn Nosler Ballistic Tip for the 6.5 Grendel, a bolt rifle will also reliably throw it at 3000fps. 2000fpe at the muzzle and 1097fpe at 300m.

Now, take a 120gn Nosler Ballistic Tip for the Grendel, put it in a bolt gun, throw it at 2600fps. 1809fpe at the muzzle and 1113fpe at 300m.

'nuff said.