Re: not sure might b stupid ?
Along the lines of what Brent said.
338 Win Mag?
Break in with the cheapes ammo you can. If you plan to reload, then go ahead and use the factory ammo and get an idea of how it shoots.
Reload if you possibly can. Best load I have seen for the Ruger 338 I load for is 250 Barnes X over H4350. Work up loads from the Barnes manual.
If having others load for you, see if they have a way to measure headspace (like stoney Point). Get a stoney point dummy cartridge along with the dies so they can begin to tailor the OAL length for your chamber.