I don't know for 338 Norma. Using 300 Norma brass in my 30-338 Norma Imp I bought a .335 and .336 bushing. I would bet you could add .030 to that (.338"-.308"= .030') and be good. So .365 and .366". My loaded rounds are .338-.3385 and my chamber is .341" so with the brass spring back I don't even need to size the necks. The neck OD after firing runs .335 to .336.