There is a gunsmith in Sherbrooke who can reload and develop loads for his customer if you don't already do it yourself.
Price is not cheap but you get ammo that will work best for your rifle. Contact me by pm.
I suggest you to start to make your own ammo. A box of 20 round for my 338 LM cost me around 20$ VS factory ammo that will cost between 150-180$ (and sometime more) per box.
Where do you shoot ? I'm from Sherbrooke and I never met someone else with a 338LM. What rifle do you own ?