I believe that 250's are not the optimum bullet for making long shots with the .338 Win., would suggest 225's or lighter when you can get them. Since you have the 250's there is no reason not to determine a good accurate load and shoot them for practice and learning.
There are a couple of considerations when starting to work up a load. Powder and primer selections are first, no sweat on the bullets since you have them. Check the manuals and internet sources (www.accuratreloading.com
is the first one I would go to) to determine a range that you can work within with the 4350. Then you really need to determine the overall length that you will be setting your die for. You can do this with guages (Stoney Point for instance) or trial and error in your rifle. Frequently the optimum OL will be longer than your magazine well, so if you are making hunting ammo you are restricted to the length that will fit into the magazine.
You may or may not want to compare Win primers with Win Magnum primers for this magnum case.
Load three or five rounds of each weight, starting at least 3-4 grains below the maximum listed. Shoot the test rounds slowly and use a pad so that your shoulder does not get beat-up. Your rifle will indicate which load it prefers, you might even have to go one or two grains over maximum if it appears that accuracy is improving and more velocity is needed.
Remember to record all the group sizes, how easily the brass extracted, O.L. and the details of the makeup of the best load.
Your rifle will tell you when pressures are approaching the danger point, as will the base of the cartridge case. Stop if you can feel that you need a slightly increased effort to lift the bolt. Also check the bottom of the cartridge case and see if there are flattened circles where your ejector plunger was located, or if the primer is really flattened in the pocket. Some loads show excell pressure by creating craters around the firing pin indentation, sometimes that is not a reliable indicator.
Good luck in your load development - it ain't rocket science but you should develope a routine that ensures safety and accuracy.