I tend to agree---
with mparris71.
Buy as large a lot of new brass as you can afford and resign yourself to full length sizing it ALL, and trimming it ALL to uniform length. That way you won't have to figure out which is which batch, and you'll have removed at least one set of variables in your quest for uniformity, and thus accuracy.
Hint: It is a hassle, but try to rotate the brass so that you have loaded it all about equal numbers of times.
Another hint--Surf the net a bit. I think you can beat that price somewhat. You might want to order more than 50 at a time.
What kind of powder are you going to use? How about bullets? I had every good luck with Alliant ReLoder 19, and the Hornady 225 gr. Spire Point bullets. Happily, these also happened to be the least expensive bullets I could find, while at the same time being quite accurate.
YMMV, of course. What kind of rifle did you get?
Hope you enjoy your association with the .338 WinMag as much as I have mine.
Best,
Johnny