I know this thread is a little over 4 years past. I found it while looking for others load data for the several different variants of the .338-.300 Win Mag. I just ordered a .338-.300 Win Mag reamer from JGS. Went with a 35 degree shoulder, minimum neck “No turn”, had the reamer set up for the 230gr Hornady ELD-X’s to be .010 off the lands at a COAL of 3.550 in Winchester brass, so they will feed from a Magpul AICS Mag.
I thought what the heck. I own a .338 Ultra and a Benchmark built .338 Edge which is spooky accurate. I also am very fond of the .300 Win Mag chambering. I built a 28” 7mm-.300 Win Mag this last fall and it surpassed my expectations in performance and accuracy. I took a Mulie with it this last fall at 847 yards.
So I already have plenty of .338 bullets in stock along with .300 Win Mag Brass.