I am still looking for loading data for the 338 win mag necked down to 8mm.I have dies cases and bullets just need to know what powder and how much.I have some 200 gr 8mm Nosler Partitions.

I think you would be safe with any load for a .338 Mag with similar weight bullets. You are only talking the difference of .32(8mm) to .338. Just use a .338 load with the same bullet weight and back off to the starting load. IMR or any of the other 4350 powders should work well.

bowhuntr

You could also use 30/338 data or 308 Norma data. A 308 bullet is going to be longer than an 8mm bullet of the same weight, so in theory you should have less pressure with the 8mm. As long as you used starting loads and worked up from there you'd be fine. Either that or look at 30/338 data and 338 Win Mag data, and start in the middle! It shouldn't be too hard to put something together. Good luck!

One of the earlier Speer manuals had loading data for the 8mm poor mans magnum which is the 8mm/338. # 8 or 9 I think.