Powders for the .30-378 Wby?

[Love a Weatherby]

I been useing n217 with my some off my rounds doing fair. But not like I would like would really like to find the col off the 200gr partiton in 338378

 

[yobuck]

I been useing n217 with my some off my rounds doing fair. But not like I would like would really like to find the col off the 200gr partiton in 338378

I dont know anybody using that bullet in a 338x378.
Most are using a 250 gr and some the 300 gr.
The 300s shoot better in my sons with a 9 twist barrel so thats what he uses with Retumbo or the old H570.