How much powder to fireform for 30-8mag?

[mram10]

I am ff some 300 wby and other stuff to my 30-8mag. I will use some cheap bullets (155 sierra) and some leftover powder. How much powder should I use?

Also, can I use a light load of mixed powders? I have little bits of 4350,4831, 380 and 760 that I would like to use for something.

Thanks.

 

[wapiti25]

Are the 300 wby brass long enough to make 30-8mm mag? If you can not find 7mm STW/8mm mag brass I would use 375 H&H and resize. For powder I would go to 300 wby starting load.

 

[mram10]

Are the 300 wby brass long enough to make 30-8mm mag? If you can not find 7mm STW/8mm mag brass I would use 375 H&H and resize. For powder I would go to 300 wby starting load.

They are long enough, so why use 375? 7stw is hard to find and not cheap. 300wby is easier to find and easier to convert than 375 h&h.