I have a 375 JRS and use 8mm Remington mag brass right now. I would like to know if I could use 375 Wby brass and make it in to 375 JRS. I think the 375 Wby brass is better then the Remington brass

I have a 8 mag and a 300 weatherby and the brass is almost idenical other then the shape of the sholder

Just get some and run them thru the FL die and measure them and run the empty thru your chamber.

Check that the necks are not too thick as the 8mm sized up may have thinner necks than the .375 Weatherby.

What's wrong with the Remington brass?

I use .375 H&H brass to make the .375 Improved. That seems to work fine plus the headstamps are classic! You could even shoot .375 H&H's in your JRS?

The Remington brass is to soft. I use Lapua brass for most of my reloading and they do not make anything I can use to make the 375 JRS out of. Thank You I will try that