What's the optimum rifling twist if you want to exclusively shoot 100-120 bullets ? What powders,loads ?
You will probably need a different magazine box and follower. .378 Wby is a good bit fatter than the .300 H&H-based cartridges that the .300 Wby down to .257 Wby are based off of.Sure is easier buying a rifle rather than selling it. I have a 338-378 and can't seem to sell it. So a smith in CO who is in good with Weatherby will replace the bolt and re-bbl my rifle to the 257 WBY Mag. I think I'll have a 26" 5R Bartlien 10"twist installed.
Magazine, follower, bolt stop in the wrong place... The 257 and 338-378 are very different setups, and not much is directly interchangeable.Gunsmith did tell me that magazine work will be required .