Re: What round to use 375RUM or 378Weatherby
Probably not quite with the RUM cases but you will get close enough that you will never know the difference.
I have developed loads for several 26" barreled 375 RUMs that topped out at around 2900 fps with the 300 gr pill. These were what I would call max load levels in these rifles. If you get a custom chamber you may ba able to handle a bit more pressure but not a whole lot.
You will not see alot of velocity gain from 26" to 28" in the 375 caliber. Actually, I would guess less then 30 fps. I would personally opt for a shorter, stiffer barrel but it all depends on what type of rifle you are going to build.
In the field and at long range, you will be hard pressed to tell the difference between a 375 RUM and 378 Wby, except on the recoil end of things. Course if you have a brake on the rifle neither are hard to shoot.
The 375 bore makes the 338 bore look silly effiency wise. Do not think you need alot of barrel to get good FPS. You simply do not need alot of inches even with a 100 gr capacity in this bore diameter.
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