Have in my possession 257 Bee, 6.5-300 Bee, 270 Bee, 300 Bee, 340 Bee & 375 Bee. The last 3 are on the same Win Model 70, the first 2 are on another Win Model 70 and I have another 257Bee on a Weatherby.
This is my take on this scenario. Back in 2000/01 I started developing my own wildcats based on the 416 Rigby Improved case. Had looked at the 300/340-378 case, but 2 things stood out to me that would hamper what I wanted to do, first was the belt, took up too much room in my chosen platform action, second was the radius shoulder and neck length. I wanted as much case capacity as I could get. The cost of Weatherby brass was another factor here, it is like gold prices…
I stumbled upon a huge supply of Kynoch 416 Rigby ammo that had been stored and forgotten about in the 60's or so.
So, I had plenty of brass to play with, just had to pull bullets and that gave me brass. I didn't know that cordite was very difficult to remove, however I managed.
So, this is what I started with, developed my design on 30, 33, 37 & thought about 7mm & 416.
Now, the difference in performance with a case the size of the 378 Bee, or 416 Rigby is not huge, but when you can safely exceed 3400fps with the desired bullet weight, read that as heavy target bullet, the increase is downright a game changer at distance.
Using 120g+ of powder is now getting very expensive, but if you're only hunting, it really doesn't matter. I built mine for hunting and ELR steel shooting, already burnt out 2 barrels, one 30 cal and my current 33 is about done and very tired at 900 rounds.
Just don't shoot fast…
I agree with
@FEENIX .
Cheers.