Prolly so. Prolly just go with 7-300 Roy. Already have the brass for 300 Weatherby, and 6.5-300. But can't go straight to 6.5 from 300. Shoulders crush. Takes 7-300 dies then 6.5-300 dies. I have the dies and the brass. I just wanted something that would be far and away faster than the 7STW or 28. Looks like 7-300 will be just on par with those two
You are correct, the 7x300 WBY is essentially a clone to an 8mm mag case necked down to 7mm, AKA 7mmSTW.
Ive been using 7x300 wbys for about 50 years for l/r hunting in PA where at one time they were probably the most popular l/r cartridge there.
That cartridge actually derailed the 6.5x300 there in the early 70s after Hornady introduced the 162 gr hpbt 7mm match bullet.
As for the 7x378 wby, again that cartridge along with a 6.5 version on that case was experimented with also there many years back. But for various reasons it never went anywhere.
Howard Wolfe, who was a popular l/r gunsmith there and also an early pioneer of the 30x378 wildcat cartridge, had built a large 3 lug action to accommodate the 30x378. But others thought that the action might also allow for trying the 7 mm and 6.5 bullets with the 378 case, much to the dismay of Howard. He did agree to chamber a shortened version of the 378 case necked down to 7mm for at least 1 man that I'm aware of. The shortened version case is one that he had developed for use in shorter 30" barrels at the 1000 yd matches at Williamsport.
The powder capacity of that shortened case is a duplicate of the modern 300 Norma case.
I have been using that case with 190 gr SMKs with a MV of right around 3400 for quite a few years for l/r deer hunting With a gun built by Howard on a Mark V action.
I also have one of his actions being #29 of I'm not sure how many, which was a 30x378 for many years, but which now has a 338 barrel installed by Bruce Baer for his Big Baer case.
The future is always forward not backwards, and that means bigger bullets not smaller ones.
