I'm really enjoying this thread as I have been a Weatherby fan since I was a kid, and I have some random thoughts. My dad bought his first Weatherby (300 Wby) at 19 yo just like I did. He also had a 240 when I was coming up and he now has a 257.
I have a 257 accumark that is the most accurate factory rifle I've ever been around. In it's prime it would shoot five shots that a dime would cover all day long every day. You could clean it and it would put the first one exactly where it would put the 100th one.
All my life I've heard people and read articles that talked about Weatherby rounds being less accurate than their counterparts. It went against my observations. When I got into custom rifles I started building Wby calibers for the most part. I once had a 300 Wby built by a prominent builder, and they tried to get me to build it in their proprietary 300 magnum that is known for extreme accuracy. I already had brass and dies, but I asked one of the employees in reality how much more accurate was their 300 than the Wby. He immediately said it's not but do not tell the owner that I just admitted that to you.
A good friend started building rifles several years ago and he got a lot of advice from a well know hall of fame benchrest shooter who is a builder. This man told him that freebore was not detrimental at all to accuracy. He said if you build it right it will shoot.
I played with a bone stock 378 Mark V Deluxe a few years ago. It was a blast... I ended up developing a load with a 350 grain SMK that would shoot 1/2-3/4". You did have to let it cool before shooting that third shot though.
Roy Weatherby started developing his calibers 80 years ago! They are cool classics today that still match up with any of the "modern" cartridges, and they were way ahead of their time when introduced.