The early Weatherby rifles had a long free-bore. 0.50" seems to come to mind, but could have been as much as 0.75".
The newer ones have standardized on 0.375" or 3/8".
It's not the accuracy handicap some imagine. Neither is it a "fix" for an overbore cartridge. It's a way to deal with possible pressure excursions due to high temperatures where some hunting with Weatherby cartridges occurs (S.W. USA, Africa, ect.). It also makes a top-end cartridge a 'little bit better', at least it did to Roy Weatherby when he was starting the company 60yrs ago. It made excellent sense back in the '40's and '50's. Not really neccessary now, but, thats part of what makes a Weatherby a Weatherby.....
I have a Vanguard (not MOA model) and it has the 3/8" freebore. It too, is sub-moa accurate.
Remember, they are HUNTING RIFLES, not target rifles.... anything better than 1.5moa is nice, but not neccessary...
And, with RL25 and a Hornady 100gr SPT it gets 3,600fps+ and sub-moa even from a 24"bbl, so I don't really miss the extra 2" of barrel length...
I just wish it'd had a better trigger. It took a $100 Timney trigger to "fix" it....
