To TannerGun:
If you want to know, there is a very simple way of determining how much free bore you have. In my opinion, you need to know this when you are developing a load for a cartridge you are not sure what it is.
Take a fired case, just barely size the mouth, enough to start a bullet by hand, and it stays in the case.
Seat the bullet in the case, point first, enough to hold it in. Chamber the dummy round, with the bullet seated backwards, closing the bolt all the way.
Carefully extract the dummy round, and the amount the base of the bullet sticks out of the case mouth is your freebore. Use a flat base bullet. The base of the bullet stops against the origin or the rifling, and the case pushes up on the bullet.
As far as I know, freebore, or as it is also known, throating, is an inexact science. If the bullet protrudes about 1/4 to 5/16 of an inch, I would not consider it freebored, but as having a normal throat. 1/2 inch or longer, I would consider it freebored. Over 5/16 but less than 1/2 inch, well mayby, but watch carefully when you are approaching max. loads.
I know from experience that a short throat, or no throat at all can raise pressures hugely, even with mild loads.
If you can get ahold of a fired .300 Wby. visually compare it to your fired case, then compare the volume. If both are the same, then it is probably a .300 Wby. Many M70s in .300 H&H were rechambered to .300 Wby., some by Weatherby himself.
Another word of caution--if it is a .300 Wby., but NO freebore, then do not use the max. loads suggested in manuals for this cartridge, nor would I use Wby. factory loads.
