I just put a 6.5-300 Weatherby together on a pre 64 Win 70 H&H length action. The barrel was a Douglas 26 incher. The headspace is perfect. The gun will not chamber factory Weatherby 6.5-300 Weatherby's with 140 grain Hornady Interlocks. If I seat the bullets .020" deeper into the case they chamber just fine.

So it appears that my barrel does not have the SAAMI Weatherby Freebore. I am going to either get a throater and ream to SAAMI specs or shoot only reloads.

I have read that a barrel such as mine should be marked as to the non SAAMI Chamber due to pressure concerns. I know Weatherby Chambers have considerable Freebore.

I am assuming that it would not be safe to seat these factory loaded rounds .020" deeper to allow them to chamber as I am pretty sure the Weatherby Freebore is quite longer than .020".

I don't know if it is practical / possible to seat them deep enough to match the freebore. I am thinking I will have to pull these bullets and remove some powder if I don't add some Freebore to the chambers.

What are thoughts and experiences? Is there anything to be gained with the non SAAMI 6.5-300 Weatherby Chamber or should I just add the Freebore and bring it up to SAMMI Specs? The bore is excellent and the throat absolutely perfect right now.

After a bit of my own research, it appears the SAAMI Chamber is the way to go. So what are people's thoughts? Rent a SAAMI reamer or just get a throater?
It appears most people measure around .2037" Freebore but the Weatherby spec appears to be .2645" Freebore.

net net, renting the reamer is the way to go -- both have perils, ,but the whole reamer has less and less complications/measurements/failure modes