Howdy. I have a 6.5-300 Win Mag with the belt turned off from it. My rifle was throated for the 155gr SMK so I don't have any 140gr data for it. But as suggested above I used 264 Win Mag data to start with and never had an issue. When this rifle was built was before the internet was around so I was on my own. Same for my 6.5-300 WWH. But never even had a close call using basic safety procedures and precautions and 264 Win Mag loads to start with.
Good luck and be safe.