Carbon ring. Try cleaning your throat and chamber with JBs bore paste if that doesn't help you might have out of spec ammo color a case with a sharpie and open and close the bolt a few times that should tell you where the tight spot is but I'd JBs the shat out of that chamber too.
This...
Also, I'm guessing by bullet weights it's maybe a 6.5 CM??
The 140 is going to be longer to the ogive than the 125.
If there is a carbon ring it could be contacting the bullet