How is a 140 Interlock moving that slow going to perform on game?
While I haven't used that particular bullet, IME standard big game bullets perform really poorly at subsonic speeds. Plus they are going to ricochet like crazy.
Something like a Lehigh Defense Controlled Fracturing bullet is a better choice, but I don't think they make a 6.5.
Good reason to stay with 30 caliber for subsonic use - 30 caliber has options designed for subsonic speeds.
Another choice is a wide meplat cast bullet, or handgun bullet designed to expand at subsonic speed. Which is one reason to go with 35 caliber for subsonic rifle use - lots of readily available handgun bullets or molds to make them.
