A friend's 6.5x68, with 10" twist doesn't want to shoot anything longer than the 120gr. TSX (same length as normal 140gr. lead cored bullets). The 130's and 140 TSX are not stabilzed at over 3,000fps in this 'slow' twist, yaw and tumble.
The 120gr.TSX, although lighter for normal big game weight in this calibre, will lengthwise hole a moose, one end to the other from 300 meters. Moose refuse to take another step when you do this.