Speed freeks love the 140s. Sierra 140s shoot very well jumping, but they are not high velocity bullets as they will detonate on shoulders.
I am very anal on accuracy first, this is why I stress matching the freebore to the intended bullet to be used. Most of these 7mm will shoot sub 3/8" groups, and often much less. Also, the bullet will LOVE a particular distance from the lands for best accuracy, and when you can not maintain that distance over time and wear, accuracy will degrade.
Also, a guy wanting to shoot 140s may want to consider matching the twist rate to the bullet. Years ago, I wanted to shoot the 140s at warp speed to maximize the point blank range and create tremendous internal damage on the deer. I build a 7 STW with a Pac Nor three groove 11 twist. I shot the 140g Nosler C/T bullet at 3700 fps into groups the size of a pencil eraser. The reamer used had zero freebore for this 7 STW. Big Kansas deer, near and far died in their tracks, with one exception of a 360 lb buck shot at 580 yards, he took three steps and fell over. That big buck had a tremendous rack, but he was so old, he did not have brow tines.
Bullets will only take so much rotational torque before the base of the bullet will deform during obturation, which creates flyers... another can of worms that leads you to slow "most accurate" loads.
The goal is to shoot 3/8" and smaller three-shot groups that repeat time after time. When you achieve these tiny groups, a 600 yard shot will be easy, in as far as the gun's capability.
