Bart Bobbitt's comments:
"The accuracy of the crown means the land and groove part of the
barrel must let the bullet's base exit evenly all the way around. When
this happens, gas escapes uniformly and evenly around the bullet's base.
If gas escapes unevenly (poor crown, even unsquare bullet bases), the
point of greatest gas release will push the bullet in the opposite
direction and tilt it. Tilted bullets leaving the barrel just don't
shoot straight; how far they move sideways depends on their velocity,
spin rate, and degree of tilt (or yaw, as it's sometimes called)."
High capacity is not an acceptable substitute for good marksmanship.