Seating the bullet touching the lands changes the pressure curve of the load. With a gap, The bullet overcomes inertia and frees itself from the neck at a specific point in the pressure curve. It starts to move, pressure increases as it moves, it engraves on the lands still in motion, pressure is still building and reaches its peak when the bullet is a few inches down the tube. where it reaches max. If the bullet is seated in to the lands, it has to overcome neck tension plus the resistance of the lands to overcome inertia. This will create a sharper and higher pressure rise and change the curve and also the resultant barrel vibration. A short jump to the lands will not allow the bullet to tip or loose whatever concentricity the bullet has from the neck. the bullet striking the lands will set up it's own vibration wave. but it is minor to other stresses. Bottom line, a small jump will cause less barrel modulation. IMHO. JB
