Hm - when I was developing my 9,3x74R load with GSFN mono solids I did it with close support from Gerard from GS - he insisted on using magnum primers with drive band bullets - in his words:

"One of the big differences between drive band bullets and smooth bullets is the lightness with which a drive band bullet slips through the throat of the rifle and into the rifling. The resistance to engraving is about a quarter of that of a smooth bullet. If you use a magnum primer the pressure from the primer igniting will move the powder charge and the bullet forwards so that, when the powder ignites, the bullet is already engaged in the rifling and you have artificially created a bigger case. As we know, the same charge in a bigger case lowers pressure.This whole principle works best when the selection of powder is such that the bullet sits tight on top of the charge. The principle is almost unnoticable if a very fast powder is used with low charge levels and there is a lot of air space in the case. Air is compressed and the bullet does not move under primer ignition alone."

I don't know about pressure, but recoil was noticeable "softer" when using mag primers in my case.