Todd C
perhaps the reason for an increase
Wednesday, March 21, 2018, 16:59

in perceived recoil is with the tapered case the unburnt/partially burnt powder is being pushed/puked out the case as an increased ejecta ( projectile ) as it still has mass and hasn't transformed into gasses yet. Whereas a sharp shouldered case attenuates a portion of the powder column, thus eliminating part of the "ejecta" and holding the powder in the case longer until it transitions into propellant gases.
Take .070 off the diameter of any cylinder and you have a great reduction in the capacity, thereby the "ejecta plug" is far smaller and less mass to add to recoil.