In reality those gas groves do very little in the event of a blown primer or case seperation. The idea is good but in practice the groves too small and shallow. If they were deep enough and located properly then they might help some but would in them selves cause problems with un suported sections of the case and primer. In the pictures it lookes like a ring around the primmer. If the firing pin punches through the primmer then the gas is vented into the hole surounding the firing pin and not to the vent ring around the primer. If the vent ring had a line cut to the center of the firing pin hole this would leave the primer unsuported in this area and would allow the primer to flow back into this cut causing the rifle to be hard opening at best and allowing the primmer to blow along this line at worst. The grove from the ring around the primmer to the out side of the breach is far too narrow and shallow to allow the volume of gas fron a blown case to escape quickly. These features may help some but not enough!!! The hole idea is not to blow primers or cases and with modern components it one sticks to the proper loadings this is not a problem. Think about it, with modern rifles firing either good, sane hand loads or factory ammo, when was the last time you saw a blown primmer? Also with the pressures double rifles are built to take using magnum primmers drastically reduces this problem.
Most of these problems date back to the cordite days and though worth keeping in mind are not much of a problem today.