I think the idea here is that the equal and opposite force is the door giving way. I can certainly imagine using such a device on a solid concrete wall would give a similar effect as not holding onto a baseball bat hard enough. Boing! Try to think of a jack hammer, it's rebound is tremendous. But the asphalt does not give way like a door. So if I'm wrong (or is used on a bunker wall) I guess it could come back to bite you. Proper training should solve this.
Besides it is intended as a light weight force multiplier not a bulldozer. And in following the K.I.S.S. approach to design (Keep It Simple, Stupid) I can see Gas assisted Rams needing fittings, high pressure tanks, filling stations and that only increases weight and complexity. I'm talking about a self contained maintenance free, lightweight Ram. One that could be charged by a variety of sources from 12 volt car outlets to standard house hold wall plugs. And being that it would use a modified capacitor bank, it really doesn't care how or what kind of current it receives (AC, DC, 12 volt, 110, 220) it should all go through a resistor or solid state circuit of some sort anyway, and it gets charged, from a plethora of viable sources.
Andrew