Seems to me that controllability in a high-speed threat situation would be a problem, with this rig. Small movements of the left hand make large misdirection of the muzzle. A shoulder-mounted rifle can be cycled almost as quickly, and initially brought to point of aim far more quickly.
A conventional rifle should be faster as to the first aimed shot--which is usually the most important shot of all.
However, comparative testing on targets beats the heck out armchair opinions. For instance, trying this rig against a conventional rifle for the time to the first hit at a 10-yard target would be a start. I suggest as a target, a 55-gallon drum being rolled toward the shooter, with the "kill zone" being a 4" strip painted around it.
Wrap a rope around the barrel, with the Puller standing behind the Shooter. Shooter starts with eyes closed, and goes into action upon a signal of whatever sort. The stopwatch starts with the signal.
The real-world problem is that of readiness for an unexpected attack. Few are ready, regardless of the style of weapon. Or, they're so ready that there is little point to being there in the first place.
, Art
