plawolf
Lieutenant General
as it turns out their is even more to the story. Firearms blog did a fallow up on their spotting of it. Unnamed sources state that groups like Hezbollah favor Israeli made weapons and accessories. They get them imported in from other parts of the world with the made in Israel mark scratched out. Now the magazine in that device is a Stanag style meaning its designed to fit any NATO standard assault rifle that standard is based on the ar15 so that mag release is a mag release basicly the grip is a magazine well with out a receiver.the advantage is you have a spare magazine ready to load right at you loading hand. As well as the extra control in shooting offered by the grip.
I think you may be overestimating the thinking behind that mod. The M4/14/AR15 have a side mag release catch. You cannot do an AK47 style mag bump to drop the spent magazine. As such, trying to release the spent mag with a fresh one already in your hand is not so straight forward and may cause you problems.
As I see it, the primary reason for that mod was to jury rig a tactical grip for added stability and control rather than to have a spare mag for quick changes. The M4 mag well was chosen because it was readily available. It may well be an option as an additiona magazine storage solution, but considering the extra weight of a loaded mag compared to an empty one, the marginal time and movement savings from releasing the mag and changing out the spent one compared to the standard mag change form a pouch, I would not be surprised if the shooter decided it was just not worth it to add a lot of excess dead weight to the front of his gun and just used an empty mag for the foregrip.
Personally, I would have just used a solid cylinder of hard rubber and screwed that to the bottom of that M4/16 to make a better tactical grip. Although if I had an AK47, I may give serious thought to using that idea for a tactical grip that doubled up as a spare magazine for emergencies since you would get real meaningful time savings with an AK47 style mag release system by using the mag bump method.