Let’s just get something out of the way right up front. Placing the magazine on the ground in order to stabilize your AR-15 will not cause malfunctions. This technique has proven over and over again to be not only reliable but extremely useful. While I am dispelling myths… the 5.56 doesn’t tumble end over end through the air and Mattel never made M16s for the military.
The reason I bring this up is that the makers of the excellent line of Multitasker Tools recently made a splash with the introduction of the MagPod. The MagPod is a replacement baseplate for the ubiquitous Magpul PMAG. It is shaped in such a way that it provides a stable base when you are using the magazine as a monopod to stabilize your rifle and works as an aid in removing the magazine from pouches.
I think the MagPod has tremendous merit. I have personally used the magazine monopod technique with great success for a while now so I have no fears about this product causing malfunctions. Many people use products that attach to the base of their magazines that aid in removing magazines from their mag pouches. I view the MagPod as something similar but with the additional and useful functionality of stabilizing the rifle when used as a monopod. As with any product, time and testing will tell the whole story.