Originally Posted by bamashooter

This might help your need either locked in to a portable vise or attached to some other platform. I use mine in a portable vise on those few occassions as the need arises. Regardless, it's handy to have and if he ever runs out, which he did with the black ones, I doubt if any more will be available. If you get one, during insertion, make sure and press the magazine release at the same time or it won't go fully in.

Lower vise block M&P 15-22 White