I had to to service some M4's for a local Hostage Rescue Team yesterday. I can tell you that I am truly concerned about the gas blocks, and they are in the process of being replaced with blocks made of stainless steel.

Between the bored hole for the barrel and the gas tube, running from the port hole towards the butt of the rifle, the aluminum has eroded away in less than one year, and is about 65% gone. In less than one more year, the material will be completely gone, and the systems if not fixed will lose pressure and be leaking gas back toward the shooters face.

All of these "TRICK" accessory gas blocks made of aluminum sure look like they have utility. However, after what I saw yesterday, anyone looking for an aftermarket block should not even consider aluminum for a duty weapon, or even for prarie dog shooting. Any weapon that will be used for anything other than ultra slow fire, should have steel.

Aluminum does not work over the long haul!!!!!!!!!