CMMG - AR15/M16 Ejection Port Cover Kit w/ Gas Deflector

I bought this knowing it was designed for use with a standard AR upper, but I had an idea that I could adapt it to my dedicated 9mm upper that has a much smaller ejection port. I took just the nylon deflector and glued it to the side of my FM upper just behind the ejection port. Works great, I am left handed and use a suppressor and this has completely eliminated any gas or particulates from hitting my cheek.

There really isn't much to this. The dust cover is shortened (obviously) to allow room for the little defector nub that sticks out. The dust cover pin just slides through the deflecter nun. I like to install the dust port cover before I install the barrel. The issue that I encountered is you can't use the typical clam shell type upper receiver block that most guys own. The clam type vise block Doesn't accommodate for the deflecter protrusion. I suspect that guys try to install this part from the wrong direction because they don't have the correct vise block. I used the DPMS Claw type upper receiver block. That allows the barrel to be installed without encasing the upper. As far as grinding on parts or shortening parts; I have no idea what these guys are talking about. Just remove the barrel, and install the dust cover before installing the barrel. That's the correct sequence. Good luck.

I like this design better than the old Colt design. It looks more modern on newer AR rifles and is lower profile. The problem is depending on your upper receiver you may have to custom fit the deflector to line up with the ejection port and the ejection port cover rod for it to work properly. A Dremel tool will come in handy for this purpose. I have CMT's and Guntec receivers that the rod would not line up until I took some material off the deflector, but after that, they fit tight against the receiver without any blow by. Just make sure you don't make them too tight, as the door can scratch the deflector when opening and closing.

Ordered this after shooting my AR9 with a supressor the first time. As a left handed shooter, I was getting peppered with unburned powder. This product massively cut down on the amount of blow back gas and debris. Good product at a fair price. Only con is I had to do some fitting on the deflector. The hole the pivot pin passes through was not parallel to the axis of the hole on my upper receiver. Some sandpaper and patience took care of that issue.

I used this kit for a 9mm build, it fit good and is great for the build, I would buy again.