Mods for CMMG Guard to work with unmodified Colt mags

Modify the ears of the mag block so it doesn’t hit the bolt carrier.  I just used a disc sander and ground down the ears.FeedRampEars1

Picture below shows how high my ears are after grinding.FeedRampEars2
Modify mag catch for unmodified Colt mags.  I initially started at about .040″ which cleared but was having malfunctions when firing as I think the mags were moving and rubbing on the carrier.  You can see i’m close to .100″ now.  I think if I were to do it over, I would start testing around .060 – .080 now….but what I have now is working so I’ll leave it alone.


Removing more material from the mag catch required the feed ramps to be deepened on my Hahn mag block.  I happen to be using an MGI lower and a 556 mag well with Hahn block that has always been a little small for this magwell which I remedied years ago by bolting the mag block in place.

Lastly, since the mag catch was lowered, I lost bolt hold open functionality.  Little TIG welding underneath the ‘tab’ fixed that.


Youtube video of this configuration running in full auto: