The premise for this article was sparked the week before a coyote hunt when no one had 5 round magazines in stock for my AR-15 (In AZ, you can not hunt with a semiautomatic rifle with a magazine that holds more than 5 rounds). I guess now I needed to convert and block some of my 20 round Colt magazines to be legal. I’ve never converted a 20 round magazine before, and for my disclaimer I say this: They are your magazines, they are your responsibility - so don’t blame me if you damage them! I’m sure there are MANY other methods out there on blocking magazines, this is only ONE method. It doesn’t damage the magazine (like simply drilling a screw through the side of it) and when you are done hunting you can simply take the block out of the magazine and have your 20 round mag back. Another thing, I’ve only done this on Colt magazines (seem to be pretty old models too), I’m sure this method can be adopted to fit just about any manufacturers though. Different measurements may be required is all. Let’s get started!

First, get yourself a piece of aluminum 1/16″ thick x 3/4″ width.

You will need to figure out how long to cut this to so the magazine will hold 5 rounds, and only 5 rounds. It may take a couple tries, just be sure to err on the side of a longer piece. You can always cut it or file it down to fit. I recommend sliding the full piece of aluminum down the back of the magazine to figure depth. For mine it was about 4″.

We will then bend the second piece that will fit directly under the floorplate (see image). You’ll need to cut this piece to length.

This is where we’re at:

Now,  you’ll notice as you slide this up into the magazine that the mag lips that hold the floorplate down get in the way of seating this piece of aluminum all the way into the mag. On the piece of aluminum, mark with a black marker where the obstructions will hit from the magazine. We will be filing this part off. (Note the black marker, this part will be filed off)

It may take a couple tries to get it an exact fit, and an exact fit is probably not even necessary, it just makes me feel better! Here is the final piece:

Now all we have to do is insert it into the magazine and install the floorplate.

At this stage all you need to do is verify 5 rounds, and ONLY 5 rounds fit into the magazine. If it is too long, just take our piece of aluminum out and file or cut down the end some more until a perfect fit is found. That’s it! You are ready to hunt with your AR-15!

Posted on March 20th, 2009 by jll-sgc
Filed under: FAQ, Gunsmithing News