View Full Version : 80% Arms EZ Jig and Lower review (Long Read)

08-21-2014, 2:46 PM
I was in the market for an “80%” lower kit and stumbled upon 80% Arms looking for a solution that didn't require a drill press or CNC. The parts from what I had seen looked very nice and I was quite intrigued by the EZ Jig, as it uses a router method and much faster order of operations. I also like to support local companies, especially in California where the firearm industry needs support.

The lower I purchased along with the jig was their Anodized 7075-T6 AR-15 pattern receiver, which has a very nice design with an integrated trigger guard and nice curves, specifically around the mag well. The pistol grip screw hole came pre drilled and tapped, a manufacturing step some DIY lowers do not have completed, as well as all other machining steps before the part legally becomes a “firearm” in the eyes of the BATFE. Overall first impressions were good and build quality looked exceptional, more about the lower a little later.

I chose the 80% Arms EZ Jig specifically because I wanted to build a custom AR without using a drill press, as I do not have access to one. The Jig itself is very well thought out, fits together nicely and secures with bolts. The jig has 2 main side plates to hold the lower with guide holes for the selector switch, hammer, and trigger pin holes. There are different top plates for the various types of steps needed to finish the receiver. 80% Arms thankfully lists all the parts needed to complete the lower in their build guide with McMaster part numbers. Since I do a lot of custom A/V installs, as well as construction I have quite the toolbox (or boxes), so I already had a very nice drill and various other equipment like a vice.

The first step is drilling 10 holes into the lower with a 3/8 drill, this is to remove the bulk of the material in preparation for milling out the pocket. This process is fast compared to the dozens of small holes most other jigs use. One of the ingenious design decisions is the inclusion of depth gauges built right into the top jig plates, clearly marked “Main” & “Rear” for their respective pockets. Whatever top jig plate you are using, the other one has the correct depth gauge making it really easy to check that your drill bit collar hasn't slipped between holes. Once the main and rear pockets are roughed out, the next step is to mill out the main/trigger pocket using a router. This involves swapping top plates and bolting on a large support platform for the router to sit on.

Using the router on top of the support plate it’s pretty easy to make light passes milling away the material (stronger alloy means longer milling time and shorter lighter passes), lowering the end mill after every pass or so. Again, the integrated depth gauge proves very helpful for double checking cut depth and making sure you are not cutting too deep at a time. While the router method is not as precise as a drill press, it certainly is a lot faster. The process is the same for the rear shelf, using a different top plate to guide the router. The trigger hole is milled the same way, after drilling a starting hole through the lower.

Something very important to keep in mind is the RPM of your router. An RPM that’s too high will cause the end mill to snap at the collet because of too much lateral force. This is important if your router doesn’t have an adjustable RPM. I used the Dewalt router recommended by 80% Arms, and while it got the job done I was really not a fan of the router’s design and would not recommend it personally for regular use. The last steps to be completed are drilling the holes for the selector switch, as well as the hammer and trigger pins holes in the side of the lower.

The completed product looked rough but after some cleaning and some additional milling the main pocket of the lower looked fairy nice but still a tad rough, however I chalk that up to the router itself and since this was my first lower. If you had the patience and/or better equipment the main pocket could be smoothed out completely, but I found the work adequate by my standards. The PDF and online video guides proved very helpful with step by step instructions, easy to reference if you need to double-check a step.

Using a Stag Arms lower parts kit I started installing parts one at a time until I hit the snag. To make a long story short, my magazine catch slot was out of spec. After a quick email, 80% Arms had me send them the lower, and I got a call where I was informed my particular lower was part of an early production run that had slight issues. I must say their custom service is impeccable; they fixed my lower and sent it back in a very acceptable time frame, and after the modifications were made the mag catch fit fine, as well as all the other parts. I very much appreciate a company willing to stand behind its products and provide more than adequate custom support.

After much time waiting on parts I was able to make it down to the range and test fire the build for the first time. The lower performed fine with no signs of stress and fulfilled every expectation I had. In my opinion this is a very well designed lower in both form and function. The only real issues I experience are reserved for the EZ jig itself, particularly the way the fire control pocket is milled out, but this could easily be remedied by using a higher end router that is more precise and less of a hassle to work with. Total cost was around $300 after I returned the router to the hardware store, it simply wasn't worth keeping at around $100 with tax.

Overall this is a much faster solution than most traditional jigs and solutions, and it allows the completion of an “80%” lower receiver without the need for generally expensive machines such as a drill press or a CNC system. I would wholeheartedly recommend it to anyone interested in building an AR pattern firearm, especially those new to the practice. I think the slightly higher than average cost of the jig justifies itself, especially in the case you wish to mill multiple blank or “80%” lower receivers.

Here are some pics of the finished build. The full resolution versions of these and other build pics can be found here (http://imgur.com/a/fcP7A)


08-21-2014, 2:54 PM
you didnt take any pics of the pocket before you installed the fcg ?

08-21-2014, 3:14 PM

Look, it's on semi-safe lol

08-21-2014, 3:21 PM
you didnt take any pics of the pocket before you installed the fcg ?
Not on this particular lower and I didn't feel like pulling the FCG out for this review. I plan on doing another Lower from 80% Arms at some point, hopefully then I will have the foresight to take some pictures before it's assembled.

Look, it's on semi-safe lol
I think the pocket is slightly shallow and the selector switch won't turn a full 90 degrees. However after a trip down to the range the safety is fully functional, it's just a quarter turn instead of a half turn.

08-21-2014, 7:08 PM
:iagree: Superb !!!!!

08-21-2014, 7:59 PM
Nice write up and lower looks good..got mine on order and should be coming in a week or 2. Pretty excited since this will be my first as well.

08-21-2014, 9:57 PM
what's up with the wide screen format? got a head ache trying to read this.

08-21-2014, 10:41 PM
what's up with the wide screen format? got a head ache trying to read this.

Sorry about that. I formatted the review in Microsoft word as it is pretty long.