When it comes to finishing your 80% lower receiver, there are a few options to consider. To finish the 80 lower, most builders use a jig to aid in the machining process. The 80 lower jig ensures that you drill or cut into the lower where you should, and you don't where you shouldn't!
AR-15 builders have a number of 80 lower jigs to choose from but they are generally broken down into two main categories. The jig that's most commonly known and offered by most 80 lower manufacturers is the drill press jig. The second less commonly known, but far superior is the router-based jig.
80 Lower Jig Comparison Chart
Drill Press Jig
The drill press jig requires the builder to use either a handheld drill gun, or a drill press to finish the lower. The jig guides builders in drilling upwards of 42 different holes, in essence creating the "swiss cheese" effect. Some drill press lowers start the drilling process using a smaller drill bit such as a 1/8" bit and then graduate up to a larger bit such as a 3/8". This process of creating 42 different drill holes eventually carves out the fire control pocket, allowing you to then add your lower parts kit. Like all 80 lower jigs, the drill press jig allows for 3 horizontal holes to be drilled in the side of the jig to accommodate the fire/safety selector switch, the trigger pin and hammer pin.
At 80-lower.com we offer two options for the Drill Press jig. The Rugged 80% Lower Jig and the Tough 80% Lower Jig. Both will certainly get the job done but they do vary in quality, durability, and pricing. The Classic model comes in at $114.95 and is good for an estimated 2 completed lowers. The Advanced model comes in just $10 more at $124.95 but it will get you two more builds, for a total of 4 with this jig.
The router jig differs from the drill press jig in that it requires two types of machining. The Easy Jig (80% Lower Jig) starts similar to drill press in that you still need to create the "swiss cheese" but it requires far less drilling. The router based method only requires you to make 10 drilling holes, less than 25% of the holes needed with the drill press jig. The next step is where the big time savings is. Once the "swiss cheese" has been created, it's time for the fancy end-mill bit and router. Using a handheld router, the builder makes pass, after pass jumping to and from each of the previously drilled holes. Using the router, the builder makes 6-11 different passes to finish the trigger pocket.
Note: The router jig system does require a special end-mill bit which can not be purchased at your local hardware store.
The 5D Tactical 80 Lower Jig is a more expensive option. However, the strength, durability and speed make it one of the most popular options. Using the router based jig system, a builder can machine lowers in 1/2 of the time and complete upwards of 20 different lowers!
Regardless of your preference, we at 80-lower.com have equipped you with the means to finish your lower receiver and AR-15 Build Kit! Happy building!