Building an AR-15 from an 80% Lower Receiver with our 80% Lower Jig

Our AR-15 80% Lower Jig Assembly gives you the definitive guide when it comes to taking on an 80% lower yourself. Constructed of 6061 aerospace grade aluminum and prepared in our state of the art HAAS CNC machines and held to the strictest of tolerances, we have manufactured our 80% lower jig assembly to be used by anyone wanting to finish their own 80% lower. Featuring clearly marked dimensions and this online step by step guide, we are here for you every step of the way by offering our no cost live phone support should you need it. This 80% lower jig works for almost any milspec 80% lower receiver.

  • Patent Pending Design
  • 6061 Aerospace Grade Aluminum
  • Online Step by Step Guide
  • No Cost Live Phone Support
  • No FFL Required
  • Protected by The 1968 Gun Control Act
  • Made in USA
  • MSRP $ 130.00

Our AR-15 80% Lower Jig Assembly is designed to fit any milspec lower as well as numerous variants from other manufactures. Since we cannot buy every single lower out there, we do not maintain a list or guarantee they will work with all of the others out there. Because of our patent pending design used to locate off the rear take down pin we are able to locate on nearly any lower receiver. This jig will not fit lowers with fixed trigger guards without modification. Our 80% lower receiver jig assembly can be used on multiple lowers if used properly, but may require slight modification when selecting a variant manufacturer’s product.

How to complete an 80% Lower using the Vision Defense 80% Lower Jig.

Welcome to AR-15 80% lower finishing 101… What follows is an “instruction guide” for demonstrating how to use our AR-15  80% lower receiver and 80% lower jig. This does not mean there are not better or safer ways to finish one. If you think of a better solution and have some free time. Write it up and send it to us so we can post it here for others to read as well.

So Let’s Begin –

The first step is to obviously gather all the required tools necessary so we are not stopping in the middle of our project. The recommended tools for this project are listed below.

  • (1) 5/32 Jobber Drill Bit
  • (1) 3/8″ Jobber Drill Bit
  • (1) 5/16″ Jobber Drill Bit
  • (1) 3/8″ x 1-1/4″ Center Cutting Endmill
  • Drill Press or other capable equipment
  • X/Y Cross Slide Vise
  • Optional (1) Dremel with 1/4″ Grinding Head

Okay, once you have all of the above around, we can begin. To get started we will need to assemble the 80% Lower Jig around your first 80% Lower Receiver. Attached the Side Plate (A) and Side Plate (B) and use the boss on each to locate the jig in the rear takedown pin hole towards the rear of the lower. Then install Top Plate (C) over the top edges of both of the side plates.  Assemble the 80% lower jig “loosely” until you are able to insert all of the (4) top plate assembly bolts and the side plate cross bolt and spacer.

  • Top Plate (C) is clearly marked “1-1/4 deep”, The 80% Lower Jig provides you the outline or profile you will need to follow to make your cuts at that depth. The dimension is 1-1/4″ deep from the time you touch the material, so set your stop on your press accordingly when you are setting up your jig.
  • We suggest setting up with the 3/8″ Jobber Drill and drilling 1-1/4″ deep in every corner radius of Top Plate (C). This will make it easier when you switch to the 3/8″ x 1-1/4 Center Curring End Mill later on. Below is a simple picture diagram of our suggested drilling locations for this step.

visiondefense_80% lower Jig Instructions_1

Step 1-B

  • Now after Step 1-A you should have a of minimum (5) holes protruding into your 80% Lower in the locations pictured above. The next task is to remove as much material inside of the remaining profile as possible with the 3/8″ drill. *Make sure you are not overlapping the holes with the drill, overlapping the holes will wear the drill and possibly break it. 

visiondefense_80% lower Jig Instructions_2


Step 2

  • Now we are switching to the 3/8″ x 1-1/4″ center cutting endmill. After the completion of steps 1-A and 1-B you should have created a “web” system in the center of the lower. Now you are going to use the center cutting endmill to plunge into the center of those “webs” to remove the remaining material.  *The depth of the endmill cutting should not exceed 1-1/4″ deep as this is the finished depth of the pocket while utilizing “Top Plate C”

visiondefense_80% lower Jig Instructions_3

Step 3

  • Now that you have removed all of the material in the lower fire control group of your 80% lower receiver. It is now time to switch the top plates. Begin by removing (Top Plate C) and replacing it with (Top Plate D)
    • You will notice that just like Top Plate C, the replacement top plate also has profiles with the depth of cut marked out for you.
  • Just as before you are going to drill as many holes as possible in the rear profile (near the buffer tower) of Top Plate D.  We have recommended the (3) locations in which we chose to drill our holes.

visiondefense_80% lower Jig Instructions_4



  • Now, You guessed it! We are going to bust out that 3/8″ center cutting endmill again and remove the “webs” and remaining material in the rear portion of Top Plate D.


Step 4

  • Since we have Top Plate D installed, we can go a head and take care of the front portion of that plate now. This portion will drill the location holes for the trigger slot in the bottom of the fire control group pocket.


  • What you’re going to do is, while using the 5/16″ Jobber Drill you are going to drill (1) hole at each end of the slot in Top Plate D, and then a final hole right in the center of the slot. This will allow you to clean up any remaining “web” created by the drills with the 1/4″ dremel we mentioned at the beginning of this post. *You can also use a 5/16″ center cutting endmill if you have one available.

visiondefense_80% lower Jig Instructions_6

Step 5

  • Now lets move to the side plates and get this thing wrapped up. This process is pretty straight forward. We DO NOT recommend drilling all the way through from one side. The chances of the drill “walk” is very high and could render the 80% lower receiver and all of your hard work useless.
  • With the lower and jig on  it’s side you will see your (2) trigger pin holes are ready to be drilled. These holes use a 5/32″ Jobber Drill to fit your hammer and trigger pins correctly. Drill through halfway into the cavity you created at the beginning of this post.
  • The other hole marked for a 3/8″ Jobber Drill is for your safety selector. Drill halfway through from each side, then all the way through from one side to align the holes correctly.

Step 6

  • That is it! You’re done! Now all you may need to do is “clean up” the finish on the inside and straighten out your cuts. This is where the X/Y vise and the center cutting endmills come in handy. But you can use a dremel or other type of equipment to clean it up.visiondefense_80% lower Jig Instructions_7