Free Shipping On Orders Over $199!

80% Lower Jig Instructions

Drill Jig Instructions for 80% Lower Receivers…

What follows is the detailed process (one of many) to finish your AR15 or AR10 80% Lower Receiver into a ready to use part. TAKE YOUR TIME, be sure of each cut (check twice, cut once) and use the Drill Jig more as a “Point Guide” than a Jig and you will be able to use it several times if you like. It is only meant to be used as an actual Drilling Jig ONCE…

LEGAL – We’re pretty sure that everybody knows this already but we have to make the statement that if you choose to finish your 80% Lower into a functioning Rifle part, FIRST check with your state and local laws to make sure that it is legal to do so. Of course IT IS from a Federal Law standpoint as well as our 2A but the local govs can also be a road block to happiness…

Tools that you will need…

Besides the following list of Drills and Mills, you would be best served to use a free-standing Drill Press to complete your Lower. Hand held drills DO NOT work very well at all….

  • 3/8″ Drill Bit…
  • 5/16″ Drill Bit…
  • 5/32″ Drill Bit…
  • 1/8″ Drill Bit…
  • 3/32″ Drill Bit…
  • 3/8″ Std Length End Mill…
  • 5/16″ Std Length End Mill…

Each instruction spelled out below corresponds to the image just above it. You may review all of the images to get a brief overview, or, we highly recommend that you read through everything BEFORE BEGINNING your Drilling and Milling to have a basic understanding of the entire process before you start.

 

80 percent lower AR-15-Drill Jig Instructions

 

STEP 1 – First align either Side Plate to your 80% Lower and insert two Long 1/4″ Bolts through to fasten all three pieces together – DO NOT tighten yet…

 

80 percent lower AR-15-Drill Jig Instructions

 

STEP 2 – Then add any Top Plate (Slot Drill Plate shown) and use four short 1/4″ Bolts to secure the Plate leaving bolts loose once again. Place entire assembly on flat surface (Drill Press Table) standing upright and make sure everything is square and true. Tighten all fasteners starting with Side Plate bolts…

 

80 percent lower AR-15-Drill Jig Instructions

 

STEP 3 – Place Entire Assembly on side (Side Plate Bolts UP) and use 3/8″ Drill Bit to drill Selector Switch Hole. NOTE – You can go ahead and use the Drill Jig to Drill the Selector Hole through, or just start the hole in the side of the Lower and go back later to finish. We’d recommend to just drill it through here…

 

80 percent lower AR-15-Drill Jig Instructions

 

STEP 4 – Next, use the 5/32″ Drill Bit to drill both the Hammer Pin Hole and Trigger Hole. Once again, you can either drill through or just “start” those holes…

 

80 percent lower AR-15-Drill Jig Instructions

 

STEP 5 – In the event you did not attach the Drilling Top Plate in the first step, remove the existing Top Plate and attach the Drilling Top Plate with same four short 1/4″ Bolts. Square and Level everything again and then tighten all Bolts once again…

 

NOTE – You may wish to remove one long 1/4″ Bolt (towards rear of 80% Lower) at this point or in the next few steps. BEWARE when you are Drilling or Milling at towards the rear of the 80% Lower that you must REMOVE that long 1/4″ Bolt so you don’t destroy a Drill Bit or End Mill…

 

80 percent lower AR-15-Drill Jig Instructions

 

STEP 6 – With the Entire Assembly standing upright, start drilling with the 1/8″ Drill Bit at every hole shown above as “Green”. You can either “start” each hole to drill to depth after removing the Top Plate – OR, use the Drill Jig to drill each 1/8″ Hole to depth for the FCG main pocket at 1.250″…

 

80 percent lower AR-15-Drill Jig Instructions

 

STEP 7 – Continuing with the Entire Assembly standing upright, start drilling with the 3/32″ Drill Bit at every hole shown above as “Orange”. You can either “start” each hole to drill to depth after removing the Top Plate – OR, use the Drill Jig to drill each 3/32″ Hole to depth for the FCG main pocket at 1.250″…

 

80 percent lower AR-15-Drill Jig Instructions

 

STEP 8 – Progress Check so when you remove the Drilling Top Plate, your 80% Lower should look like the image above – reattach the Drilling Top Plate once again while Squaring and Leveling all pieces…

NOTE – Remove the rear most long 1/4″ Bolt at this time as you are going to be Drilling in the rear pocket area of your 80% Lower. Do this AFTER attaching and securing the Drilling Top Plate…

 

80 percent lower AR-15-Drill Jig Instructions

 

STEP 9 – With the Entire Assembly still standing upright, again start drilling with the 1/8″ Drill Bit at every hole shown above as “Green”. You can either “start” each hole to drill to depth after removing the Top Plate – OR, use the Drill Jig to drill each 1/8″ Hole to depth for the FCG rear pocket at 0.630″…

 

80 percent lower AR-15-Drill Jig Instructions

 

STEP 10 – Continuing with the Entire Assembly standing upright, start drilling with the 3/32″ Drill Bit at every hole shown above as “Orange”. You can either “start” each hole to drill to depth after removing the Top Plate – OR, use the Drill Jig to drill each 3/32″ Hole to depth for the FCG rear pocket at 0.630″…

 

80 percent lower AR-15-Drill Jig Instructions

 

STEP 11 – Progress Check so when you remove the Drilling Top Plate, your 80% Lower should look like the image above – Continue on the next Step with the Drilling Top Plate removed from the Assembly BUT do replace the rear most long 1/4″ Side Plate bolt for stability…

 

80 percent lower AR-15-Drill Jig Instructions

 

STEP 12 – Continuing with the Entire Assembly standing upright and the Drilling Top Plate Removed, start drilling with the 3/8″ Drill Bit at every 3/32″ hole shown above as “Red”. Use the Drill Press to drill each 3/8″ Hole to depth for the FCG main pocket at 1.250″…

NOTE – Remove the rear most long 1/4″ Side Plate bolt once again…

 

80 percent lower AR-15-Drill Jig Instructions

 

STEP 13 – Progress Check so when you are done drilling the correct number of 3/8″ holes, your 80% Lower should look like the image above…

 

80 percent lower AR-15-Drill Jig Instructions

 

STEP 14 – Continuing with the Entire Assembly standing upright and the Drilling Top Plate Removed, start drilling with the 5/16″ Drill Bit at every 3/32″ hole shown above as “Yellow”. Use the Drill Press to drill each 5/16″ Hole to depth for the FCG main pocket at 0.630″…

 

80 percent lower AR-15-Drill Jig Instructions

 

STEP 15 – Progress Check so when you are done drilling the correct number of 5/16″ holes for the rear pocket, your 80% Lower should look like the image above…

 

80 percent lower AR-15-Drill Jig Instructions

 

STEP 16 – Attach the Milling Top Plate (shown above) and continue with the Entire Assembly standing upright. Use the 5/16″ End Mill at a mid-range RPM and start with the smaller FCG rear pocket going to the least total depth of 0.630″. Set your down steps to about 1/16″ and when you press the End Mill down (plunging) into the 80% Lower material, GO SLOW. Then slowly trace around the outside perimeter of the smaller slot in the Milling Top Plate MAKING SURE that you have some “shank” of the End Mill ALWAYS running against the slot walls…

NOTE – If you screw up this part, it’s no big deal as there is nothing back there other than if you own a DIAS. The FCG rear pocket area makes a great “practice region” for getting used to Milling on a Drill Press….

 

80 percent lower AR-15-Drill Jig Instructions

 

STEP 17 – Replace the rear most long 1/4″ Side Plate bolt and FLIP end-for-end the Milling Top Plate (shown above) to continue with the Entire Assembly standing upright. Use the 3/8″ End Mill at a mid-range RPM and start milling the larger FCG main pocket going to a total depth of 1.250″. Set your down steps to about 1/16″ and when you press the End Mill down (plunging) into the 80% Lower material, GO SLOW. Then slowly trace around the outside perimeter of the larger slot in the Milling Top Plate MAKING SURE that you have some “shank” of the End Mill ALWAYS running against the slot walls – Remove the Milling Top Plate…

NOTE – If you screw up this part, your 80% Lower is “toast”…. BE CAREFUL, Take your time and Check everything TWICE (or more). You can do this because we’ve done it and made it all the way through just as outlined…

 

80 percent lower AR-15-Drill Jig Instructions

 

STEP 18 – Attach the Slotting Top Plate (shown above) squaring and leveling once again to continue with the Entire Assembly standing upright. Use the 1/8″ Drill Bit and drill the four holes shown in the above image as “Green”. There is only about 0.070″ of material to drill to you can just drill these holes all the way through to the Trigger Guard area…

 

80 percent lower AR-15-Drill Jig Instructions

 

STEP 19 – Continue by using the 3/32″ Drill Bit to drill the three holes shown in the above image as “Orange”. Again, there is only about 0.070″ of material to drill to you can just drill these holes all the way through to the Trigger Guard area…

 

80 percent lower AR-15-Drill Jig Instructions

 

STEP 20 – FLIP end-for-end the Slotting Top Plate (shown above) to continue with the Entire Assembly standing upright. Use the 5/16″ End Mill at a mid-range RPM and start milling the Trigger Slot at a depth of 1.250″. Set your down steps to about 1/16″ and when you press the End Mill down (plunging) into the 80% Lower material, GO SLOW. Then slowly trace around the outside perimeter of the larger slot in the Milling Top Plate MAKING SURE that you have some “shank” of the End Mill ALWAYS running against the slot walls – Remove the Slot Top Plate…

 

80 percent lower AR-15-Drill Jig Instructions

 

STEP 21 – Progress Check so when you are done removing the Slotting Top Plate, your 80% Lower should look like the image above which is a 100% complete and ready to use Lower Receiver…