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Modulus Arms AR-15 Instructions Manual

Universal 80% lower receiver jig
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Universal AR-15 80% Lower
Receiver Jig Instructions

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Summary of Contents for Modulus Arms AR-15

  • Page 1 Universal AR-15 80% Lower Receiver Jig Instructions...
  • Page 2 March 25, 2015 Modulus Arms Jig Contents The Modulus Arms Universal AR-15 80% Lower Receiver Jig contains the following parts: 1x Template 1x Depth Gauge 2x Side Plate 14x Screws [8-32 x ½”] 1x Drill Guide 2x Side Plate Screw [8-32 x 1.5”] 1x Front Support 10.
  • Page 3 March 25, 2015 Required Tools The following items are required to finish the 80% AR-15 Lower Receiver: (Available for sale on Modulus Arms Website) ¼” Dia, ¼” Shank, 4” Long, 1” Cut, Square End Mill 3/8” Drill Bit 19/64” Drill Bit 5/32”...
  • Page 4 Modulus Arms AR Lower Parts Kit may be used. Optionally, Modulus Arms offers an AR-15 Front Takedown Kit for sale on the website. To install the Front Support you must first install the front takedown pin. Next, you place the front support in the proper location and secure it with the front takedown pin as shown in Figure 4 (Right).
  • Page 5 Template: Align the template over the rear and front support as shown in Figure 7. Use four ½” screws to attach the template. Tighten all four screws to 1 ft-lb. Tighten rear support screws to 1 ft-lb. Figure 7: Template Attachment www.ModulusArms.com | AR-15 Jig Instructions...
  • Page 6 Note: It is recommended to put masking tape or some other protection over the sides of the lower before installing the side plates. Doing so will help prevent scratches or wear. Leave Loose Figure 8: Side Plate Alignment Squeeze then Tighten Figure 9: Side Plate Tightening www.ModulusArms.com | AR-15 Jig Instructions...
  • Page 7 This is true for all drilling of the lower.  Note: Use plenty of WD-40 or cutting fluid and remove the chips regularly. This is true for all drilling of the lower. Figure 11: Trigger Slot Holes www.ModulusArms.com | AR-15 Jig Instructions...
  • Page 8 Figure 13. Be sure to drill to the depth specified with the drill stop and do not go any further.  Note: Modulus Arms forged lower receivers have some of the rear pocket already machined. You must only drill the hole closest to the trigger slot template. ...
  • Page 9 SPINNING. THIS IS DANGEROUS AND THE MOST COMMON CAUSE OF BROKEN END MILLS OR DAMAGED JIGS/LOWERS.  Note: Be sure the end mill is very tight in the router. Tighten it as much as possible. www.ModulusArms.com | AR-15 Jig Instructions...
  • Page 10 This build up can be removed from the end mill with sand paper. Use of a cutting fluid or WD-40 is recommended. Figure 15: Trigger Slot Depth Setting www.ModulusArms.com | AR-15 Jig Instructions...
  • Page 11 March 25, 2015 Figure 16: Trigger Slot Router Placement Figure 17: Second Depth Mark www.ModulusArms.com | AR-15 Jig Instructions...
  • Page 12 The holes open to the trigger slot do not need drilling. The partial covered hole does not need drilling.  Note: Be sure the drill stop is tight. Check the placement of the drill stop with the depth gauge after each hole. www.ModulusArms.com | AR-15 Jig Instructions...
  • Page 13 Start the router and allow it to come completely up to speed. Start to move the router removing material. Start by moving in semi-circular motion in small clockwise steps. Press www.ModulusArms.com | AR-15 Jig Instructions...
  • Page 14 This build up can be removed from the end mill with sand paper. Use of a cutting fluid or WD-40 is recommended. Figure 22: End Mill Depth for Fire Control Pocket www.ModulusArms.com | AR-15 Jig Instructions...
  • Page 15 Milling the Rear Shelf Pocket Note: If you bought a forged lower from Modulus Arms, you can skip to Drilling the Hammer, Trigger and Safety Pin Holes. If you have a lower receiver that does not have a pre-machined rear pocket, you must continue with this section.
  • Page 16 This build up can be removed from the end mill with sand paper. Use of a cutting fluid or WD-40 is recommended. Figure 24: Depth Gauge for Rear Shelf www.ModulusArms.com | AR-15 Jig Instructions...
  • Page 17 Note: The extra holes below are there because the side plates and universal. They give you two times the amount of holes for drilling so you do not need to replace your side plates from premature wear. www.ModulusArms.com | AR-15 Jig Instructions...
  • Page 18 Note: Be sure not to start spinning the drill until after the drill bit is placed into the drill guide or premature wear will occur.  Note: Use plenty of WD-40 or cutting fluid and remove the chips regularly. www.ModulusArms.com | AR-15 Jig Instructions...
  • Page 19 Note: The extra holes below are there because the side plates and universal. They give you two times the amount of holes for drilling so you do not need to replace your side plates from premature wear. Figure 28: Trigger Pin Hole Figure 29: Hammer Pin Hole Done! Go Shooting! www.ModulusArms.com | AR-15 Jig Instructions...

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