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Universal 80 Lower Jig - RJ556U for Mil-spec AR-15 80% Lower Receivers by Polymer80

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This jig is compatible with our Forged 80% Lowers. Our Premium Fire/Safe Marked Billet 80% Lowers are not compatible with this 80% lower jig. Other manufacturer's billet 80% lowers may compatible with this 80% lower jig, provided their lower receiver design adheres to mil-spec specifications.

Additionally, while this jig can be used to finish a lower for use with the 9mm caliber, a standard-sized lower must be used coupled with a 9mm conversion kit. The jig will not accept our own 9mm 80% lowers.

Most 80% jigs are made of precisely-machined alloys, made rugged enough to cut and drill lower after lower. If you’re the once-and-done builder (or you’re working on a tight budget), you’re probably looking for something simpler. Maybe you just want to try out gunsmithing at home and don’t want a big sunk cost. We get it. That’s why we partnered up with our friends at Polymer80 to offer you a new disposable, universal AR-15/AR9 80 lower jig!

The RJ556U jig is made from reinforced polymer and ships with the necessary drill bits and end mill bit to cut and drill any mil-spec AR-15 or AR9 80% lower receiver. This jig’s tough nylon composite allows it to reliably machine polymer and forged or billet aluminum receiver blanks - up to three with the original tooling. All for a super-low price.

The RJ556U Jig Includes:

  • (1) Left and Right Side Plate
  • (3) Trigger Template Guides
  • (1) 9mm HSS End Mill
  • (1) 5/16 Drill Bit
  • (1) ⅜ Drill Bit
  • (1) 5/32 Drill Bit

Cutting and Drilling with The Jig

The RJ556U Jig doesn’t require an expensive mill to operate. All that’s required to use the jig is a standard drill press and some basic measuring devices:

  • Vise For Drill Press - 6” jaws
  • Drill Press -1850-2250 RPM
  • Digital Calipers
  • Dremel Bit #9904
  • Bubble Level
  • Round Machinists File
  • Non-marring Vice Jaws
  • Lower Receiver Vice Block
  • Upper Receiver Vice Block 

Learn how to cut and drill your receiver blank by downloading Polymer80’s written instructions here.

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Shipping Restrictions

Shipping of various parts and/or accessories are prohibited to states and locales (ie New Jersey, California, New York, etc…) with restrictions against certain parts and/or accessories or "assault weapons" (i.e. states with high-capacity magazine restrictions, manufacturing of semi-automatic weapons, etc..). It is your responsibility to be aware of your local firearms laws before purchasing from our website or machining a firearm. We try our best to keep our shipping page current, but laws change daily. only ships within the United States. Federal legislation dictates we cannot ship our products internationally.

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We are a national retailer of individual components and not all products depicted on this website are legal in every state. Shipping of various products found on this website are prohibited to some states (such as California, Connecticut, District of Columbia, Hawaii, New Jersey, New York, Rhode Island, and Washington). The information, pictures, text or products presented on this website are not a representation by us, and should not be understood by you, that any product or completed firearm is legal to assemble or own in your state of residence. We encourage each and every builder to perform their own research about the state and federal laws that apply to them. It is your responsibility to understand the law and we encourage you to consult with an attorney or your local ATF representative.