News Reviews the Heavy-Duty Universal AR-15 80% Jig

Posted by

The All-New Modulus Arms Heavy-Duty AR-15 80% Jig has been shipping for a little over a month and the reviews are starting to flow online. has done reviews on our original Universal AR-15 80% Jig and has now provided a new review for the Heavy-Duty AR-15 Jig. conclusions for the Heavy-Duty AR-15 80% Jig are:

The second generation Modulus Arms Heavy Duty jig is a leaps and bound improvement over their original jig. While the original jig works perfectly well, and is as universal as the new jig, this version solves the usability issues that I believe the first one had. First, the jig is much, much more substantial in weight and material. Thick aluminum with steel inserts should keep this jig lasting a long time. Second, the greater surface area of the new top plate makes it much easier to use with a full-sizer router like I use. I no longer feel I need to use extra care to keep the router from tipping and causing unplanned damage to my lower. Third, the elimination of all of the seemingly endless need to assemble, disassemble and reassemble the jig for each step. The steel template inserts make configuring for subsequent steps a simple two or four short screw process. Fourth, the side plates have been made shorter and out of steel so they no longer test the limits of my drill press to fit it in place. Plus the steel makes it unnecessary to be concerned about wearing out the holes on the previous aluminum side plates. Some jigs are made of aluminum with steel drill guide inserts. Modulus Arms went further and just made the whole plate out of steel. I still think the jig should ship with a cotterless clevis pin rather than relying on installation of the front pivot pin or use of a bolt but that's a relatively small matter a simple $3 investment the end user can choose to make.

As with the first generation Modulus Arms jig, this jig is the only router based design that will handle some of the wilder lower designs out there. Specifically the New Frontier Armory lower comes to mind. This just won't fit in the Easy Jig even with the universal side plates. There's only so much universality you can build into a product that uses full side plates and this jig gets around that by only having partial length side plates.

View Comments

Modulus Arms Introduces the Heavy-Duty Universal AR-15 80% Jig

Modulus Arms is proud to present the Heavy-Duty Universal AR-15 80% Jig. This Jig is the answer to all the feedback that the customers have asked for. We have incorporated all the things we have learned and know about completing 80% lower receivers. The Heavy-Duty Jig is the fastest, most accurate, easiest and most durable Jig [...]

Read More »

ATF Clarifies Previous Ruling Regarding 80% Lower Receiver Manufacturing Processes

ATF Ruling 2015-1 ; Dated January 2, 2015General Synopsis:"Held, any person (including any corporation or other legal entity) engaged in the business of performing machining, molding, casting, forging, printing (additive manufacturing) or other manufacturing process to create a firearm frame or receiver, or to make a frame or receiver suitable for use as part of [...]

Read More »

New Package: Ultimate Builder's Kit

The Modulus Arms Ultimate Builder's Kit includes everything needed to get into 80 percent AR-15 and AR-308 rifles. Each of our Universal Jigs are included in the package, with which multiple lowers can be completed. For starters, we include a forged AR-15 and a billet AR-308 black anodized 80% lower. Our Jig Tool Kit, which [...]

Read More »

AR-10/AR-308 80% Lower Universal Jig Now Available

Modulus Arms would like to announce the release of our AR-308 / AR-10 80% Lower Receiver Jig. The MAJ-308 jig features the same universal compatibility as our highly popular MAJ-15 Universal AR-15 Lower Receiver Jig.Also like our Universal AR-15 Jig, only common tools such as a hand drill and router are needed to finish an [...]

Read More »

New Product Alert: Type III Hard Anodized Billet 6061-T6 AR-308 80% Lowers Now Available

80 Percent AR-308 Lower Receivers are now available for purchase at Modulus Arms. These billet lowers are hard anodized in various colors including black, blue, green, and our favorite, red! Visit the following link for further details and to view our entire current selection of AR-308 80% Lower Receivers.

Read More »

80 Percent Lower Completed Using Drill Press and Mini-Mill with Modulus Arms Universal AR-15 Jig

The Modulus Arms MAJ-15 Universal AR-15 80% Lower Receiver Jig was designed to be the easiest and most accurate Universal Jig on the market, requiring only a handheld drill and a common router to finish an AR-15 80% lower with absolute precision.To further highlight our Jig's versatility, a member of the forum recently completed [...]

Read More »

New Product Alert: 80 Percent Lower and Complete Upper Receiver Matched Sets

Modulus Arms has begun the release of matched set 80 Percent Lowers with Complete Upper Receivers. At the time of this release, bead blasted and black hard anodized finishes are available. We will soon release a variety of colors and finishes for our Forged 7075-T6 lower and upper receivers.These matched sets include a forged 7075-T6 [...]

Read More »

New Product Alert: MAJ-KIT-003 Front Takedown Kit

We have added a front takedown kit to enable the use of our MAJ-15 Universal AR-15 80% Lower Jig without needing a complete lower parts kit. Customers who do not posses a spare AR-15 lower parts kit are encouraged to purchase the MAJ-KIT-003 which includes the front takedown pin, spring, and detent.View and Purchase:

Read More »

Modulus Arms Recommended by Anderson Manufacturing as Best AR-15 80% Lower Jig

Anderson Manufacturing, makers of Anderson Rifles, has recommended the Modulus Arms Universal AR-15 80% Lower Receiver Jig as the best jig for an 80% Lower. Now in their 50th year in business, Anderson Manufacturing has manufactured parts for hundreds of thousands of AR-15 rifles. We are very proud and excited that Anderson Manufacturing has recognized the [...]

Read More »