• Front View of  Modulus Arms Heavy-Duty Universal AR-15 80% Lower Receiver Jig. Steel Parts.
  • Multiple Views of Modulus Arms Heavy-Duty  AR-15 80% Lower Receiver Jig. 80 Percent Ghost Jig.
  • Part layout and parts included in the Modulus Arms HD AR-15 80% Lower Receiver Jig.
  • Solid High Strength Steel Side Plates for the Modulus HD AR-15 80% Lower Receiver Jig. Wear resistant and durable.
  • Solid High Strength Steel Templates for all of the wear surfaces. Will last a lifetime.

Sale! Heavy-Duty Universal AR-15 80% Lower Receiver Jig

$219.99 $169.99
(You save $50.00)



Add a Lower Receiver to your purchase! Now 25% Off!

Traditional 80% Jigs use the fire-control area to align and center the Jig. Variations in the width of the lowers and inconsistencies in the forgings prevent this from being a repeatable place to locate the Jig. Other Jigs are incompatible with many different brands of lowers and do not account for manufacturing deviations and billet design differences. The result is poor fitment, improper location of machining features, sloppy fitment with upper receivers and the potential for non-functional rifles. Competitor's so called "Universal" Jigs do not solve these issues.

The Brand New Modulus Arms Heavy-Duty Jig takes a different approach, using standardized dimensions to locate and center the template. The Modulus Arms Heavy-Duty 80% Lower Jig uses the standard locations of the front take down and buffer tube mount to locate the Jig, resulting in a Jig that is compatible with any lower receiver, guaranteed.

At Modulus Arms, we have solved these lower receiver differences and applied them to our Heavy-Duty AR-15 80% Lower Receiver Jig. We have the most accurate, fastest, easiest, most durable and universal jig available. 

Key Features of the Heavy-Duty Jig:

Solid Steel Side Plates: Solid High Strength Alloy Steel Side Plates. We went above and beyond the competition and rather than using aluminum or even steel bushings we decided to make SOLID STEEL side plates.
Solid Steel Drill Template: Solid High Strength Alloy Steel Drill Template. The Heavy-Duty Jig has an increased thickness Drill Template that is made of SOLID STEEL. Oblonged holes and replacing pieces is a thing of the past.
Solid Steel Router Template: Solid High Strength Alloy Steel Router Template. Every wear surface of the Heavy-Duty Jig is made from High-Strength Steel. No more worn out templates or melted aluminum.
Easy and Fast Assembly: The Router Template and Drill Template are now held down with ONLY FOUR SCREWS!. This makes changing configurations for milling and drilling a breeze.
Larger Area Router Base: The Router Base is now MASSIVE! It is almost twice the size as the standard jig and is almost a full 3/8" thick.
Universal Compatibility: Use of standardized AR-15 upper dimensions to locate and center the Jig results in universal compatibility and more accurate machining.
Safer and Faster: The Modulus Arms Heavy-Duty AR-15 Jig accommodates the use of a router for safer and faster machining and only needs a  traditional handheld drill.
More Accurate: The Depth Gauge included  takes the guess work out of finishing your lower receiver minimizing the opportunity for mistakes.
Professionally Engineered Design: The Modulus Arms Heavy-Duty AR-15 Lower Receiver Jig is designed by a team of mechanical engineers with decades of experience and CNC machined to tight tolerances.
For Independent Reviews of the Heavy-Duty Jig checkout these links:
Kit Includes:

(2) Side Plates (High Strength Alloy Steel)

(1) Router Template (High Strength Alloy Steel)

(1) Drill Template (High Strength Alloy Steel)

(1) Rear Support (Al 6061-T6)

(1) Top Plate (Al 6061-T6)

(1) Front Support (Al 6061-T6)

(1) Drill Bit Depth Gauge (Al 6061-T6)

(1) Buffer Support (Al 6061-T6)

(1) Hardware Kit (Stainless Steel)

Recommended additions (Not Included):

Jig Fabrication Tool Kit

Solid Carbide End Mill Bit

Speed Drill for Hand Held Drills

AR-15 Front Takedown Kit



Product Videos

Modulus Arms AR-15 Jig Overview

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Product Reviews

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Previous | Showing reviews 51-100 of 151 | Next

  1. Works Great!

    Posted by Johnny McKenzie on 26th Jul 2016

    The jig is truly universal. I had tried two other jigs to work my 80% lower AR-9 and the Modulus Arms Heavy-Duty Universal AR-15 Jig finished the job!

  2. Don't Bother With the Other Modulus Jig

    Posted by Unknown on 25th Jul 2016

    After a year or so of contemplating I decided to tackle an 80. I was initially drawn to MA because of its ability to accept all 80's. Who wants to have an 80 the jig will not accommodate? I dropped the 150 for the universal jig. What a big mistake! After one 80, the drill guide becomes so distorted. I then ordered the heavy duty jig. I really like MA's design. The heavy duty jig is easy and durable. The parts that need to be strong and durable are made of steel. Let those who have ears hear. STAY AWAY FROM THE NON HEAVY DUTY JIG!!!! Spend the extra thirty dollars and get a product that you will be able to use more than once or twice. I had to learn the hard way. Quite honestly, I think MA should discontinue their original offering or at the very least sell them at a deeply discounted rate. MA got it right with the heavy duty jig but the original was a real disappointment and a waste of money.

  3. The Balls!

    Posted by Bill on 24th Jul 2016

    This is the balls! I have a couple other jigs and this one is far and away the best. I have an 80% Arms jig also and was trying to decide if it was worth switching to do my New Frontier Lower and wow I will never use that thing again.

  4. Two Words to describe HD Jig

    Posted by Danny M on 24th Jul 2016

    "GET IT!" I should have bought this one to begin with. I wanted to skimp out, save money, and buy one of the "less expensive" jigs. I was halfway through the process of drill ALL THOSE HOLES and my lower looked like a rat chewed on it! I figured it was toast. I sold the "other" jig and I bought the Modulus HD Jig hoping I could save it. People, this jig is THE BEST! BUY IT! it is worth every penny and then some. Helpful hint to make it a pure pleasure...sharp bits. I used a Sears Craftsman 28212 router. (one that was suggested on ARF com) BUY IT and you won't be sorry. And Yes, I was able to save the lower. Thanks Modulus!!!!

  5. Very Impressed

    Posted by John Colbert on 20th Jul 2016

    I have seen several different Jigs and read about many more. In my opinion none come close to the quality and craftsmanship to the Modulus Heavy Duty Jigs.

  6. Superlative Design Concept and Manufacture

    Posted by Robin Steal on 17th Jul 2016

    Doing my first build ever I knew a great jig would be needed and quite by accident stumbled onto Modulus Arms for the first time too. I'm just about to use the HD jig but know it's perfect for the task at hand. Browsing it at the site, looking at the videos and then the instruction manual I was pretty much sold on it because to do any job well the proper tooling is needed. Reading the reviews was the icing that cinched it for me. I can't comment on having used it but that doesn't matter because there is no way that I would be able to add anything positively new about it even if I already did that has not been already mentioned in other reviews on the HD Jig.
    All I can say is I concur with them. >:)

  7. Great Product!!!

    Posted by Ken on 14th Jul 2016

    Product worked as advertised. The system they supply you with worked out better than I expected. This was my first build and the only way they would have made it any better is them holding my hand. Thanks

  8. Super Tool

    Posted by Dave on 14th Jul 2016

    Very easy to use and I had no trouble getting a machine shop quality job...

  9. Great jig that will last through many builds.

    Posted by Adam on 8th Jul 2016

    The jig arrived super fast. The fit and finish of the pieces is very high quality. The jig worked great and should last a very long time.

  10. Tough piece of hardware

    Posted by Unknown on 5th Jul 2016

    What an awesome jig absolutely perfect, talk about heavy duty.

  11. Hassle Free

    Posted by Joshua Zientara on 30th Jun 2016

    This jig is heavy. You won't be cutting through it accidental. The instructions a clear and precise. I have had no difficulty using it, and I expect to be using it well into the future.

  12. Loving it

    Posted by Aaron B. on 30th Jun 2016

    Right out of the box it was easy to use. Quality steel alloy. Should get dozens uses out of the steel plates. I'm glad I invested on the better set. I'm practicing on a polymer lower. I learned quickly to go slow and take your time.

  13. It's well worth it

    Posted by Lt Dang on 29th Jun 2016

    The price may seem a bit high, especially with everything else you want to buy for your build, but as you assemble the jig you immediately appreciate how well it's crafted and the level of precision it brings to the process. It's well worth it. No regrets.

  14. very well constructed

    Posted by Thomas Hobbs on 28th Jun 2016

    Well built and easy to install. Great instructions as well. A definite must have if milling AR lowers

  15. great products as usually

    Posted by T. T. on 27th Jun 2016

    I have not used this product yet however, I have used the 308 jig many times with excellent results....I assembled the ar 15 jig and it is even easier than the 308....My hope is the 308 jig will evolve like the ar 15 ..... again great products

  16. Worked very well.

    Posted by Jason on 27th Jun 2016

    This is my first jig & 80% experience, so I have nothing else to compare it to.

    Worked out well.

    I believe that this is possible to do with a hand drill; but doing so requires a lot of patience. I tried it, because I wanted to know what it was like before recommending the process & product to friends. I lost my patience & did the majority of the drilling on a cheap drill press.
    Would probably do very well with polymer receivers.

    The end result is very accurate. No doubt that this jig accomplishes superior accuracy.

  17. Another whole-hearted endorsement

    Posted by Mark on 23rd Jun 2016

    Just completed my 1st lower (one of Modulus'), and I could hardly be happier with the HD jig. Extremely stable and strong (survived a 2 1/2 foot drop off the bench when its WD-40-soaked body slipped out of my hand on the way between the drill press and the router), and the approach to indexing the lower to the jig is perfect. The only suggestion for Modulus I have its to figure out some way to incorporate LEDs into the underside of the top plate to provide illumination into the pockets. For other first-timers: The key is being SLOOOWWW with the router -- mid-to high speed setting, but absolutely creeping along, *always* using clockwise circular motions, and always approaching the corners in many tiny circular passes until you reach the template to avoid chattering. Oh, and no matter how slow you're moving the router, move it slower!

  18. It's my only jig and first try and it worked

    Posted by musicman44mag on 22nd Jun 2016

    Simple instruction printed off the internet. The guide for drill depths was great but not the best for my 1983 craftsman router so i used a caliper to measure seat depths on the guide and checked it against the pocket.

  19. just plain works.

    Posted by Josh on 21st Jun 2016

    I'm very pleased with my heavy duty jig. I just completed my first 2 lowers with excellent results. I would not hesitate to recommend this to others or buy again! It's nice to get a solid, well made product that does exactly what it's supposed to do.

  20. best jig i've seen

    Posted by Clifford Yorke on 14th Jun 2016

    Jig's efficient design makes machining a lot quicker, if you plan on machining multiple receivers, this jig is well worth owning.

  21. best jig!! spend the extra money you will be happy you did!!

    Posted by Unknown on 12th Jun 2016

    I purchased both jigs, you will be very satisfied with the heavy duty jig, faster, less time switching from drilling to milling. Spend the extra money you will be happy you did.

  22. Best Option Out There

    Posted by Unknown on 11th Jun 2016

    This is the best option out there especially if you think you might end up using lowers from different manufacturers. Most jigs have compatibility issues but not this one. Great product.

  23. Expensive but worth EVERY penny!

    Posted by Gary on 10th Jun 2016

    Bought this jig due to its advertised build quality and material. I received it a short time after ordering. All I can say was, is wow! This thing is a gem and I cannot believe the attention to detail and how well thought out the design is.


    Posted by Red on 30th May 2016

    A friend of mine and I purchased this jig, along with lowers, but we haven’t milled a lower yet so this review is of the jig’s fit & finish only.

    Right out of the box we were impressed. The entire jig, in its plastic, bag had some serious weight to it. The side plates & drill guide are thick steel with radiuses everywhere you can think of. NO burrs, machine marks or sharp edges. The router base and end pieces are of the same high quality fit & finish machined from high quality aluminum.

    The drill guides fit into the router base is secure with NO play and is held in place using four counter sunk SS screws. It shouldn’t move or vibrate while drilling.

    Next we assembled the jig on a lower and assessed the fit. My friend has some machining experience and liked what he saw. Sides are parallel and there is a SS screw between the side plates, near the bottom, that precludes them from moving inward when clamped in a machine vise.

    Summation: tolerances are very tight and machining is highly accurate.

    All & all, this jig is a great piece of workmanship thanks to the engineering staff at Modulus Arms. They have done their homework so we don’t have to.

  25. Best and easiest jig on the market

    Posted by Kirk on 23rd May 2016

    I built a LR 308 last year with their jig and it turned out marvelous. This year I am building an ar 15 with the 80% lower platform. I am expecting the same great results with their heavy duty version. I would definitly recommend this jig to everyone.

  26. easiest jig to use

    Posted by Unknown on 23rd May 2016

    Your step by step instructions made this so simple and easy the hardest thing about this was keeping my excitement down so I had the patience to complete the task great product Thanks

  27. Outstanding product

    Posted by AndyM on 22nd May 2016

    Purchased jig a month ago and just looked at it while waiting on drill press. Assembled lower to jig in about 15 minutes following instructions. Took about 20 minutes to drill all holes. Used Kroil lubricant. Then mounted jig into bench vise. Routing took about two hours but I took my time. Set up shop vac with homemade adapter to suck milling paticles from side of jig. Driilled the holes for the pins ect. Assembled lower assembly without issue. Following instructions I think anyone should be able to get the job done.

  28. happy customer

    Posted by nate on 16th May 2016

    I am very impressed with this jig. It is heavy duty and high quality. I did a lot of research before purchasing a jig and I decided on this one because I wanted a jig that would last a long time.. And one that is fairly easy to use.. Well this jig is all that. It is a little expensive compared to others but it is a superior jig to..I would definetly recommend this product to someone and I would definetly buy it again..

  29. happy customer

    Posted by nate on 14th May 2016

    I am very pleased with this jig.. It is exactly as it states.. Very heavy duty almost entirely made of steel. Very easy to use.. A touch on the pricey side but you get every Penny's worth with the heavy duty jig... I would definetly recommend this product to anyone looking for a long lasting high quality jig...

  30. Looking forward to trying it out.

    Posted by Don on 7th May 2016

    This appears to be not only the best thought out jig but perhaps the only well thought out jig. Everything about it makes perfect sense - design, fit, finish and materials.

  31. Best jig out there

    Posted by Shawn on 3rd May 2016

    I own both the Universal jig that you see everywhere else and they do work but the Modulus Arms Heavy-Duty Universal AR-15 Jig is by leaps and bounds a better design and more durable than the other jigs out there. If you are looking for an AR-15 80 percent lower jig this is the only one you should be looking at.

  32. Great improvement to an already great jig

    Posted by ES on 3rd May 2016

    This is such a great improvement. Can't wait to do more receivers. The older AR15 jig was vastly superior to anything else I have used, but the new and improved jig is even better. I couldn't be happier with my purchase. Best money spent in a long time.

  33. What a difference!

    Posted by Tom McQuerry on 2nd May 2016

    I have done the polymer lowers, and aluminum lowers with both the included jig (polymer) and a standard sandwich aluminum jig. This jig made the job look so clean that the only way to tell it wasn't a 100% lower to begin with was the silver color where it was cut. The upper fit perfectly (not sloppy like the sandwich jig) and the trigger slot was dead centered. I used a Ryobi router from Home Depot and it worked fine (cheapest router they had).

  34. Will save you money in the end.

    Posted by Unknown on 2nd May 2016

    I started out with a "standard" jig from another manufacturer. Wasted 2 blanks and seriously struggled with a dangerous setup. I'm not some kind of klutz, I routinely build far more complicated stuff. I have above-average tools with a nice drill press and vises. First cheapo-jig attempt was a complete fail. Second attempt "worked", but not something you'd be proud to be seen using. Extremely amateurish, crooked and just a poor quality result. This jig is the real deal. Perfect first time, at least 3 times as fast as suffering through producing garbage with the other jig. AND, it fits every type of lower blank because it uses the same reference points that the upper does. I defy you to tell the difference between my first lower made on this jig and one that is done by a factory. So I wasted two lower blanks, the cheaper jig and a TON of time when I should have just gotten the proper one first. About $150 and many hours wasted in all. Luckily I still have all my fingers. I'm a tightwad and as usual, I cheaped it out at first and ended up spending more in the end. Could have bought this and been money ahead. Now all of my buddies will use this to make theirs as well. Do yourself a huge favor and just spend a few extra bucks to get this one.

  35. Heavy Duty Jig

    Posted by TA on 29th Apr 2016

    I owned their original jig and upgraded to the heavy duty. The original was good, this is by far the best upgrade and the best jig on the market. I've already completed several lowers using it. It is worth your money. Please make a .308 heavy duty jig.

  36. Well made, great design, A#1

    Posted by Frank on 28th Apr 2016

    I researched hard and bought this jig first. As a novice the first lower I milled worked! I found the instructions vague and watched the videos and got it right. Showed the jig to a machinist friend and said it was well made!!

  37. Product looks great

    Posted by GT on 27th Apr 2016

    Only gave it a 4 because I haven't used it yet. I have assembled it on a lower and I do not see any issues. Everything looks as advertised. What I would like to see is a slightly smaller insert for roughing out and then use the actual size needed for your final router pass. I would pay a few extra $$ for that option. I'm sure once I use this the rating will be a 5. By the way, it does fit on a New Frontier lower as stated.

  38. Great design

    Posted by Ben on 27th Apr 2016

    Max did it right. One day (long day) complete mill to build out of lower. Had upper on by evening. Can't wait for more builds. My military buddies want to do builds now after seeing ease of use with this jig.

  39. An amazing product!

    Posted by Ryan N. on 26th Apr 2016

    I bought this jig after many long hours of research and I'm happy I did. I consider myself to be mechanically inclined but had no prior machining experience. This product is top quality and made my first go at completing an 80% lower a breeze. I couldn't be more exciting to cover myself in metal shavings over and over again! Thanks Modulus Arms for delivering quality products and service. Future buyers be sure to pick up the Dewalt model 611 router which is the newly recommended router by Modulus. It's worth every penny. As a side note, I would love to see an updated video from Modulous Arms on the milling process and recommended tools so new users can avoid any confusion.

  40. Over all, a great product

    Posted by Isaac Madera on 25th Apr 2016

    This is a fantastic jig over all. Very simple to use and very high quality. As for constructive criticism, it is one of the most expensive jig's on the market (I purchased the AR-15 heavy duty)

  41. best jig kit

    Posted by John Harte on 21st Apr 2016

    Works great fit both polymer and forged lowers from different companies.Easy use and finished product worked flawlessly.

  42. great overall product.

    Posted by Unknown on 18th Apr 2016

    I love the jig. It assembled very tight. The only thing is. It would be nice to include a printed set of instructions. That way I wouldn't have to down load and print. Second thing the trigger slot is different than the video shown on the instruction video. Other than that, great product.

  43. Best setup used .

    Posted by Unknown on 13th Apr 2016

    Like the way it is constructed and a breeze to assemble. Very nice to use a router on it to get better looking results without lots of manual filing. This design is far more superior than others I have used. Very nicely packed and quick delivery. Looking at ordering your 308 jig.

  44. Must have for New Frontier Lowers

    Posted by RHR on 12th Apr 2016

    Mag well on the New Frontier Armory 80% Billet lower is wider than spec and most other jigs will not work. Not a problem with this jig! Just completed my third and no issues yet. I like the steel template inserts. Have burnt into the aluminum templates with end mills on other peoples jigs. No problem on this one.

  45. Hands Down, The BEST JIG Money Can Buy

    Posted by Marco on 11th Apr 2016

    I sold my 80% Arms Jig and gave this new Heavy Duty Jig a try. It was the best decision I every made. The 80% Arms had limitations to the kind of 80% paperweights you could mill out with it. Since I've purchasing this jig, I've been able to mill out all sorts of lowers, from billet lower receivers to 9mm glock mag lower receivers. Also, once you've set up the jig, it's easy to switch from milling the main trigger pocket, to the rear pocket, and to the trigger hole. I hightly recommend this superior product.

  46. The JIG that sets the standard!

    Posted by Capt. J on 11th Apr 2016

    This is by far the best jig to use for the proper milling of an 80% lower receiver. Weather your using a drill press (not recommended) Router (better then a drill press) or a Minnie Mill (Highly recommend) your finished lower will be at proper specification. By fixing at the take downs and tube threads you have the ability to mill any manufactured lower available. This is do to the standard measurements of these points. The plates on the Heavy Duty JIG will last indefinitely with proper care where aluminum plates will fail over time. Buy this and don't worry about the various fitment issues, this is a well thought out and engineered tool. Modulus arms set the bar with this jig.

  47. The best..period.

    Posted by Curt on 9th Apr 2016

    If you want your build to go right the first time, evertime, this is it. We have done both 7075 and the polymer lowers with the Modulous Heavy Duty Jig. Order your lower, pull the jig it came with off, throw it in the trash and slap it in the Modulous, period.

  48. Love this design

    Posted by Unknown on 6th Apr 2016

    Definitely more complex that standard jigs, but once set up, this thing just works great. I borrowed a friends jig for my 1st lower and after a couple of passes for the trigger pocket, I could see that prior use had chewed up the guide and things were looking a little ragged. On the Modulus, the space between the jig top and lower, (which requires an extended end mill) eliminates chewing up the jig. So after machining 3 lowers, the thing looks brand new. A really great design. Pricey? Yea... but like any quality tool, the Modulus jig will pay big dividends in the end. Especially if you're going to build multiple rifles.
    Quit looking around and just buy the Modulus Jig!!

  49. great jig, very easy to use.

    Posted by Josh Barrett on 31st Mar 2016

    Finished my first lower with this jig in 2 hours, worked great, no problems. Lowers have all turned out perfect.

  50. instructions?

    Posted by John Bell on 27th Mar 2016

    First off, the jig is very nice, easy to assemble, and accurate. The quality is excellent. So why only 3 stars? As persnickety as this sounds, including instructions with your product is basically expected by the consumer. I understand very detailed and easy to follow instructions are on the website. However, I would either have to print off 21 pages of color instructions or take my laptop to the work area. Neither of which I want to do.

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