• 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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Showing reviews 1-50 of 151 | Next

  1. Great Jig

    Posted by Matthew on 16th Mar 2017

    I am very pleased with this jig. Easy to follow instructions! You need a good drill that spins really straight. My crap drill opened up the guide holes because it didn't spin straight.

  2. hands down the best jig on the market

    Posted by Jason shepherd on 12th Mar 2017

    As long as you take your time and do each step right you will end up with a lower that looks like you did it in a mill. And it will be fully functional and look amazing. Thank you so much for this awesome product. You have a life long customer now modulus arms.

  3. Great AR15 jig

    Posted by Dave on 7th Mar 2017

    I bought a 80 percent arms jig last year and used it on a Anderson 80 percent lower. I followed their directions and made no mistakes only to end up with a non functioning lower. I called the customer service line and they told me to drill the trigger pocket deeper but the problem was it was deep as there gauge using the drill stop collar. I ended up selling that so called universal jig and figured I just had an expensive paper weight. I saw the Modulus arms jig and saw how much better it attaches to any AR lower. I ordered it along with one of their 80 percent lowers. Before I took my chances drilling and milling it out I attached it to my already milled Anderson lower. I figured there was no way that it should of took any material off seeing it was already done and to my surprise it took off little out of that trigger pocket and quite a bit out of the trigger hole in bottom of the lower. I installed a parts kit and it functioned right off the bat. I was so happy that this truly does work on all lowers. I proceed to mill out the lower that I bought with the modulus jig and it turned out perfect and fully functional. Super happy with this jig and will be using it many times to come. Thanks for a great product!

  4. To Easy

    Posted by Larry Chapman on 5th Mar 2017

    This product makes the job as easy as ABC.. very straight foward

  5. worth every penny and some.

    Posted by Gregory Sevigny on 3rd Mar 2017

    I have access to a full machine shop but purchased this kit because I thought it would be a fun project to complete with my kids. Was skeptical about using a router with an endmill. To my amazement it worked great. Made one receiver with a dewalt trim router and another with my plunge. Used plenty of coolant along with a vacuum and endmill stayed clean and cool. Was amazed at how accurate the side holes came out using a drilling jig. Measured at work with a microheight on granite surface plate and they were within several tenths of what my print called out. I did however use the jig to only spot the holes and drilled and reamed on drill press once removed. If you want a machine shop end result on a budget you can't go wrong with this jig. Extremely well made all around. Can't wait to bang out a couple more.

  6. works way better than 80 percent arms jig

    Posted by David Southwood on 2nd Mar 2017

    I bought a 80 percent arms jig last year and used it on a Anderson 7075 lower and it was non functioning after I followed their directions to a tee. The trigger group would not fit nor work correctly. I immediately sold the jig since they didn't back the problem's I was having and there customer service sucked. I recently discovered the modulus arms heavy duty jig and went ahead and ordered it after talking to their customer service dept. Before I ordered. They were very helpful and I could tell the jig was far better design by how it attaches to the 80 percent lower no matter the brand. When I received the jig I also ordered one of there 80 percent lowers but before I milled it I figured I take a chance of trying it on my paperweight Anderson lower that was messed up from the 80 percent arms jig. To my surprise it milled quite a bit of material for what should of been a finished 100 percent lower. It opened up the trigger hole in lower of receiver and some of the walls of the trigger housing. I was able to make that lower a fully functional ready to use part. Very happy with the modulus jig and will be long time customer of theirs. Hands down best 80 percent jig on the market!!!!

  7. Well crafted...

    Posted by ground(ed)radio on 20th Feb 2017

    Can't remember when I had so much fun chippin' and drillin' metal. This jig is solidly built and well crafted. You will be happy to learn that the designers actually thought it all out.
    Using a Makita RT0701C, I found the size of router base to be perfect. The templates are top notch; and if your doing the tracing right, they are none the less for wear.
    I would recommend this to a friend...and anyone wanting to do more than one lower.

  8. excellant product !

    Posted by Unknown on 18th Feb 2017

    Well made product excellent machining, easy assembling and not to many steps to change in process,

  9. Review from WEP

    Posted by William E Pacetti on 11th Feb 2017

    Very well built, strong. I have finished drilling all of the holes, waiting on my end mill. Will finish this week.

  10. Very Nice Jig (AR-15 HD Jig)

    Posted by Mario V. on 8th Feb 2017

    Although this is my very first jig, comparing the Modulus Arms AR-15 HD-Jig to some of the other flimsy looking units tells me this HD-Jig is a tank that will be used for many years. The solid construction, with steal parts where it counts, locks and centers any 80% lower in place. My first drilling and milling job came out very professional looking; there were no errors or sloppy surfaces. Every part that was tooled on the lower was precise and smooth. I would highly recommend getting the Speed Drill Kit, as that will drastically cut down on the time for those 3/8" holes. After drilled the 1/4" holes in 1-2 minutes for each hole, it took only 15-20 seconds for each 3/8" hole. I used an electric drill, since the battery in my cordless drill holds a small charge. The drilling operation took less than half an hour. But I did take my time with the milling, making 20 or so passes to completion in about two hours on top of the drilling phase.
    I definitely recommend this jig over others, even if it costs a bit more, since it's 100% compatible with all the lowers out there.

  11. Get one you want regret it

    Posted by Unknown on 7th Feb 2017

    After ruining one AR-15 80% lower receiver and getting off to a bad start on another receiver I decided to purchase Modules Arms Heavy Duty Universal Jig Set after reading some great reviews about it. Following the jig instruction I was able to complete and save the lower receiver which I got off to a bad start with after using a different jig. The results were great. The jig is simple to use, follow the instructions step by step and purchase a long 1/4 mill bit with 3/4'" cutting surface you to will produce professional results also. I have started a second receiver with gained confidence it will turn out as well as the first on did.

  12. Top quality jig

    Posted by Unknown on 30th Jan 2017

    Jig is built with exceptional quality. It's easy to use and does an incredible job. Well worth the money.

  13. ar 15 jig

    Posted by Donald Wehage on 26th Jan 2017

    This is the 2nd one I have bought. I built a ar10 and now building a ar15 best jigs on the market as far as concerned

  14. best out there!

    Posted by veronica condon on 16th Jan 2017

    I have many jigs over the years including 80% arms easy jig and this product is hands down the best on the market. I love it and look forward to many years of use. Thank you modulus arms.


    Posted by Unknown on 7th Jan 2017

    This made for a simple lower completion. I had never done one before. The videos online are outdated or do not apply to the heavy duty version. However there is a great one on ar15.com to follow. I completed one in 3 hours. Being a complete newb. It took some time to figure out the jig. Again there is no instructions that match this jig exactly. But I would buy this again in a heartbeat.

  16. Perfect jig

    Posted by Charles W. A. on 23rd Dec 2016

    Just finished my first lower. It looks great, kept everything to milspec. I would highly recommend this to anyone of any skill level. Can't wait to mill a few more. WELL DONE MODULUS ARMS!!!!

  17. Heavy Duty Jig

    Posted by Unknown on 2nd Dec 2016

    I haven't had a chance to use this jig yet, but I can't wait to try it out. After hours of research of available jigs, I decided on this one because of its construction, steel vs aluminum, should be good for many uses.

  18. truly great design and workmanship

    Posted by john constable on 29th Nov 2016

    I couldn't be happier with this jig. I don't know what more to say.
    The design is superb and simple at the same time. No surprises in putting it together or using it.
    The instructions were clear and concise but I did a lot of on-line reading as well.
    I have s 1/2 hp drill press but still used the speed drill just to save additional wear on the drilling block.
    I used the Makita router with good results.
    I totally recommend this product and will probably buy the heavy duty AR-10 jig at some point.


    Posted by buddy lang on 16th Nov 2016

    Just follow the guide and the end result will be great

  20. Happy I bought this.

    Posted by Steve Silliman on 8th Nov 2016

    Used this on my third lower. By far the quickest I have completed one so far and I'm sure the next one will be faster.

  21. outside the box

    Posted by Unknown on 8th Nov 2016

    First off let me say I havent cut the lowers yet. I'm fortunate to have a manford mill so my experience will be different than others. This is the best of jigs I've seen. It's the only one that align correctly on the correct axis. It's a tad more bothersome to set up but it registers the lower correctly.The use of a drill press and carefully centering the bit will greatly increase jig life. Also if your using a drill buy there pilot bit. Quality is A+

  22. Well Thought Out Jig!

    Posted by Ron on 6th Nov 2016

    This is a very well thought out versatile jig for completing a lower 80% receiver. The quality of the jigs craftsmanship speaks volumes in the attention to detail. It's well made, and does exactly what it is designed to. The instructions and videos make this idiot proof when you follow the instructions. I couldn't be more pleased! Excellent quality, excellent service, and fast shipping.

  23. Nicely made jig

    Posted by Unknown on 2nd Nov 2016

    I used the jig for my first build today. The online instructions are great. Easy to assemble and use. I can for see using this jig for a long time.

  24. really nice jig

    Posted by Matthew Meizinger on 2nd Nov 2016

    Nice tight fitting plates. Heavy duty so accidents won't happen.

  25. Great Jig.

    Posted by Unknown on 30th Oct 2016

    Haven't used it yet but it if looks could kill this would end lives.

  26. outstanding

    Posted by Unknown on 29th Oct 2016

    First time and all went great.

  27. Fantastic

    Posted by Chris on 19th Oct 2016

    This jig is great! Took this on as a project and I'm very happy that I decided to go with Modulus Arms! I've seen some horror stories of other jigs but this one made everything easy and the lower came out almost perfect! Couldn't be happier with the purchase and now that I got my "learning" down, I think my next one will be even better!

  28. Excellent jig!

    Posted by Satisfied Customer on 29th Sep 2016

    I purchased this jig having never worked on an 80% lower before, expecting to be able to finish the job with a router and hand drill (I used a drill press for all of the holes). I had also never worked with metal on a scale like this, especially the milling aspect. I have to say, this jig delivered on helping me to achieve excellent results. All of the milling and holes spec'd out correctly. My results would have been even better if I had started out with a decent router. I ended up purchasing the Ridgid 24012 recommended in the instructions (register it online after purchase to receive a Lifetime Service Agreement on it) and received a 10% discount for being a veteran to boot.

    My workspace might have been too high, but I will say that I had an extremely difficult time trying to see into the milling area while working, so I ended up doing nearly all of the work by feel. This contributed to an extended length of time that it took me to complete the process. That's not such a big deal since I will not be mass producing these lowers. Now that I'm familiar with the assembly of the jig and how the process flows, future jobs will not take as long (as is usually the case).

    The jig shows no wear after my first use.

  29. If your on the fence already, just order it!!

    Posted by Tyler S on 24th Sep 2016

    great kit! Top notch quality for sure. I have completed other lowers on drill press style jigs i modified to use a router, none have come out as clean as it did with the modulus jig!

  30. Solid as a rock! (if not more...)

    Posted by John Heck on 21st Sep 2016

    I had been going back-and-forth looking at different jigs on the market and many of the other manufacturers that I researched appear to be putting out products that are more or less disposable. Most of them are designed for one time usage and feature plastic or polymer plates with reinforced holes and apparently after they get used a couple of times the Jigs start to wear and breakdown. I wanted to purchase this jig once and plan on making it last a lifetime. I am extremely happy with the modulus Jig and would recommend it to anyone. You can certainly find cheaper jigs on the market but always remember that you get what you pay for.

  31. Great Jig!!

    Posted by Darrell Barham on 19th Sep 2016

    This is one solid jig! It is easy to assemble, easy to use and has replaceable parts. I have used this jig with both handheld power tools and a drill press, it worked great.

  32. great product

    Posted by Robert Baker on 14th Sep 2016

    It is exactly as described on the website and in the videos I have seen. I look forward to getting a lot of use out of it. Order was processed quickly and delivery was 2 days from California to Maryland. Not a single complaint. Thanks for a good product and better customer service.

  33. Great jig

    Posted by Eduardo on 12th Sep 2016

    This jig made completing my lower easy. Once is assembled its solid.

  34. The beast of all Jigs!

    Posted by COMMI-fornia on 5th Sep 2016

    This was the best decision I've made by far in terms of protecting my 2A rights! I was amazed at how fast and easy it was to do my first 80% lower and by using the HD jig pretty much took all the guess work out. This thing is a beast and took little to no abuse from my router and hand held drill. Instructions were easy to comprehend and follow with illustrations to help. This truly is a UNIVERSAL jig as I was able to crank out a billet lower and then switch to doing a polymer lower with both end results coming out flawless! Would not hesitate to repurchase if/when that time comes....

  35. Very solid and usable.

    Posted by Chris on 4th Sep 2016

    The product is bullet proof. Would have given it 5 stars, but the downside is that it requires a 4" end mill bit and for the price it should come with one. I am currently waiting to have one delivered so I can finish my project.

  36. The Easist Jig on the market.

    Posted by Unknown on 2nd Sep 2016

    I have used many different jigs including drill press jigs and hand drill jigs. This one takes the cake! Definitely the easiest and fastest one I've used to date. Assembling the Jig to the lower took less than 5 minutes. The heavy side plates provided more confidence when Drilling the safety selector and Fire Control pin holes. Changing out from the hand drill collar to the router collar was so easy it only takes 30 seconds.

    Other than that I will be recommending this jig to all my friends and family, great job and keep up the good work.

  37. Great!

    Posted by chris on 29th Aug 2016

    The jig is great and easy to use

  38. Heavy Duty Jig

    Posted by steve on 29th Aug 2016

    I plan open using this jig to its full potential fabricating multiple lowers

  39. Excellent product!

    Posted by Eric Brannon on 22nd Aug 2016

    I recently used this jig to complete a Hellfire Armory 80% lower receiver and I am very impressed with the results. This jig is very well thought out and super stout. I've got access to a manual mill at work but decided to use all hand tools to see how it would turn out. Using a Ridgid laminate router and a 20v cordless drill with this jig I turned out a lower that was as good or better than those I've done on a mill. I definitely recommend this product. Thanks guys for an awesome product!

  40. high quality jig

    Posted by BRADLEY M ESTEP on 18th Aug 2016

    worked great ! couldn't be happier with prodict

  41. Cream of the Crop

    Posted by Logan on 15th Aug 2016

    If you are serious about finishing your lower, and do not have access to a true machine shop, this is the way to go. The quality of the parts is top shelf. It is also very convenient to use without requiring complete disassembly between every step. The cost may seem high, but if you respect the jig and use it properly, it will last several lifetimes.

  42. excellent

    Posted by satisfied customer on 15th Aug 2016

    Works just as it should. Quality equipment.

  43. Rock Solid Jig!

    Posted by Unknown on 12th Aug 2016

    This isn't your average jig. No plastic parts here. Completes heavy duty metal from top to bottom and no cheesy screws either. Tighten, Drill, and Mill with confidence.

  44. Impressed

    Posted by Mike Rachwitz on 4th Aug 2016

    Being a retired tool and die maker I can tell quality in workmanship and finished product. this jig excels in design, fit, and finish. I was very impressed with the way everything fit and having hardened steel inserts should give it many years of usable life. Love the quality

  45. great jig

    Posted by jon drake on 3rd Aug 2016

    first time making a lower. i am a union sheet metal worker so i am familiar with the tools involved. this jig is heavy duty and will most likely make several lowers. making a 80 percent lower is a great project. yes you can buy an already made lower for about the same price, but this is alot more interesting. if you take your time you will have a quality lower that you can anodize yourself! this product from modulus arms makes it all happen!

  46. Fast shipping. Awesome Product

    Posted by Unknown on 3rd Aug 2016

    The HD Jig is awesome and came in 2 days.

  47. Well made jig

    Posted by Doug on 1st Aug 2016

    Being new to the 80% world, I researched a lot of jigs and finally settled on this one. I'm glad I did. This jig and instructions made the process Easy! The jig is very well made and the results were flawless. The only thing I wish Modulus would do is update their YouTube videos to reflect this new Heavy Duty model.

  48. Outstanding products!

    Posted by Everett on 29th Jul 2016

    Superbly designed and very well made. Should last for a long time and allow production of several more lowers in the next few years.

  49. Better than stated.

    Posted by Unknown on 26th Jul 2016

    Awesome jig. Did exactly what it was supposed to do, and did it better than I expected. Would of gave 5 stars, but it did not just Finish my lower by itself. So 4 stars it is.

  50. Really is heavy duty

    Posted by Elvin Hedddings on 26th Jul 2016

    I was impressed how tight everything fit together.
    Made for a very easy and precise milling job.

Showing reviews 1-50 of 151 | Next