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QD Barrel System for Lima-Six Upper (Page 1 of 2)
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Posted: 5/31/2026 8:05:52 PM EDT
[Last Edit: OFG_Can_Man][Edited]
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Some friends who are working on different projects encouraged me to get on here and post some of the stuff I have been playing with. To preface, my name is Jim Ryan, and I am one of the original founders of GemTech. Some of the older guys will know me. Back in 1998, when GemTech was starting to make a bigger splash in the early suppressor market, we typically attended the ADPA / NDIA Small Arms System Conferences. While the crux of my design work was suppressors, I also enjoyed working on odd projects. One was a Modular Weapon System that we showed off at the 1998 conference at FT. Benning. Rail handguard systems were in their infancy, and it occurred to me that having the modularity of a QD barrel would be very handy for mission configuration. I got to work building a prototype upper by hand with no blueprints, which was typically the case with my projects. All built from the mind's eye. It started with a simple existing free-float handguard with steel rails screwed to it and machined out into pic-rails. I worked up a lever / pin system that was similar to the one on the Stoner 63. Since there was no room to get the takedown pin into the barrel extension like the Stoner, I made a sleeve that sat over the chamber area and acted as the locking surface and gas tube support. This is the original  After showing it off and garnering a little interest, the other partners didn't really see the need to branch out from the suppressors, so as an equal partner, but the youngest guy, I was essentially relegated to tossing it into one of my project bins and letting it rest for a few decades. |
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THEN, the Lima Six popped up on my radar last September. I was quite enamored with what they were doing, and the need for a QD barrel made things click, so I started hunting around in my bins. I touched base with Harvey, and he was at least interested in seeing what I might come up with as a standalone project on my own accord. Initially, I knew I needed to modernize my original design. I first thought along the lines of making the system modular and making something that looked more like an open-top handguard like you find on an older M249.  Then I decided that going to a more traditional octagon handguard, with plenty of clearance for the side-mounted gas system, would be more appealing. That said, since the Trunnion Assembly stands alone, different Handguard Sleeves can be designed to fit the Trunnion.  I started with plastic 3D printing for my initial proof of concept, which also helped me refine the system.     Then on to some machined parts for further testing.  
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Through X, I have made a lot of new friends who are also working on projects for the L6, making me remember how much I loved the community, especially all the new guys, who are innovators. Because of all the encouragement, I decided to keep working on the projects and find a good machine shop that does a lot of firearms-related machining to help me bring the project to life. Right now, it is still a personal project, but I am planning on sending some samples to Harvey and a few others to run it through the paces. From there, I will decide where to go with it. I will be getting some more machined parts in soon and will post more pictures as things progress. I look forward to feedback, especially amongst L6 owners Overall, it's pretty satisfying to pull a project I started in the late 1990's and bring it full circle. All this time, it was just waiting for the right host. |
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Originally Posted By OFG_Can_Man: BTW, sorry that the pics are not showing up. Once I figure it out, I will edit so they do. I think its because you are a new user. Other users can 'approve' the images and then they should show up. I can see the pics in your posts. |
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Originally Posted By rbhoover: I am so in! Just waiting on my kit to ship to start building it up! That said, having the ability to have a shorty (12.5") barrel and swapping to a 20" when it suits sounds amazing. I look forward to watching where this goes! Thanks for the encouragement! That is the same train of thought I had. BTW, thanks for letting me know the pics do show up. I appreciate it. |
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One of the great things about the whole L6 project, is Harvey encouraging people to bring accessory ideas to production. There is no doubt an interest in a quick change barrel system. I have no interest in one. I bought an L6 upper because belt feds are very interesting and fun at the range. I will shoot the upper a few times a year, I can’t imagine wanting to do 100 or more round continuous belt dumps, but I know there are people that want to. They will be very interested in your project and I hope you do well. The lower cost and pretty well proven reliability are what sold me on the L6. It goes great with my FM-9D. |
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Originally Posted By MGVINCE: One of the great things about the whole L6 project, is Harvey encouraging people to bring accessory ideas to production. There is no doubt an interest in a quick change barrel system. I have no interest in one. I bought an L6 upper because belt feds are very interesting and fun at the range. I will shoot the upper a few times a year, I can’t imagine wanting to do 100 or more round continuous belt dumps, but I know there are people that want to. They will be very interested in your project and I hope you do well. The lower cost and pretty well proven reliability are what sold me on the L6. It goes great with my FM-9D. Yeah, Harvey is really great about the concept of others creating accessories. I hear you on not necessarily having the need if not putting enough rounds down range. For me, it is more about modularity. I think it will be pretty neat to see all the various configs that come out for the L6. |
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Originally Posted By Gunslinger97: If this can be made to work with tge RRH el Camino handguard system count me in. Several people have asked me about this over on X. I reached out to RRH, since he is only a town over. Unfortunately, he wanted to keep it proprietary to his products, which I completely understand. All that said, we will be coming out with multiple styles of handguard sleeves after the first run and also offering them as options & accessories. It is a very simple changeout, as the Trunnion and QD Collar assemblies don't change. |
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I am 100% in on a QCB. I have a dedicated lower reserved, my current L6 is on a Hydra, so I will buy another upper to do a QCB L6, and I'll take the liberty to dub it the L6A1. Some observations I have on that style of barrel latch, The button sucks The button gets too hot The button needs a lock That is the same style Robison has on the M96 and the MCR/MFR, and I have heard the sea stories on barrels going on a short javelin journey. A secondary lock might help prevent that, especially if it gets knocked during some movement To address the other two issues, a larger button in the shape of an ambi AK mag release or Galil gives you more surface to work with. And adding a delrin bushing to the shaft locking the barrel where it interfaces with the button surface could help. I dicked around with some of this in a friend's foundry and machine shop, but he runs a business and I am real estate developer so they don't get the attention that I wish I could put into firearm projects. |
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Originally Posted By Elcunning: I am 100% in on a QCB. I have a dedicated lower reserved, my current L6 is on a Hydra, so I will buy another upper to do a QCB L6, and I'll take the liberty to dub it the L6A1. Some observations I have on that style of barrel latch, The button sucks The button gets too hot The button needs a lock That is the same style Robison has on the M96 and the MCR/MFR, and I have heard the sea stories on barrels going on a short javelin journey. A secondary lock might help prevent that, especially if it gets knocked during some movement To address the other two issues, a larger button in the shape of an ambi AK mag release or Galil gives you more surface to work with. And adding a delrin bushing to the shaft locking the barrel where it interfaces with the button surface could help. I dicked around with some of this in a friend's foundry and machine shop, but he runs a business and I am real estate developer so they don't get the attention that I wish I could put into firearm projects. Thanks for the encouragement and insights. I had a Robinson and worked with a Stoner quite a bit, and I think that launches are mostly user error. I designed a cam into the pin and QD Collar that should resolve that issue. The handguard sleeve also has protection "wings" to block accidental bumps. On the heat end of things, I am not sure, but hopefully test units will get me enough feedback that I can make needed changes before I go full tilt and start working on production. I tried to design the main components to be as modular as possible, so making changes should be relatively easy. |
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 VID 20260529 145905 Some video of a prototype handguard sleeve being machined. Initially, the prototypes will come with straight MLOK-style sleeves. I do intend to offer make railed sleeves that match the height of the L6. Have to start somewhere though, so MLOK it is. All handguard styles and lengths will be interchangeable with the Trunnion Assembly.  VID 20260529 145830 |
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Welcome and I'm very interested in this project. I think it's very cool all the hands in the Lima Six project. As for the button for barrel retention, I like it. I too have a Robinson Armament M96. The QD barrel system works very well, in my actual use of that style. Its simple and easy to manufacture. I think there may be other options. However, the goal of the original Lima Six project was to bring an affordable belt-fed to the masses. Which it has. I think the add-ons should also follow suit. |
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Originally Posted By aod886: Welcome and I'm very interested in this project. I think it's very cool all the hands in the Lima Six project. As for the button for barrel retention, I like it. I too have a Robinson Armament M96. The QD barrel system works very well, in my actual use of that style. Its simple and easy to manufacture. I think there may be other options. However, the goal of the original Lima Six project was to bring an affordable belt-fed to the masses. Which it has. I think the add-ons should also follow suit. Thanks! I agree. I want to keep things simple, robust, and reasonably priced to go along with the ethos of the L6. |
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Stoner 63/63A Stoner 86 KAC LMG 249/mk46/mk48 All use the same hinged button latch and pin arrangement. I think it’s a fine option, albeit likely with some compromise in accuracy. IMO the very best would be to mimic the QC function of the 240 barrel, but that adds a lot of complexity and is a tougher problem to solve with a gas tube taken into consideration. |
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Originally Posted By JoshNC: Stoner 63/63A Stoner 86 KAC LMG 249/mk46/mk48 All use the same hinged button latch and pin arrangement. I think it’s a fine option, albeit likely with some compromise in accuracy. IMO the very best would be to mimic the QC function of the 240 barrel, but that adds a lot of complexity and is a tougher problem to solve with a gas tube taken into consideration. The problem with using an M240 type system on an AR15 is that the barrel rotates. I prefer the barrel to come straight out, because it will force you to open the bolt before removing the barrel. Since our system is closed bolt, I dont want people to end up with a chambered round and be able to remove the barrel. If its at cookoff temps that could be a bad situation. |
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Originally Posted By AZ_Hi_Desert: Isn't the gas tube on an L6 on the left side of the barrel? I see the gas tube on the QD mock up in the usual 12 o'clock position. Originally Posted By AZ_Hi_Desert: Originally Posted By LimaSix: Watching this with great interest! Isn't the gas tube on an L6 on the left side of the barrel? I see the gas tube on the QD mock up in the usual 12 o'clock position. Correct. On the mockup, I am using an AR upper. Everything is in the correct orientation, just rotated 90 degrees. |
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More parts are coming off the machines today. These are the QD Collars. The system will come with 2ea, so you can have 2 barrels ready to go. These will fit over the barrel and butt up against the barrel extension and be locked down. Will also include some shims to make up for barrel/receiver/collar dimension variations. 
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Having a 3D printer for quick proof-of-concept parts is invaluable. Potential shaping of a future Handguard Sleeve for the barrel system for the Lima Six upper. The initial system will have a straight MLOK handguard with no rail. Once this comes to fruition, it will be an add-on or replacement. Everything else in the system remains the same. Needs MLOK slots, ARCA rail, etc. This helps visualize changes that need to be made.   
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Originally Posted By Falcon09: Very interested for my 18" L6. I also plan to either buy a kit to build a 12.5 or buy a complete 12.5 upper when available. Either way, a quick change barrel would be awesome. The QD Barrel system should be a real boon to those wanting more modularity of an already great upper. I plan to offer different Handguard sleeve styles and lengths once this really gets rolling. |
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The J-6QD barrel project for the L6 upper is gaining steam rapidly. Working on these critical components that will allow for multiple styles and lengths of handguards and other accessories. Also working with a manufacturer to bring back the OG FatBoy belt-fed suppressor... but that is another story in the making.  Machinist checking alignment of the QD Barrel Collar and Trunnion Block before the final run. The QD lever pin holes and gas tube supports need to be right on. 
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Trying to use downtime, while waiting for parts at anodizing, to work on an optional QD handguard sleeve. Seriously considering Nato Rails for top and sides , with ARCA rail on the bottom. The top rail will be level with the L6 top cover rail. May add some MLOK slots on the angled flats for things like sling points. Curious which way people lean for a handguard on their L6 Beltfed. 
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Originally Posted By OFG_Can_Man: Trying to use downtime, while waiting for parts at anodizing, to work on an optional QD handguard sleeve. Seriously considering Nato Rails for top and sides , with ARCA rail on the bottom. The top rail will be level with the L6 top cover rail. May add some MLOK slots on the angled flats for things like sling points. Curious which way people lean for a handguard on their L6 Beltfed. https://pbs.twimg.com/media/HKuEd7ja0AAzd8r?format=jpg&name=large Don’t go with ARCA for a LMG. There are no recoil lugs/stops. Fine for precision rifles, not good on a LMG. Use 1913 on the bottom and top, mlok on the sides for ease of mounting lights, etc. 1913 on the bottom allows the use of the Arisaka Defense Rail Slider. I use this on my HK 23e and it works great. It allows quick positioning of a bipod, while having recoil lugs to prevent unwanted movement from sustained fullauto or FRT fire. |
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Originally Posted By JoshNC: Don’t go with ARCA for a LMG. There are no recoil lugs/stops. Fine for precision rifles, not good on a LMG. Use 1913 on the bottom and top, mlok on the sides for ease of mounting lights, etc. 1913 on the bottom allows the use of the Arisaka Defense Rail Slider. I use this on my HK 23e and it works great. It allows quick positioning of a bipod, while having recoil lugs to prevent unwanted movement from sustained fullauto or FRT fire. This handguard sleeve is still in its infancy. I appreciate any and all feedback. If I went this way, I was planning on adding MLOKs in the ARCA to attach Pic rails and MLOK bipods. At this point it is all open-ended. I plan on offering the full MLOK handguard sleeve, some iteration of this one with the rail, and probably an open-top rail, similar to the M249 rail handguard. The nice thing is, it is all modular. Once you have the Trunnion Assembly and Barrel Collars, any handguard sleeve we end up offering will fit. |
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Originally Posted By OFG_Can_Man: This handguard sleeve is still in its infancy. I appreciate any and all feedback. If I went this way, I was planning on adding MLOKs in the ARCA to attach Pic rails and MLOK bipods. At this point it is all open-ended. I plan on offering the full MLOK handguard sleeve, some iteration of this one with the rail, and probably an open-top rail, similar to the M249 rail handguard. The nice thing is, it is all modular. Once you have the Trunnion Assembly and Barrel Collars, any handguard sleeve we end up offering will fit. Very cool. |
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It has been a long time getting this project to this point. The J-SIX QD barrel System for the Lima-SIX Belt fed upper is almost here. Testers, expect to be hearing from me over the next 2 weeks to get shipping addresses, and I will send some tip and assembly videos in advance so you know what to expect. Time for me to get to work on assemblies. 
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 J-SIX QD Barrel Prototype Fitment for the L6 Beltfed Upper. Things are going smoothly with the initial fitment of the prototypes for the J-SIX QD barrel system that fits the L6 upper. For fitting and prototype purposes, I am working with an AR upper. Prototypes will be shipping to the testers starting next week and the following. |
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 J-SIX MLOK QD Handguard for the Lima-Six Belt Fed Upper. This J-SIX QD Barrel System for the L6 Belt Fed Upper is going to be bad ass! It will be a real game-changer for owners who use it with an FRT. Best part is, once installed, the handguard sleeve can easily be swapped out for different versions that we come out with at a later time. Already working up a rail handguard that matches the L6 topcover rail height and also planning an open-top handguard, reminiscent of the M249. |
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I have started sending out prototype test samples to individuals with whom I locked in a while ago. In the interest of transparency, I am posting an instruction & tip video I sent them to help with installation. In the machined prototypes, I have already found a few areas for improvement. Between these improvements and tester feedback, I feel like we aren't too far off from locking in a production design. This is almost a 30-minute video. Some things won't pertain to the end-product instructions, but I felt it would be good for potential end users to see the process and issues that creep up during prototyping. I do have a cranial vapor-lock at the 14:49 mark and describe the set screw adjustment in the exact opposite of how it is to be done. I make note of that in the video description.  J6 QD Proto installation and tips |
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QD Barrel System for Lima-Six Upper (Page 1 of 2)
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