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SRU Bullpup Conversion. EDIT: Got one! Build starting. (Page 1 of 2)
Posted: 8/21/2024 10:38:41 AM EDT
[Last Edit: Thor][Edited]
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I’ll probably be ordering one of these to play with. Much cheaper than the other alternatives…though that didn’t stop me from buying the others, lol. Reminds me of the Scy conversion kit, only the scy looks like the prototype of this. Curious to see how well built it is. The mag release hardware does look a little janky to me…interested to see how it’s built. Two neat things: It is compatible with milspec uppers if you use the Dead Foot Arms buffer system and works with the CMMG .22 conversion kit. This does increase the LOP but it can’t possible be any worse than the Hellion. It has a paddle mag release behind the mag that should feel more familiar to us bullpup users. Edit: I’ve shot an email over to inquire on fat handguard fitment. If it’s a yes, I’m ordering. A milspec upper with DFA buffer kit, an Aero Enhanced 10.7 rail , 6” 300blk barrel, and tucked supressor sounds like PDW heaven. Edit for new info: - LOP is 15.3” - 9.5” handguard fits flush to the end of the chassis. https://www.sru-precision.com/ https://www.sru-precision.com/sarb-15 Attached File Attached File |
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Do you have use Jakl parts? It can't be used with all mil spec parts (buffer etc)? Not great imo Had an 10.5 SBR would convert with this, but if I have buy a bunch of stuff plus the $350 kit not as attractive. |
"According to Argonne National Laboratory, it takes 100 pounds of battery in an EV to go a distance achieved by only one pound of gasoline in an ICE vehicle"
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Definitely can not be used. The LOP introduced by a milspec buffer assembly would make it unusable anyway. Attached File |
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Originally Posted By Thor: Definitely can not be used. The LOP introduced by a milspec buffer assembly would make it unusable anyway. https://www.ar15.com/media/mediaFiles/66797/IMG_5055_jpeg-3300619.JPG Good to know. |
"According to Argonne National Laboratory, it takes 100 pounds of battery in an EV to go a distance achieved by only one pound of gasoline in an ICE vehicle"
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Originally Posted By SpyHawk: You should totally use a 10.5 SBR. You just have to use either an ARIC, DFA, or Evolution Weapons Systems bolt carrier setups. Hardly a lot of parts. Will research. Not familiar with those. |
"According to Argonne National Laboratory, it takes 100 pounds of battery in an EV to go a distance achieved by only one pound of gasoline in an ICE vehicle"
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I wish they had a better writeup or video on assembly, exactly what is needed (Jakl or otherwise) to complete, and what options there are. It's all very vague. |
"According to Argonne National Laboratory, it takes 100 pounds of battery in an EV to go a distance achieved by only one pound of gasoline in an ICE vehicle"
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Originally Posted By _DR: I wish they had a better writeup or video on assembly, exactly what is needed (Jakl or otherwise) to complete, and what options there are. It's all very vague. The second link has tons of info and charts the more you scroll down. No instructions though. It appears to only require a lower and bufferless upper. For a milspec upper it requires one of the DFA buffer kids or something the the LAW bufferless bcg. Comes with all hardware to use on mlok or pic rails. There is a chart with handguard limits in the second link as well. Attached File |
| With the use of a mil spec upper you could use a dedicated 22 LR barrel and the barrel collar on the CMMG bolt to have a bullpup 22 LR. Plenty of 22 LR CMMG pattern mags to choose from, even BDM drum. The 5.56/223 barrel and chamber insert on CMMG conversion bolt work but not optimal twist for 22 LR. |
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Also found this. Looks to be the 9” FM15 upper. Those have an 8” handguard. Attached File |
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Good pic on the gram. https://www.instagram.com/p/C_F-I2dT49g/?igsh=NHUzczZvMXR5NGJu |
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Originally Posted By SpyHawk: Good pic on the gram. https://www.instagram.com/p/C_F-I2dT49g/?igsh=NHUzczZvMXR5NGJu [instagram]C_F-I2dT49g[/instagram] Nevermind. |
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Originally Posted By backbencher: [instagram]C_F-I2dT49g[/instagram] Nevermind. Attached File |
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Originally Posted By Stonia: Originally Posted By backbencher: [instagram]C_F-I2dT49g[/instagram] Nevermind. https://www.ar15.com/media/mediaFiles/203509/1000009649_jpg-3305258.JPG Ok... my upper's bolt system is longer than that system can host. So there remain some important pieces of this puzzle still missing. |
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Originally Posted By FrozenIceman: I can't imagine that trigger feeling good. It actuates the Stock Trigger so assuming it is a good trigger to begin with. Then another 4 or 5 pivot points, each with their own tolerance. It’s very similar to the TRIAD kit. That trigger is damn good for a bullpup, and insanely good for a conversion. |
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Originally Posted By Stonia: Does it have 2 safeties to manage then? Looks like the normal AR safety is exposed for use, but then maybe also a trigger saftey on the conversion parts? I saw it mentioned they left it accessible incase you had Binary or F/A. A3 did the same thing, but there’s a cover plate you can install if you choose not to use the receiver safety. |
| I just popped for a LAW Tactical ARIC on the EE... This bullpup kit is intriguing. Anyone shot one yet? |
Scepticism is an exercise, not a life; it is a discipline fit to purify the mind of prejudice and render it all the more apt, when the time comes, to believe and to act wisely. -- George Santayana
Never mistake a clear view for a short distance.
Never mistake a clear view for a short distance.
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Ended up ordering a conversion kit, used an obvious coupon code so final price was $364 shipped Fedex Priority from Taiwan... Not kidding around, ordered last Thursday got it today (Tuesday following). The chassis is a bit on the flexy side when assembling, but once everything is together there is no play or flex. Trigger is pretty darned good; I have a Geissele SSA in the SBR lower I'm using. Clearing the charging handle with my face will take a little getting used to. I didn't want to spring for a full FM Products or Brownells side charging upper... And you'll need a riser or tall mount for your optic. I'm going to try a 6.5 Grendel bolt in the ARIC; I'm probably in for a lot of pain and frustration, but maybe I'll get lucky...  12.5" Grendel barrel, 11" handguard: 
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Scepticism is an exercise, not a life; it is a discipline fit to purify the mind of prejudice and render it all the more apt, when the time comes, to believe and to act wisely. -- George Santayana
Never mistake a clear view for a short distance.
Never mistake a clear view for a short distance.
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Originally Posted By vmpglenn: Ended up ordering a conversion kit, used an obvious coupon code so final price was $364 shipped Fedex Priority from Taiwan... Not kidding around, ordered last Thursday got it today (Tuesday following). The chassis is a bit on the flexy side when assembling, but once everything is together there is no play or flex. Trigger is pretty darned good; I have a Geissele SSA in the SBR lower I'm using. Clearing the charging handle with my face will take a little getting used to. I didn't want to spring for a full FM Products or Brownells side charging upper... And you'll need a riser or tall mount for your optic. I'm going to try a 6.5 Grendel bolt in the ARIC; I'm probably in for a lot of pain and frustration, but maybe I'll get lucky... 12.5" Grendel barrel, 11" handguard: https://personal.visualitymedia.com/personal/65g_bullconv.jpg Very interested in this project! Can you please list what all you had to buy for this? At present, all my guns are conventional DI with buffers, which I don't think works for this. |
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Originally Posted By lazyengineer: Very interested in this project! Can you please list what all you had to buy for this? At present, all my guns are conventional DI with buffers, which I don't think works for this. Aside from the bullpup kit, I just bought a Law Tactical ARIC off the EE. My SARB-15 required some modification to work with the ARIC. I had to hog out the ID of the stubby receiver extension by about .01" so the ARIC would slide in and out freely. SRU Precision wanted me to tap my ARIC in as sort of a force-fit, but according to Law Tactical that's a no-no. I'm also trying to see if I can modify the mag release lever so it depresses the mag catch all the way. Right now it goes about halfway, which is not enough to release PMAGs. I also ended up switching to a 5.56 barrel and using the ARIC in its factory configuration. Here's how it sits right now: 
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Scepticism is an exercise, not a life; it is a discipline fit to purify the mind of prejudice and render it all the more apt, when the time comes, to believe and to act wisely. -- George Santayana
Never mistake a clear view for a short distance.
Never mistake a clear view for a short distance.
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Originally Posted By vmpglenn: Aside from the bullpup kit, I just bought a Law Tactical ARIC off the EE. My SARB-15 required some modification to work with the ARIC. I had to hog out the ID of the stubby receiver extension by about .01" so the ARIC would slide in and out freely. SRU Precision wanted me to tap my ARIC in as sort of a force-fit, but according to Law Tactical that's a no-no. I'm also trying to see if I can modify the mag release lever so it depresses the mag catch all the way. Right now it goes about halfway, which is not enough to release PMAGs. I also ended up switching to a 5.56 barrel and using the ARIC in its factory configuration. Here's how it sits right now: https://personal.visualitymedia.com/personal/556_bullconv.jpg Have you tried simply backing out the mag catch a few turn to make the button stick out further? I’m not sure how the lever works, but that should either decrease the required travel, or “preload” the button if there’s flex in the mechanism. I had to play with the TRIAD mag release a bit too before I found the sweet spot. |
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Originally Posted By vmpglenn: Aside from the bullpup kit, I just bought a Law Tactical ARIC off the EE. My SARB-15 required some modification to work with the ARIC. I had to hog out the ID of the stubby receiver extension by about .01" so the ARIC would slide in and out freely. SRU Precision wanted me to tap my ARIC in as sort of a force-fit, but according to Law Tactical that's a no-no. I'm also trying to see if I can modify the mag release lever so it depresses the mag catch all the way. Right now it goes about halfway, which is not enough to release PMAGs. I also ended up switching to a 5.56 barrel and using the ARIC in its factory configuration. Here's how it sits right now: https://personal.visualitymedia.com/personal/556_bullconv.jpg Originally Posted By vmpglenn: Originally Posted By lazyengineer: Very interested in this project! Can you please list what all you had to buy for this? At present, all my guns are conventional DI with buffers, which I don't think works for this. Aside from the bullpup kit, I just bought a Law Tactical ARIC off the EE. My SARB-15 required some modification to work with the ARIC. I had to hog out the ID of the stubby receiver extension by about .01" so the ARIC would slide in and out freely. SRU Precision wanted me to tap my ARIC in as sort of a force-fit, but according to Law Tactical that's a no-no. I'm also trying to see if I can modify the mag release lever so it depresses the mag catch all the way. Right now it goes about halfway, which is not enough to release PMAGs. I also ended up switching to a 5.56 barrel and using the ARIC in its factory configuration. Here's how it sits right now: https://personal.visualitymedia.com/personal/556_bullconv.jpg Thank you. So the secret to getting this to work, is getting an ARIC bolt. Which simply is this, which eliminates the BCG and buffer travel back into where a buffer tube would normally be needed. I'm not familiar with the ARIC, but from what little I can see, they appear to have some serious reliability issues. Or at least, there are numerous complaints. How is yours working out? Also, apparently the retail price of such can be on the order of $400. Which is a substantial project cost adder, though used ones seem to be more approachable. So much so, that it kind of supports the concern that maybe these aren't working out to be so reliable? 
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Originally Posted By lazyengineer: Thank you. So the secret to getting this to work, is getting an ARIC bolt. Which simply is this, which eliminates the BCG and buffer travel back into where a buffer tube would normally be needed. I'm not familiar with the ARIC, but from what little I can see, they appear to have some serious reliability issues. Or at least, there are numerous complaints. How is yours working out? Also, apparently the retail price of such can be on the order of $400. Which is a substantial project cost adder, though used ones seem to be more approachable. So much so, that it kind of supports the concern that maybe these aren't working out to be so reliable? https://www.shootingillustrated.com/media/v1qh5iip/law-tactical-aric.jpg Get the Dead Foot Arms MCS 2.5” buffer system. https://www.opticsplanet.com/dead-foot-arms-modified-cycle-system-rifle-caliber-ar-pistol-kit-w-bolt-carrier.html Not only is it more adjustable and more reliable, It also uses a cut down M-16 profile BCG. Super safety’s and FRT triggers are compatible, if you’re into that kinda thing.  |
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Thank you @Thor, spinning the mag catch out three turns did the trick; mags eject with no issue now. SRU Precision's customer service has been good - they answer emails promptly. I ended up swapping the optic for one with a 1.7" mount; height is now perfect for a comfortable heads-up position with the rifle shouldered. 
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Scepticism is an exercise, not a life; it is a discipline fit to purify the mind of prejudice and render it all the more apt, when the time comes, to believe and to act wisely. -- George Santayana
Never mistake a clear view for a short distance.
Never mistake a clear view for a short distance.
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Originally Posted By Thor: Also found this. Looks to be the 9” FM15 upper. Those have an 8” handguard. https://www.ar15.com/media/mediaFiles/66797/IMG_5133_jpeg-3303086.JPG Wish the match up of this was a little cleaner or more flush. I've got an fm15 in 11.5 I'd love to convert at these prices. |
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So far, the ARIC works just fine with 5.56 pressure ammo, does not like .223 at all. That's in the ARIC manual so no real surprise. |
Scepticism is an exercise, not a life; it is a discipline fit to purify the mind of prejudice and render it all the more apt, when the time comes, to believe and to act wisely. -- George Santayana
Never mistake a clear view for a short distance.
Never mistake a clear view for a short distance.
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Originally Posted By vmpglenn: So far, the ARIC works just fine with 5.56 pressure ammo, does not like .223 at all. That's in the ARIC manual so no real surprise. Yea that's a hard no. All my guns run a wide wide spectrum of 5.56 ammo pressure and spec just fine. and My Grendel ammo can be same. If I'm going to spend this much total-cost for a Grendel bullpup, it's going to need to be more reliable for me then that, so I'm not sure ARIC is the way for me here. The other bolt option maybe though... |
| https://www.ar15.com/forums/ar-15/Revising-my-old-guy-s-AR-15-Bullpup-project/4-788042/ |
I sell firearms produced by the finest child labor in the world, be it Filipino, Muslim, Mormon, Arizonan, or Texan.
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Updated with a Rovyvon LAM, AT3 slick sided upper, Kung Fu grip, Vortex 3x prism. Fun little package. 
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Scepticism is an exercise, not a life; it is a discipline fit to purify the mind of prejudice and render it all the more apt, when the time comes, to believe and to act wisely. -- George Santayana
Never mistake a clear view for a short distance.
Never mistake a clear view for a short distance.
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Originally Posted By vmpglenn: Updated with a Rovyvon LAM, AT3 slick sided upper, Kung Fu grip, Vortex 3x prism. Fun little package. https://personal.visualitymedia.com/personal/556_bullpupconv_lam.jpg You've got plenty of room to put the LAM on top so that you can have a two-distance zero (50/200 or whatever works). Plus it won't get blocked by barricade shooting. |
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Originally Posted By SpyHawk: You've got plenty of room to put the LAM on top so that you can have a two-distance zero (50/200 or whatever works). Plus it won't get blocked by barricade shooting. Yeah, you're right. 
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Scepticism is an exercise, not a life; it is a discipline fit to purify the mind of prejudice and render it all the more apt, when the time comes, to believe and to act wisely. -- George Santayana
Never mistake a clear view for a short distance.
Never mistake a clear view for a short distance.
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Damn. That’s fast! Attached File I won’t be getting mine together any time soon. I just need to to take some measurements and I’ll be looking into modification options before I decide what route I’m going to go. |
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So I got it in. I haven't got all the parts yet as I'm still deciding on how to configure this. I got a few handguards to test. I wanted something with a more solid lockup since I'll be mounting an optic on the handguard. Found the perfect one for it. Daniel Defense MFR XL. This is just outside SRU's specs for compatibility, but it required minimal modification to the chassis to make work. Just had to take a dremel and remove some material from the inside to make room for the bolting area on the handguard. Why is this the perfect rail for me? Cause now I can tuck a suppressor. If I want to run a 5" 300blk barrel and a can, I can do so in a 25" OAL package. Attached File Where to dremel: Attached File |
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If you want to run something more practical, like a 8"-9" 300blk, you can still use the extended handguard to tuck the rest of the suppressor. As I said, the handguard is a bit to large according to the compatibility chart, but with the MFR XL, the SRU handguard slides on perfectly. But you have to have it lined up perfect to get it on. It was easier to take the top off and slide the main part on first, then reattach the top. The handguard almost tension lock against their taper. There was a little bit of upward play on the handguard when mounted to the chassis. Pairing the extended handguard with the MFR XL makes the entire chassis feel rock solid. Attached File Attached File |
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The MFR XL is 10", too long for the 9.5" maximum length in the compatibility chart (though I think it's more like 9.75"). Because of this, you cannot slide the SRU handguard all the way back to its attachment points. I haven't done it yet, but i will have to shave .2-.21" off the the lower rear top section of the SRU handguard so I can slide it all the way back. All I have to do is cut it straight down and remove the angle. Aesthetically, this will also nearly close the gap between the top of the two rails more a better look, in my opinion. Attached File Attached File |
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Still waiting on the barrel and grips, so did some Cerakote cause I can’t leave anything alone. I wasn’t feeling very creative so nothing flashy this time, lol. Also have the Super Safety all fitted and running smooth with another upper. It’ll look better with the button back there instead of a lever anyway. This thing is going to be so much fun. Attached File Attached File Attached File |
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6” barrel and short can, 8” barrel and long can. Attached File Attached File |
Joined:
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CA, USA
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So I've had this kit for a while now and have spent alot of time tinkering with it, instead of starting a new thread I figured I'd post some of my insight here. Due to the machining tolerances between different lower manufacturers, not all lowers fit equally. One Spikes tactical lower sat pointing upward, one later production BCM lower was severely canted to the left, and one earlier production BCM that I had on a lightweight bulid sat level enough that thats what I'll most likely end up using. The Spikes lower needed too much pressure on the front takedown pin it visibly flexed the shell too much for my comfort. I'd like to have tested other brand lowers but most of what I have on hand are billet or integrated trigger guard. The trigger mechanism is surprisingly well made and a few shims on the stock trigger can take the left to right slop out-of it. The magazine catch leaves a bit to be desired but it works well enough once the button is adjusted to contain the lever pad. There are two points of contact that keep the receiver in the shell and that's the grip screw area and the buffer tube. With the full weight of a 16" barreled upper there is alot of play and rocking motion even with the front takedown pin adjusted. I might machine a block of aluminum that attaches to the handguard directly once I decide what handguard I'm going to use. The handguard is a stamped piece of thin steel but is very heavy. There are some adhesive pads that go behind the mlok slots, this adds thickness otherwise some rail sections will bottom out on the nut, not the handguard, before being fully tightened and will be loose. A fully assembled lower will fit into the kit in case anyone wants to check their lower fit without having do do any dissasembly other than the grip.  It's going to be a long time before I finish this project, most likely will be a range gun only |
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Originally Posted By Nickel_Plated: Combine this with one of those AR-57 uppers and it might make a neat "P90 we have at home" https://ar-57center.com/wp-content/uploads/2023/01/main-qimg-456c568124e20e4ea0353d9774934822.png I had one a long time ago. They’re boat anchors. |
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Added the A3 Tactical rail riser. Super safety is a no-go. Not compatible with the DFA buffer kit. 6” barrel won’t cycle subs. Will will eject but won’t lock back. Gas port is oversized. Need some weaker springs for the buffer to get it to run but no luck finding anything as of yet, so I’m sticking with the 8” for now. Also got the Geissele SD-E flat trigger to work, despite it saying the kit only works with curved triggers. The 2 stage trigger still feels really nice in the chassis.  
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SRU Bullpup Conversion. EDIT: Got one! Build starting. (Page 1 of 2)
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