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Posted: 8/5/2025 10:20:56 PM EDT
| I'm looking for a holding fixture/jig to hold lower receivers when torqueing the castle nut. What are you all using? TIA |
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Thank you sir. Any experiance with any of these? Brownell one looks interesting. |
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I have the NC Star tool. I got it on sale at Primary Arms. Works great for torquing the castle nut and staking. https://www.primaryarms.com/ncstar-vice-block-tool-ar15-ar10 |
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I wouldn't necessarily recommend it vs. the dedicated jigs that Tig posted (especially at full price) but I use a Geissele Reaction Block with four coins. 94 Cent - Geissele & Botach AR Buffer Tube/ Receiver Extension Jig Tip IIRC SOLGW uses the green monster in their shop. No experience with the NCStar or Brownells versions. I'm curious how tight and consistent the tolerances are. |
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| The NC Star tool works great. However, I did replace the clamp screws and grip screw with longer ones with knurled thumb nuts red Lock-Tited so you don’t need to use Allen wrenches. I have used it on several dozen REs with no complaints. Spend more if it makes you feel better but they won’t work any better. |
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Originally Posted By Big-Bore: The NC Star tool works great. However, I did replace the clamp screws and grip screw with longer ones with knurled thumb nuts red Lock-Tited so you don’t need to use Allen wrenches. I have used it on several dozen REs with no complaints. Spend more if it makes you feel better but they won’t work any better. Hmm, you're on to something there. May revist that one. |
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Originally Posted By Big-Bore: The NC Star tool works great. However, I did replace the clamp screws and grip screw with longer ones with knurled thumb nuts red Lock-Tited so you don’t need to use Allen wrenches. I have used it on several dozen REs with no complaints. Spend more if it makes you feel better but they won’t work any better. Found a great deal on the NC Star tool so I went with it. Looks like the newer ones have larger thumb screws than the older models. If not to my liking I'll change them. |
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The NCStar fixtures works okay. Videos online show tightening the bottom tower screw but I don't know why as doing that just tries to pull the tube out of alignment with the lower. I use it like the Brownell's fixture with the floating tower and only secure the top set screws and let the bottom screw stay loose so the tower can align or move as needed. There is another issue with the jig I got but since no one seems to notice it on theirs I guess it is not so much of a problem. |
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Originally Posted By jdtbone: Would you mind sharing the deal? Thank you. @ArizonaAR Try ABCSportz $23.21 |
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Originally Posted By jdtbone: Would you mind sharing the deal? Thank you. @ArizonaAR https://kmtactical.net/product/vism-vice-lower-block-tool-for-ar-15-308-receiver/ |
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Originally Posted By GHPorter: I’m going to be “that guy”. BEV Blocks - which are great tools - are for UPPERs. OP was asking about lower fixtures. BEV blocks can be flipped upside down and used in the magwell. I was the one who suggested that feature when it was being designed.  
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Not just any tool that holds the lower is ideal for installing the carbine-style receiver extension(buffer tube). Yeah, we've been doing it the ideal way for many years because there were no tools available to do it correctly. But, with the introduction of the green, black, and blue tools, there's no reason to do it half-a$$ed any longer. These new tools not only support the buffer tube in position to tighten the castle nut, but are also handy for holding the receiver while installing a lower parts kit. You no longer have to install all the lower parts when the lower is mounted on a wobbly magwell tool. These tools are an inexpensive cure to a longstanding conundrum. YMMV
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Originally Posted By sgtlmj: BEV blocks can be flipped upside down and used in the magwell. I was the one who suggested that feature when it was being designed. https://cdn11.bigcommerce.com/s-9j9zreeu/images/stencil/1280x1280/products/41526/80053/Untitled_1__91404.1420752775.png?c=2?imbypass=on That’s something I hadn’t known before. |
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I made my own, machined from delrin. I had a few 3d printed prototypes. If I can find the stl's maybe I'll upload them somewhere. But I should "refine" them a bit. The machined version is awesome. Couldn't be happier with the functionality. Shown here for threading the rear take-down detent hole, but works just as well for castle nuts. Attached File Attached File Attached File |
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Originally Posted By AFCarbon15: I made my own, machined from delrin. I had a few 3d printed prototypes. If I can find the stl's maybe I'll upload them somewhere. But I should "refine" them a bit. The machined version is awesome. Couldn't be happier with the functionality. Shown here for threading the rear take-down detent hole, but works just as well for castle nuts. https://www.ar15.com/media/mediaFiles/89127/1000035152_jpg-3604396.JPG https://www.ar15.com/media/mediaFiles/89127/1000035150_jpg-3604397.JPG https://www.ar15.com/media/mediaFiles/89127/1000035148_jpg-3604398.JPG Nice work, but it doesn't appear to be able to hold the buffer tube in alignment with the lower when tightening the castle nut. But, maybe I missed something. Also, the jig for tapping the take-down pin hole is overkill. I've done scores of those holes with nothing more than a tap in a handle. I suppose it's nice to have something like that if you have the time and capability of making it, but it's really not necessary. |
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Originally Posted By GHPorter: The receiver extension is indexed by the end plate. It’s trivial to keep it aligned while snugging the castle nut by hand. Once it’s snug, tightening the nut against the receiver isn’t going to move the tube. The RE most definitely can rotate while torquing. Attached File |
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Originally Posted By TGWLDR: The RE most definitely can rotate while torquing. https://www.ar15.com/media/mediaFiles/416992/Screenshot_20250812_082737_Samsung_Inter-3605402.JPG Yup, tolerances, for one thing. |
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Originally Posted By TGWLDR: The RE most definitely can rotate while torquing. https://www.ar15.com/media/mediaFiles/416992/Screenshot_20250812_082737_Samsung_Inter-3605402.JPG I’ve never had that happen. I get the nut really, really tight by hand, then snug it more with the wrench before I even start to secure it for torquing. And I’m neither in a hurry nor doing production work, so I’m paying attention as I do this - but none of mine have ever moved while I was torquing them. Edit to add: wouldn’t the tab shear off if the tube turned that much? |
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Originally Posted By j3_: I'm not sure I ever had one that didn't want to move out of alignment. Yeah, they want to rotate when you get close to the recommended torque. If I'm using a lower receiver block, I like to use the Magpul Armorer's Wrench since it has a closed end and wraps around the receiver extension. I'll then run a stock right up against the wrench which keeps it seated in the castle nut. I'll snug the castle nut down while holding the toe of the stock so it doesn't start moving. (A Magpul MOE stock is good for this since it is strong and easy to get on/off of the receiver extension. When I was doing this for a living, I'd keep a spare MOE stock in the toolbox for just this operation.) The Geissele Reaction Block works great, and I do a similar thing as described above by putting the wrench on the extension, then sliding the receiver extension into the block so that it's resting against the back of the wrench. Prevents the wrench from slipping out of the castle nut and dinging up the crenellations. |
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Originally Posted By GHPorter:Edit to add: wouldn’t the tab shear off if the tube turned that much? No, the tab won't shear off, but the tab will sure damage the groove in the extension when the extension rotates. Some of you guys are going to un-necessary measures to keep the extension from rotating when a simple $25 tool alleviates the problem with hardly any effort. |
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Originally Posted By GHPorter: I’ve never had that happen. I get the nut really, really tight by hand, then snug it more with the wrench before I even start to secure it for torquing. And I’m neither in a hurry nor doing production work, so I’m paying attention as I do this - but none of mine have ever moved while I was torquing them. Edit to add: wouldn’t the tab shear off if the tube turned that much? Are you torquing to the TM spec, or just tightening? There is a difference.
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Originally Posted By GHPorter: TM specs: 40 ft-lb torque. I get the nut really tight before I torque it, and I apply force to the wrench gradually. Originally Posted By GHPorter: Originally Posted By TGWLDR: Are you torquing to the TM spec, or just tightening? There is a difference. TM specs: 40 ft-lb torque. I get the nut really tight before I torque it, and I apply force to the wrench gradually. Copy that. |
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They move. Watch the sotar secret shopper 1st video. I think everyone was off some degree all but one enough I would think would be noticeable. I have tightened hundred or more and can't think of one that it didn't take an effort to keep it lined up. Even torquing them to spec was difficult to fixture before these jigs came along. |
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Originally Posted By George218: Anyone have any experience with the Suppressor Tools option? https://www.suppressortools.com/product/warren-innovative-technologies-llc-4348-50a2672d-6aba-42a9-b911-4c1aff45bc58/ That tool would obviously work, but why spend $125 when the $30 "Blue Tool" works just as well. |
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Buy the vism fixture and be done. I machined this jig years ago before most of the low cost jigs became available. Indexes off the magwell and keeps the buffer tube indexed perfectly with no flex, also helps keeping the castle nut wrench pressed on the castle nut with one hand while torquing.
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Originally Posted By bravo_677: Buy the vism fixture and be done. I machined this jig years ago before most of the low cost jigs became available. Indexes off the magwell and keeps the buffer tube indexed perfectly with no flex, also helps keeping the castle nut wrench pressed on the castle nut with one hand while torquing. https://imgur.com/a/Yo37fto I like your jig. I also like the V7 parts as well. |
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Originally Posted By bravo_677: Buy the vism fixture and be done. I machined this jig years ago before most of the low cost jigs became available. Indexes off the magwell and keeps the buffer tube indexed perfectly with no flex, also helps keeping the castle nut wrench pressed on the castle nut with one hand while torquing. https://imgur.com/a/Yo37fto Your fixture is very nice. Does it require two vises to hold the separate fixtures for the magwell and the receiver extension? |
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Originally Posted By hdcharlie: Your fixture is very nice. Does it require two vises to hold the separate fixtures for the magwell and the receiver extension? No it does not, just drop in, clamp the buffer tube, and torque away. The base plate can be set up in a vise or bolted to a table |
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Originally Posted By bravo_677:No it does not, just drop in, clamp the buffer tube, and torque away. The base plate can be set up in a vise or bolted to a table Ok, I see now. I didn't realize the two vertical fixtures were mounted to the base plate. Should be easier to use than the VISM tool, but would be more expensive to manufacture. Wouldn't want to sell one would ya? 
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Originally Posted By hdcharlie: Ok, I see now. I didn't realize the two vertical fixtures were mounted to the base plate. Should be easier to use than the VISM tool, but would be more expensive to manufacture. Wouldn't want to sell one would ya? You could buy 20 vism fixtures for the price of this one  I went through several design changes and materials to get to this point.
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Originally Posted By bravo_677:You could buy 20 vism fixtures for the price of this one I went through several design changes and materials to get to this point.That's pretty much what I figured. It looks really nice, but the VISM I have will do. 
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