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AR mechanics - help please

bisleybisley Senior MemberPosts: 10,798 Senior Member
My grandson's AR-15 has a factory installed thin profile ~12" free float hand guard that attaches to a threaded Yankee Hill style barrel nut, and is secured by a jam nut (ring).

The problem is that the hand guard can be rotated about an 1/8" by gripping the hand guard and twisting on the upper receiver. It appears that the barrel nut 'ring' may be moving, so I am afraid that they may have failed to torque the barrel properly at the factory. The ring part of the barrel nut has a jam nut/ring that spins freely around it that is used to secure the hand guard. The hand guard has one recessed Allen head screw at the bottom, that is tightened to lock the position of the hand guard. The barrel nut, as near as I can tell, is the same used on Yankee Hill hand guard systems, but there is no identification that I can find.

I want to remove the hand guard and check the torque on the barrel nut. If it is OK, I need to figure out why the hand guard is rotating, and fix it, or replace it, if necessary. But, when I loosen the Allen (hex) screw and back the jam nut off all the way, the hand guard does not release. Either the jam nut is still holding it when backed off all the way to the receiver, or the hand guard just won't turn loose from the tube it slides onto, before engaging the jam nut threads. Since I didn't put it together, I can't tell which it is. There are no other screws on the hand guard to hold it on - just the jam nut (and the one recessed hex screw for indexing). I have used penetrating oil and light blows on the hand guard, with a hard plastic mallet, to try to break it loose, with no results. I can't twist the hand guard because it hits the gas block, but it will turn about an 1/8" till it hangs up on the gas block/tube.

Any ideas on how to get the hand guard off? I don't have the ability to take a picture of it, at the moment, so I hope my description is clear.
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Replies

  • JayJay Senior Member Posts: 3,858 Senior Member
    Kinda hard to tell without knowing which handguard it is or having a pic. Usually, those free float tubes thread onto the barrel nut, so the handguard would have to be threaded off. So you'd have to loosen the set screw and unthread it from the front, which would require the removal of the gas block in your case if it's hitting that and not letting it rotate. What kind of gas block? Regular front sight post or some kind of railed or low profile gas block? Either way, not hard to get off. On the front sight post/gas block, the pins are directional. You can usually tell by looking at them that one side is bigger diameter than the other. Sometimes takes some good hits to a punch to get them to come loose.

    If you get it apart and check the barrel nut and if it needs to be torqued, minimum 35 ft lbs, then tighten until the next gas tube hole lines up if necessary.
  • JayJay Senior Member Posts: 3,858 Senior Member
    In other words, and again without knowing the exact setup your dealing with, the inside of the handguard tube will have female threads and the outside of the barrel nut is male threads. The tube is threaded onto the barrel nut, then the ring and set screw lock it in place so it shouldn't rotate. If the whole thing is rotating when you turn it, it sounds like the barrel nut is loose and is able to move back and forth as much as the gas tube going through it will allow. With that set ring and set screw loose, the handguard tube would be threaded off of the barrel nut to be removed.
  • knitepoetknitepoet Senior Member Posts: 21,076 Senior Member
    As many different attachments as there are for FF tubes, there's no way I can tell you which type yours has.

    IF, you know, or can find out, who made it, you might either be able to find something online about removing it, or contact the manufacturer and get some guidance. Sorry, but that's all I've got
    Seven Habits of Highly Effective Pirates, Rule #37: There is no “overkill”. There is only “open fire” and “I need to reload”.


  • LerchessLerchess Senior Member Posts: 550 Senior Member
    Try some heat on there and exert a lot of pressure.

    Chances are they have red locktite on there.
  • bisleybisley Senior Member Posts: 10,798 Senior Member
    I've looked at all the videos. I'm pretty sure I know how it is supposed to come off - I just can't get it to come off. I've been afraid to get too rough with it because I can't tell if the jam nut threads are completely disengaged from the hand guard. It has a low profile gas block underneath the hand guard, that fits in a channel - so the hand guard, itself cannot be rotated - it has to be unscrewed entirely from the jam nut. The video TrueTone911 posted above is pretty close to what it looks like, but unlike in the video, the hand guard cannot be spun off, because the gas tube fits into a raised channel of the hand guard. It is a small diameter hand guard with a raised channel for the picatinny rail. I think that the only way it can work is for the barrel nut to have a smooth sleeve on the muzzle side of it that fits the hand guard with fairly close tolerance, and is secured by the jam nut. The single hex nut on the bottom of the hand guard is for 'rotational' indexing only, while tightening the jam nut, to secure it.

    I'm thinking that the hand guard has bonded tightly to the sleeve, and that it will take a good bit of force to 'unseize' it. At this point, I'm willing to risk ruining the hand guard to get it off, because I want to check the torque on the barrel nut before I let the grandson shoot it again.
  • BigDanSBigDanS Senior Member Posts: 6,973 Senior Member
    bisley wrote: »
    I've looked at all the videos. I'm pretty sure I know how it is supposed to come off - I just can't get it to come off. I've been afraid to get too rough with it because I can't tell if the jam nut threads are completely disengaged from the hand guard. It has a low profile gas block underneath the hand guard, that fits in a channel - so the hand guard, itself cannot be rotated - it has to be unscrewed entirely from the jam nut. The video TrueTone911 posted above is pretty close to what it looks like, but unlike in the video, the hand guard cannot be spun off, because the gas tube fits into a raised channel of the hand guard. It is a small diameter hand guard with a raised channel for the picatinny rail. I think that the only way it can work is for the barrel nut to have a smooth sleeve on the muzzle side of it that fits the hand guard with fairly close tolerance, and is secured by the jam nut. The single hex nut on the bottom of the hand guard is for 'rotational' indexing only, while tightening the jam nut, to secure it.

    I'm thinking that the hand guard has bonded tightly to the sleeve, and that it will take a good bit of force to 'unseize' it. At this point, I'm willing to risk ruining the hand guard to get it off, because I want to check the torque on the barrel nut before I let the grandson shoot it again.

    Go to a gunsmith...

    That is all.

    D
    "A patriot is mocked, scorned and hated; yet when his cause succeeds, all men will join him, for then it costs nothing to be a patriot." Mark Twain
    Alcohol, Tobacco, Firearms and Explosives.... now who's bringing the hot wings? :jester:
  • bisleybisley Senior Member Posts: 10,798 Senior Member
    What is the point of buying a 'lego' rifle if you can't replace the parts on it, yourself? I'm asking for advice from someone who may have already solved this 'plumbing' problem. I'll solve it myself, if necessary - I'm just trying to reduce the pain of this learning experience, as much as possible. :jester:


    The barrel nut below is similar to what I have, in that it has the jam nut that threads onto the hand guard and is tightened to secure the hand guard, but different in that I think there must be no threading on the muzzle end. The one shown here is for a screw-on full diameter quad rail, whereas my rail is a small diameter with a channel for the gas tube/block which eliminates the possibility of the hand guard being spun on. It is simply secured by the jam nut and a tight fit on the sleeve that it slides over, plus one hex screw at the bottom that clamps the handguard to the sleeve to hold it in place while the jam nut is tightened.
    AM-66-FF-NR_1-450x300.jpg

    The hand guard below installs similar to mine, except mine is a narrow diameter that doesn't spin on over the gas tube/block.

    ar-15-quad-rail-handguard-165-inch-free-float-black-540.jpg
  • bisleybisley Senior Member Posts: 10,798 Senior Member
    Jay wrote: »
    .....With that set ring and set screw loose, the handguard tube would be threaded off of the barrel nut to be removed.

    I would agree...except that it is impossible to spin off the handguard without removing the gas block and tube, which is under the hand guard and fits in a channel that allows for the small diameter hand guard. That leaves me to believe that the jam nut (lock ring) is all that secures the hand guard, except for a tight fit on the sleeve that the hand guard slides over.
  • Diver43Diver43 Senior Member Posts: 10,903 Senior Member
    I have a hand guard very similar to what you are describing. It is not actually free floated as it does not thread onto the barrel nut. It goes into the sleeve just like a regular hand guard except it is very tight. The tube is actually two pieces that have very well hidden hex screws that hold the two pieces together and on the nut very tightly, I believe there are three of them. If it is like that the only way to remove it is to take out the hex screws and use a hand guard removal tool as the ring is so tight you can not move it by hand.
    I already have an extra nut as if/when I remove this hand guard I am sure that it may be deformed.
    Logistics cannot win a war, but its absence or inadequacy can cause defeat. FM100-5
  • JayJay Senior Member Posts: 3,858 Senior Member
    bisley wrote: »
    I would agree...except that it is impossible to spin off the handguard without removing the gas block and tube, which is under the hand guard and fits in a channel that allows for the small diameter hand guard. That leaves me to believe that the jam nut (lock ring) is all that secures the hand guard, except for a tight fit on the sleeve that the hand guard slides over.

    OK. I thought the gas block was in front of the handguard and was preventing it from coming off that way. Now that you describe it more, I kinda get what you're saying. I haven't worked on one like that, so I got nothing to offer now... Sorry.
  • bisleybisley Senior Member Posts: 10,798 Senior Member
    Maybe this will clear it up.


    9e49927a-05d6-4be2-9481-741754ba8318.jpg00557bcc-8b25-47f7-90aa-f1d7f2ddfd7b.jpg

    Notice the gas block against the hand guard, indicating (to me) that the barrel nut must have slipped.
  • bisleybisley Senior Member Posts: 10,798 Senior Member
    I bought it at a gun show from a reputable dealer, as a complete upper. I thought it was a Palmetto, at the time, and decided to risk it because it had a 1:8 barrel. It was shooting fine, but now I think the barrel nut has slipped, and I won't be satisfied until I take it apart and check it, and figure out a better way to index the hand guard so that it doesn't slip. I like this hand guard, but I'll replace it if it won't stay put, or if I wreck it trying to get it off.
  • mythaeusmythaeus Senior Member Posts: 831 Senior Member
    I used to have a similar YHM with the same barrel nut jam nut setup, but that's long gone so I don't remember enough to figure out the problem. Maybe give YHM a call and see if they can help? http://yhm.net/support/ (1-877-892-6533 Mon - Fri 7:30am to 4pm EST)
    "In a controversy, the instant we feel anger we have already ceased striving for the truth and have begun striving for ourselves." - Siddhartha Gautama
  • Farm Boy DeuceFarm Boy Deuce Senior Member Posts: 6,083 Senior Member
    The hand guard is moving but can you see the barrel nut move? In your second picture it looks like maybe you can see the barrel from the receiver side.

    If you can see it make an indexing mark with a sharpie or paint pen and see if the barrel nut is actually moving. Go from there.
    I am afraid we forget sometime that the basic and simple things brings us the most pleasure.
    Dad 5-31-13
  • bisleybisley Senior Member Posts: 10,798 Senior Member
    The hand guard is moving but can you see the barrel nut move? In your second picture it looks like maybe you can see the barrel from the receiver side.

    If you can see it make an indexing mark with a sharpie or paint pen and see if the barrel nut is actually moving. Go from there.

    The barrel nut is definitely moving. If it weren't for the gas tube, I could unscrew the whole thing, barrel nut and all.
  • MichakavMichakav Senior Member Posts: 2,726 Senior Member
    Is the gas block set-screw or pinned?
  • DoctorWhoDoctorWho Senior Member Posts: 9,496 Senior Member
    IIRC, using the barrel nut tool, the one that sort of looks like a bent clothes hanger, remove the barrel assembly and slide it off, AFAIR, there was often play in cheap dinky dow handguard assemblies, the better ones do not, also AFAIR, I do not recall ever seeing a barrel nut loose, and we used to build lots of kit AR-15s...
    "There is some evil in all of us, Doctor, even you, the Valeyard is an amalgamation of the darker sides of your nature, somewhere between your twelfth and final incarnation, and I may say, you do not improve with age. Founding member of the G&A forum since 1996
  • Farm Boy DeuceFarm Boy Deuce Senior Member Posts: 6,083 Senior Member
    I hate to say it but I think you are going to have to get the gas block off the barrel.

    With only one set screw and the lock nut there is just no way I can see the FFT being an interference fit on the barrel nut. The FFT HAS to be threaded onto the barrel nut. At least in my limited experience.

    Good luck.
    I am afraid we forget sometime that the basic and simple things brings us the most pleasure.
    Dad 5-31-13
  • bisleybisley Senior Member Posts: 10,798 Senior Member
    Yep. I will have to wreck the hand guard to get at it. If the hand guard screws on, I don't know how they could have done it. I think that what I've been calling a jamb nut is actually a locking ring that holds the whole thing together on an un-threaded sleeve on the barrel nut. Anyway, I can't back the locking ring off enough to release it before it hangs up on the receiver, and I can't budge the hand guard to get any slack on the locking ring.

    I reckon I'll cut through the bottom of the hand guard to get at the gas block screws, and remove it, if I can tap it loose somehow, under the hand guard. If I can't, I'll just have to ruin the hand guard to get at it.

    Such are the hazards of buying gun show bargains. I wish I would have ordered from Palmetto, but I didn't know much about them at the time - the upper I ordered for myself is very good for a budget rifle. I may give it to my grandson, and tinker with this one for my 'cheap' rifle.
  • Diver43Diver43 Senior Member Posts: 10,903 Senior Member
    Bisley, what does the set screw do? Are there any others? That looks a whole lot like the one I have
    Logistics cannot win a war, but its absence or inadequacy can cause defeat. FM100-5
  • bisleybisley Senior Member Posts: 10,798 Senior Member
    The set screw is supposed to keep the handguard from rotating. It should have several - it has one, only, on the bottom, with no hole or indent to fit into. It just clamps the hand guard to the barrel nut sleeve, and poorly. It is either a very poor design, or it was installed incorrectly. It is basically a crapped up version of the Yankee Hill system, as near as I can tell.
  • breamfisherbreamfisher Senior Member Posts: 13,493 Senior Member
    I wonder if the handguard is glued to the barrel nut? Some folks use red loctite to do that, which I believe can be broken with judicious heat and a little tapping at the seam. Might want to check on that.

    Another option is they used epoxy, which I believe is used on carbon fiber handguards.
    Overkill is underrated.
  • bisleybisley Senior Member Posts: 10,798 Senior Member
    It would be worth a try, before I break out the saw, and it will give me an excuse to buy one of those little propane torches.

    EDIT: Hmmm. This begs the queston: If you heat up red loctite to 600 degrees, or whatever it takes to break the bond, does it re-seal when it cools off?
  • Diver43Diver43 Senior Member Posts: 10,903 Senior Member
    Breamfisher may be on to something. I know mine fit very tightly and are going to be a beast to take out, but there is no set screw or glue or whatever.
    Mine being two pieces is pulled tight on the nut as the three screws are tightened. Do not know the make as it was gifted to me without a box
    Logistics cannot win a war, but its absence or inadequacy can cause defeat. FM100-5
  • Diver43Diver43 Senior Member Posts: 10,903 Senior Member
    OK I am at a gun show now and just had that hand guard in my hand. That ring needs to be turned off. Need to use a punch or strap to turn it. The set screw is for fine tune adjustment. Yours is jammed on really tight. Good Luck
    Logistics cannot win a war, but its absence or inadequacy can cause defeat. FM100-5
  • bisleybisley Senior Member Posts: 10,798 Senior Member
    See, that is the problem. The ring bottoms out against the receiver before it can be completely unthreaded. Describe the barrel nut - was it threaded for the hand guard, or smooth - can you take a picture, if you're still there?
  • Diver43Diver43 Senior Member Posts: 10,903 Senior Member
    Bisley you have PM
    Logistics cannot win a war, but its absence or inadequacy can cause defeat. FM100-5
  • Diver43Diver43 Senior Member Posts: 10,903 Senior Member
    7463d3cc739d058ebb2bfcb266d3536d.jpg482e9e066fa6c24b695ba1c56bacb50a.jpg

    As you can see the ring is threaded on then the tube to it.

    need to turn counter clockwise to remove it or whatever direction you can get movement. If everything is jammed up too tight you can remove the rail pieces and get to the gas block to
    remove it. You will then be able to remove the whole unit as one piece.

    If that does not work let me know and I have a reps phone number you can call.
    Logistics cannot win a war, but its absence or inadequacy can cause defeat. FM100-5
  • bisleybisley Senior Member Posts: 10,798 Senior Member
    I'm not able to work on it, right now, but I know the gas block will have to be removed.

    I'm not convinced that the gas block set screws can both be accessed by removing a rail section, but I hope that is the case.

    Thanks for your efforts, Diver. :up:
  • DoctorWhoDoctorWho Senior Member Posts: 9,496 Senior Member
    Somehow I doubt that you need to remove the gas block in order to do anything to it, while handguards have changed much since I was putting them together, it does seem less likely that the gas block would need to be installed after the handguard is installed.
    "There is some evil in all of us, Doctor, even you, the Valeyard is an amalgamation of the darker sides of your nature, somewhere between your twelfth and final incarnation, and I may say, you do not improve with age. Founding member of the G&A forum since 1996
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