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Posted: 2/10/2014 4:26:01 PM EDT
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So I have this rifle that I received few weeks ago and have shot once (approximately 120 rounds) and I was handling it tonight and noticed that if I "turn" the front end by grabbing the handguard or the foregrip, it will rotate maybe 1/4 of an inch back and forth. It looks like it's rotating at wherever the free float handguard goes into the receiver.
Is there something I can check that would be an obvious cause for this? I'm assuming it's not normal and it shouldn't have any amount of play whatsoever. |
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I did some tinkering and found the following...
I removed this bolt on the underside of the rail which loosened it completely: http://i.imgur.com/1Up53RR.jpg And I noticed that this ring in the red square wasn't fully tightened against the receiver, so I tightened it up against the receiver: http://i.imgur.com/WrNqI7L.jpg After I did that, the rail on the handguard spun almost a complete rotation around again and the receiver lined up and now sit flush: http://i.imgur.com/vWj9Pfu.jpg Is that how it should be? Before there was a very noticeable gap between the rail on the receiver and the rail on the handguard. |
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Do you mean that I should maybe back the handguard out and back the jam nut away from the receiver again, so that there is a gap between the handguard rail and receiver rail?
I believe it is a UTG Free Float Handguard. Tightening that ring up against the receiver and giving the handguard another full rotation so that the rails are butted up against eachother seems to be the only way it sits without having a little bit of left-to-right play. I don't know if I should have someone look at it or not. I also noticed that the handguard rail sits just a splinter above the rail on the receiver where they meet, but it angles down gradually to maybe a couple of centimeters as you get towards the barrel end of the handguard rail. In essence, if I place a straight edge across the top, the handguard rail starts to dip a little bit as you get further away from where it meets the receiver rail. |
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Your barrel nut is loose. That play you feel is the barrel but turning with-in the play available via gas tube.
By tightening the jam nut against the receiver you essentially are jamming the barrel nut a well as the free float rail. This will cause damage. You will cause irreparable damage. You need to have someone who knows what they are doing tighten down the barrel nut correctly and then they can play with the free float as well. |
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Quoted:
Your barrel nut is loose. That play you feel is the barrel but turning with-in the play available via gas tube. By tightening the jam nut against the receiver you essentially are jamming the barrel nut a well as the free float rail. This will cause damage. You will cause irreparable damage. You need to have someone who knows what they are doing tighten down the barrel nut correctly and then they can play with the free float as well. Would the barrel nut being loose cause the barrel to be loose as well? It didn't appear that the barrel itself was loose/twisting at all, just the handguard around it. |
| I found a video on Youtube that will give you the basic idea of the installation process. |
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Thanks, I actually looked at that one early this morning and the part where he screws that ring all the way back to the receiver and then tightens the handguard up to it is what makes me think mine just wasn't tight enough to begin with, but I don't know. I thnk I'll probably take it to a gunsmith tomorrow after work and have them look at it just in case. |
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Yep, Gas block/gas tube needs to be pulled, the float tube set screws removed, the tube removed, then the barrel nut tightened correctly this time around before the rest is reinstalled.
As it is now, the barrel nut is not correctly tightened to hold the barrel tight in the upper receiver barrel socket, and instead you at tightening the tube to the receiver to wedge tighten the barrel nut away from the upper barrel socket face instead; ending with a loose barrel in the upper receiver socket instead. |
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For what it's worth, when I took the set screw out that keeps the handguard from completely spinning around, this is what it looked like through the hole. The "teeth" on that wheel looking thing with the "sockets" looks all chewed up. The twisting is limited to the handguard between the two walls inside this indentation where the set screw is hitting. I don't see at all that the barrel itself is moving at all in any of this.
http://i.imgur.com/IqgzlBU.jpg http://i.imgur.com/d5jiyHZ.jpg |
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If the barrel nut is tight/correctly indexed, then the marring of the tip of the set screw to the channel below it looks normal'ish.
So the question comes down to if the set screw was loctite in to keep it tight, or was/is the problem that no loctite was used, and reason that the float tube set screws cam loose from the barrel nut detent instead? |
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Quoted:
If the barrel nut is tight/correctly indexed, then the marring of the tip of the set screw to the channel below it looks normal'ish. So the question comes down to if the set screw was loctite in to keep it tight, or was/is the problem that no loctite was used, and reason that the float tube set screws cam loose from the barrel nut detent instead? I'm guessing it's an issue where the set screw wasn't in either far enough or tight enough and it caused enough back and forth shifting to create a larger "gap" where the screw hits the indent and allowed it to develop movement. I just don't know if I should tighten that set screw as tight as I can to make it not move anymore or what. I can't find anything on a recommended torque rating for that set screw or anything. My assumption is that it shouldn't be much more than hand tight. Doesn't seem like that gun bolt channel is made of the hardest material so I don't want to crack it or something? I'm probably bringing it to an AR-15 armorer after work today just so I can have a pair of experienced eyes look at it and handle it in person. |
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And I noticed that this ring in the red square wasn't fully tightened against the receiver, so I tightened it up against the receiver:
http://i.imgur.com/WrNqI7L.jpg I believe the part in red is your problem. The retaining ring actually tightens against the hand guard and not the receiver. |
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Well before I moved it there, it was up against the handguard, but rotated it the other way up against the receiver when I thought that might be the problem. Unfortunately I tightened it a little too much and can't seem to rotate it back.
I'll let you know what the gunsmith says after I stop by after work and have them look at it. Hopefully it's just something easy and nothing is damaged. |
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http://i.imgur.com/IqgzlBU.jpg
http://i.imgur.com/d5jiyHZ.jpg Looking at these pics, especially the second one, it looks like the barrel nut is not properly installed, meaning it is either under or over rotated to be proper indexed. When looking at the bottom pic, it looks like the locking screw is favoring one side of the recess, as it is gouged on the top edge (top side in the pic). The area where the set screw will lock into is a relief where the gas tube passes through, if you had the free float tube off of the barrel nut and looked at the front of the barrel nut, you would see that the barrel nut is a series of holes on the face, those holes allow you to use a barrel nut wrench when tightening or loosing the barrel nut, but what ever hole lines up top dead center will be the hole that the gas tube passes through with the hole in the receiver. When the barrel nut is properly aligned, the gas tube hole will be top dead center with the gas tube hole in the receiver, which will allow a little play in the gas tube (play being right and left). If the barrel nut is slightly off to one side or the other, the gas tube will be pushed off center and will not have any sideways play (left and right), or only have play to one side but not the other, thus resulting in a gas tube the will erode quicker due to rubbing inside of the carrier key (gas key). Now what makes me think the barrel nut is slightly off center, is that the set screw should recess into one of the gas tube holes dead center, and when that screw goes dead center it should not gouge the sides. Hopefully the gunsmith that you took it to, will properly index the barrel nut. CY6 Greg Sullivan "Sully" SLR15 Rifles TheDefensiveEdge.com (763) 712-0123 |
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Thanks for the information. I believe that is what happened as well and he seemed to know right away that might be the problem.
For what it's worth, after shooting there was a sorta-brownish dust all over the inside of the handguard. When I think about it, it's the same color as the gas rod. So maybe you are right, it was rubbing against something while I was shooting? Hopefully I'll be able to pick it up before the storm comes and he can give me good news that it's all better! |
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Got the gun back this afternoon. He said they basically took the hand guard off and had to re-tighten the barrel bolt and all that jazz and that it should be good to go now (that it was done the proper way).
Thanks for leading me in the right direction. Glad I had someone look at it! |
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