Posted: 3/7/2012 10:54:37 AM EDT
| Anyone want to share or help me reinstall my barrel on my AR. I had a new rail put on and the Smith took my barrel off to do it but now it sits slanted. It is about 1/16 inch closer to the top of the rail than the bottom. Just want to even it back out. Left and right side are equal but the top and bottom aren't. What I am looking for is a upper receiver vise block (I have a vise on my workbench but need the clamp), torque wrench, and barrel nut wrench. Let me know. I am near Yorkville IL |
| It is S&W M&P 15 OR. Best AR I own. The thing has always been top notch. I wanted to replace a quad rail I had on it but didn't have the tools so I sent it GAT Guns to have them do it. It took a week to get back and it looks like they overtightened the barrel nut a bit and it is pulling the barrel. They did a crappy job. My low pro gas block was completely loose so I had to tighten that and the flash hider was not tightened back on. It was hand threaded. I have done business there and like the place but I won't let one of their smiths touch one of my rifles again. The barrel was whatever barrel S&W puts on. They are chrome lined, 1/9 twist, MPI testted barrels. The rail is a TROY MRF 10 inch rail. The rail is square as can be. |
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It's hard to imagine how the smith could have gotten the barrel cocked in the upper receiver. The barrel extension typically fits the upper pretty snug and the barrel nut can only go on one way. There's not much there that could go wrong. I guess I'd have to see it to understand how the installation went wrong.
Have you tried shooting it? If the barrel is now canted up or down measurably, the elevation is going to show it. It's possible that the rail makes it look canted. |
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Quoted: It's hard to imagine how the smith could have gotten the barrel cocked in the upper receiver. The barrel extension typically fits the upper pretty snug and the barrel nut can only go on one way. There's not much there that could go wrong. I guess I'd have to see it to understand how the installation went wrong. Have you tried shooting it? If the barrel is now canted up or down measurably, the elevation is going to show it. It's possible that the rail makes it look canted. Agreed- the barrel really only goes on one way. The only way the barrel would be canted compared the the central axis of the upper receiver is if the receiver face is not true. Can't imagine any reason why the smith would've messed with that, so I don't understand. I suppose if the receiver threading was stripped out somehow (maybe due to improper application of lube on the nut/receiver threading), tightening down the barrel nut on bad threading could conceivably cause the barrel to cant? But it's taking quite a stretch of my imagination. Is the barrel still sitting parrallel to the axis of the receiver? If it is parrallel, but sitting closer to the top rail, that may just be because the rail wasn't designed to be symmetrical along the barrel. I don't have experience with the MRF rail, so I can't comment on that. However, IF the barrel is actually at an angle and no longer parallel to the axis of the receiver, DONT SHOOT THE RIFLE. they may have somehow introduced a bend on the barrel. (how? I have no idea...)
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| I have shot it and it shoots fine. The fact that the barrel is closer to the top of the rail has had no impact on accuracy. The low pro gas block still clears the inside diameter of the rail. It is only angled upward in the rail with a 1/16 inch difference between the top of the rail and the barrel and the bottom of the rail and the barrel. So if it moved 1/32 of inch downward it would be centered. I know it is not much but it is noticeable to me. The rail is one there straight. It is not crooked or cocked or anything so I suppose it could be the face of the receiver but wouldn't that be noticeable before I put this rail on? Wouldn't you be able to tell with the old handguard installed? They took off the barrel to take off the delta ring and then installed the barrel nut back on when installing the barrel. I am not sure why they didn't cut off the delta ring but I suppose I don't want a dremel going to work on my AR. The ff rail is the style that clamps on to the existing barrel nut. Any thoughts? My original plan was to just remove the barrel and re-install it but if anyone has any other suggestions let me know. Thanks |
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Quoted: I have shot it and it shoots fine. The fact that the barrel is closer to the top of the rail has had no impact on accuracy. The low pro gas block still clears the inside diameter of the rail. It is only angled upward in the rail with a 1/16 inch difference between the top of the rail and the barrel and the bottom of the rail and the barrel. So if it moved 1/32 of inch downward it would be centered. I know it is not much but it is noticeable to me. The rail is one there straight. It is not crooked or cocked or anything so I suppose it could be the face of the receiver but wouldn't that be noticeable before I put this rail on? Wouldn't you be able to tell with the old handguard installed? They took off the barrel to take off the delta ring and then installed the barrel nut back on when installing the barrel. I am not sure why they didn't cut off the delta ring but I suppose I don't want a dremel going to work on my AR. The ff rail is the style that clamps on to the existing barrel nut. Any thoughts? My original plan was to just remove the barrel and re-install it but if anyone has any other suggestions let me know. Thanks Gonna need pictures. Again, if the barrel is offcenter with the hand guards, but is still parallel to the axis of the receiver (perpendicular to the face), then it is fine. |
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Quoted: Ill get pics up in a little bit of the front of the hand guard and barrel. The barrel is good. It is installed properly and not bent or crooked in the receiver. It shoots great. Give me about 20 minutes for the pictures. The barrel may be closer to the top rail than the bottom, but is the axis of the barrel parallel to the axis of the handguard? |
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is it possible that the rail is not true to the upper reciever?
I'm assuming the upper is a flat top so do you have a straight edge like a good ruler? lay the thin edge of the ruler on the middle of the reciever down middle and the rail (like a scope sits) are there any gaps between the straight edge and the rail on the upper or quadrail? if there is it is the quadrail and not the barrel nut. |
| It is straight, flush, and not gaps. It is the first thing I checked when I noticed. The rail is and the top of the receiver is one straight piece. I have a lot of pictures inbound. the barrel and the rail are showing level. It is very confusing. Give me a couple minutes to get them loaded. |
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Quoted: It is straight, flush, and not gaps. It is the first thing I checked when I noticed. The rail is and the top of the receiver is one straight piece. I have a lot of pictures inbound. the barrel and the rail are showing level. It is very confusing. Give me a couple minutes to get them loaded. If both the barrel and HG are showing level relative to the receiver, then you should be fine. Some of the newer HG's aren't designed to be perfectly symmetrical relative to the barrel. My TROY TRX Extreme for example is slightly oblong, and has more clearance on the bottom than on the top.
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It is bizarre. The rail and barrel are on the same level plane, yet the barrel is closer to the top rail instead of centered Of course it will, your optics will be more in line with the barrel for a better zero if you think about it. If guns were designed the old way, the iron sights would only need to be about an 1/8 of an inch off the barrel for true accuracy 
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Quoted:
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It is straight, flush, and not gaps. It is the first thing I checked when I noticed. The rail is and the top of the receiver is one straight piece. I have a lot of pictures inbound. the barrel and the rail are showing level. It is very confusing. Give me a couple minutes to get them loaded. If both the barrel and HG are showing level relative to the receiver, then you should be fine. Some of the newer HG's aren't designed to be perfectly symmetrical relative to the barrel. My TROY TRX Extreme for example is slightly oblong, and has more clearance on the bottom than on the top. ok so you are saying that the rail itself may have been designed to give extra room at the bottom say for gas block clearance or something? |
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I think you might be seeing what is sometimes referred to as tolerance stack. While most mass produced parts are fairly precise nowadays due to manufacturing equipment and methods, nothing is perfect. In a non-critical situation such as the gap between the free float tube and the barrel, slight differences may be present. As long as everything fits and functions properly, I wouldn't worry about it.
From what I can see, the gunsmith who assembled the upper didn't do anything wrong and I don't think you will gain anything by disassembling and reassembling it. |
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Quoted:
I think you might be seeing what is sometimes referred to as tolerance stack. While most mass produced parts are fairly precise nowadays due to manufacturing equipment and methods, nothing is perfect. In a non-critical situation such as the gap between the free float tube and the barrel, slight differences may be present. As long as everything fits and functions properly, I wouldn't worry about it. From what I can see, the gunsmith who assembled the upper didn't do anything wrong and I don't think you will gain anything by disassembling and reassembling it. +1 I had the exact same issue with one of my former rifles. It was a 6.8 SPC RRA with a YHM Diamond Quad Rail. The issue was only cosmetic, and the rifle shot great. So I just forced my picky ass to forget about it. Ended up selling the rifle because 6.8 was too pricey for me. What was a pain in the ass for me was to get the rails lined up properly. |
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Quoted:
I guess that is my problem too. I am picky as hell. I guess a cosmetic issue of 3/32 of inch in barrel-rail alignment is not a big deal especially since all is square to the receiver and nothing is messed up. BTW Nolan i like your picture/avatar. haha thank you! |