Quad rail not aligning with upper receiver

[TripleDigitRide]

I'm assembling an AR for a friend, and I can't seem to get the quad rail and upper receiver to line up any better. I think I'm trying everything, but I very well could be missing something. It will line up, until I tighten the retaining screw in the bottom of the quad rail.

[Jct1911]

Put something that mounts to both rails on it. I usually use a QD mount aim point.

[TripleDigitRide]

Wouldn't this create an issue with achieving proper alignment of the BUIS? Edited April 20, 2015 by TripleDigitRide

[broox]

Isn't that why sights are adjustable?

[DMark]

Who is the maker of the rail?

 

Who is the maker of the upper?

[TripleDigitRide]

The upper is the TGO CMT upper, and I believe the rail is an inexpensive Omega. I'll double check that.

[TripleDigitRide]

Isn't that why sights are adjustable?

My thoughts, but he's concerned about it.

[BigK]

It looks like the barrel nut has gas tube holes, so you you clearly had to time the gas tube to get it through the barrel nut. I don't see how it could be anything but the mfg drilled the hole off center. I can't imagine you could turn the barrel nut enough to compensate and still line up the gas tube.

I'd send the rail back and insist that they pay return shipping.

[TripleDigitRide]

It looks like the barrel nut has gas tube holes, so you you clearly had to time the gas tube to get it through the barrel nut. I don't see how it could be anything but the mfg drilled the hole off center. I can't imagine you could turn the barrel nut enough to compensate and still line up the gas tube.

I'd send the rail back and insist that they pay return shipping.

Yes, the barrel nut has holes for the gas tube. I don't think there's enough room for adjustment to compensate for the amount the the rails are offset.

[Dolomite_supafly]

It looks like the barrel nut has gas tube holes, so you you clearly had to time the gas tube to get it through the barrel nut. I don't see how it could be anything but the mfg drilled the hole off center. I can't imagine you could turn the barrel nut enough to compensate and still line up the gas tube.

I'd send the rail back and insist that they pay return shipping.

The holes for the gas tube have nothing to do with the tube. The tube screws onto the nut. There is nothing wrong with the tube itself. You tighten the barrel nut until the gas tube hole lines THEN you screw the tube onto the nut and align it before tightening the locking ring.

This happens all the time. The way I fix it is make sure the receiver is secure then barely tighten the nut with the tube slightly leaning to the ejection port side. Then either grab the tube, use s strap wrench or a vertical grip and twist the tube the right direction the last little bit.

Matter of fact I do not use wrenches on that style of tube at all. The wrenches don't grab well enough.

[Dolomite_supafly]

If you want give me a call and I can talk you through it.

I have installed at least 10 similar rails and if the last thing you do is tighten the ring things rarely line up.

[BigK]

The holes for the gas tube have nothing to do with the tube. The tube screws onto the nut. There is nothing wrong with the tube itself. You tighten the barrel nut until the gas tube hole lines THEN you screw the tube onto the nut and align it before tightening the locking ring.

I only mentioned it because to me it looked like it might be misaligned by too much for him to be able to turn the barrel nut enough to line up the retaining screw without damaging our misaligning the gas tube.

I see what you mean, though. Edited April 20, 2015 by BigK

[Dolomite_supafly]

With that setup there is not any retaining screws. Only the tube and a "jam nut" to hold it in place.

[TripleDigitRide]

You tighten the barrel nut until the gas tube hole lines THEN you screw the tube onto the nut and align it before tightening the locking ring.

I thought that's what I did.

I tightened the barrel nut, installed the gas tube/gas block, installed the muzzle device, screwed on the quad rail, installed the retaining screw on the bottom side of the rail, then tightened the locking ring.

Hmmm! As I'm typing this, I wonder if I should have tried tightening the locking ring before installing the retaining screw.

When installing the rail, I was able to screw it on enough so that there was almost zero gap between the rail sections. However, this would not allow me to install the retaining screw, so I had to back the rail off one turn. For some reason, I am thinking the retaining wouldn't screw in with the rails properly aligned, but I'll go back and double check.

[TripleDigitRide]

With that setup there is not any retaining screws. Only the tube and a "jam nut" to hold it in place.

The retaining screw looks like the one pictured here... Half threads, half nipple.

Edited April 20, 2015 by TripleDigitRide

[maroonandwhite]

I thought that's what I did.

I tightened the barrel nut, installed the gas tube/gas block, installed the muzzle device, screwed on the quad rail, installed the retaining screw on the bottom side of the rail, then tightened the locking ring.

Hmmm! As I'm typing this, I wonder if I should have tried tightening the locking ring before installing the retaining screw.

When installing the rail, I was able to screw it on enough so that there was almost zero gap between the rail sections. However, this would not allow me to install the retaining screw, so I had to back the rail off one turn. For some reason, I am thinking the retaining wouldn't screw in with the rails properly aligned, but I'll go back and double check.

I have one of the Omega rails on mine. My locking nut has slots in it rather than holes though. At first I ran it all the way in so there was no gap but ended up running out out one turn so the rails lined up evenly. Doing that I was able to put a scope mount on to bridge the gap and line them up. I then tightened the lock ring down followed by the set screw. Mine seems to be pretty tight. It does seem the the set screw had to fight's it's way down while I was turning it though.

 

With all of that said I will probably go for a different mounting style guard on the next build. 

[TripleDigitRide]

I have one of the Omega rails on mine. My locking nut has slots in it rather than holes though. At first I ran it all the way in so there was no gap but ended up running out out one turn so the rails lined up evenly. Doing that I was able to put a scope mount on to bridge the gap and line them up. I then tightened the lock ring down followed by the set screw. Mine seems to be pretty tight. It does seem the the set screw had to fight's it's way down while I was turning it though.

With all of that said I will probably go for a different mounting style guard on the next build.

The "holes" in the locking ring are just dimples. It also has slots.

I have a feeling I'm going to need to do the same as you did. I'll tighten the locking ring first, then the retaining/set screw, even if I need to use a little extra persuasion. Edited April 20, 2015 by TripleDigitRide

[maroonandwhite]

The "holes" in the locking ring are just dimples. It also has slots.

I have a feeling I'm going to need to do the same as you did. I'll tighten the locking ring first, then the retaining/set screw, even if I need to use a little extra persuasion.

My guess is that those little ridges for the set screw to sit don't line up exactly. I honestly didn't check on mine because it finally felt like it bottomed out and it was solid so I left it alone.

[TripleDigitRide]

My guess is that those little ridges for the set screw to sit don't line up exactly. I honestly didn't check on mine because it finally felt like it bottomed out and it was solid so I left it alone.

That's what I'm suspecting.

[mikegideon]

Hit that sucker with a BFH. That'll do it :)

[Lumber_Jack]

Back off jam nut and take out retaining screw. Aligned the upper rail. Best way is with a mount over the gap. Screw jam nut tight, put in retaining screw.

This is the same method YHM has used for years. The rail needs to be free spinning on the barrel nut threads for proper alignment. I would turn the rail until it makes contact with the receiver and the reverse until it's aligned straight Edited April 20, 2015 by Lumber_Jack

[maroonandwhite]

Back off jam nut and take out retaining screw. Aligned the upper rail. Best way is with a mount over the gap. Screw jam nut tight, put in retaining screw.

This is the same method YHM has used for years. The rail needs to be free spinning on the barrel nut threads for proper alignment. I would turn the rail until it makes contact with the receiver and the reverse until it's aligned straight

From what I can tell these Omega rails are mainly copies of the YHM stuff. Good stuff for the money though. Think I paid around $40 for mine.

[TripleDigitRide]

Back off jam nut and take out retaining screw. Aligned the upper rail. Best way is with a mount over the gap. Screw jam nut tight, put in retaining screw.

This is the same method YHM has used for years. The rail needs to be free spinning on the barrel nut threads for proper alignment. I would turn the rail until it makes contact with the receiver and the reverse until it's aligned straight

If I screw the rail to the point that the rails are even and touching, the edge of the barrel nut partially blocks the retainer/set screw hole, barely allowing the screw to get started. This is why I had to back the rail off by one turn, leaving a small gap between the upper receiver and quad rail.
I'm going to fool with it again this afternoon. I'll report back.

[TripleDigitRide]

I used the optics base trick. I mounted it where the two rail sections meet, then re-tightened everything down. Worked like a charm. Thank you. 

[Jct1911]

I used the optics base trick. I mounted it where the two rail sections meet, then re-tightened everything down. Worked like a charm. Thank you.

Sorry, I should have added more detail but you figured out what I meant. Glad it worked