If the barrel is properly indexed, and the sights are not canted what other causes would make a barrel shoot to one side?

What about a bent barrel?

M4-AK

A bent barrel could do it. Holding the gun off level can also do it.

Holding the rifle in a canted way (within reason) would not be too noticeable at 100 yards.

Your sights (or barrel) are not indexed well or your rear sight needs adjusting,

If you are using a sling, and applying to much sideways pressure.
Or, yeah a bent barrel.

Could be the barrel/reciever interface puts the barrel at a slight angle wrt the receiver. The face of the receiver or shoulder on the barrel extension only needs to be off by a fraction of a mil to move the front sight significantly.

Could also be the barrel extension is at a small angle wrt the barrel.

Shooting from a rest, this rifle requires 13 clicks left to center. Front site is canted slightly right. If sight were not canted, would require even more clicks. It's a heavy barrel but I suppose even they bend or could be bent to begin with. Upper was bought used and cannot contact the seller. Looks great, shoots great other than the windage issue.

Reading here, my problem could be:
1. Bent barrel
2. extension problem
3. receiver interface problem.

How could that be determined, and what kind of solutions would fix those.

1. Can the barrel be easily straightened.
2. Can one see an extension problem?
3. Can one see a receiver problem?

If a part needs replacing, don't want to replace the wrong part. I don't want to buy a barrel when it's the receiver etc.

Help!!!

M4-AK  [smash]

If you have put on an aftermarket compensator that could be it.
I have seen several sub MOA rifles turn into shotgun pattern shooters after one was installed.
After re reading your last post, A front site cant, will cause the rifle to shoot to the opposite side.
FS right cant = round impacts left.

Yes so if my cant were corrected it would shoot even more right. No I don't have a compensator on it.

M4-AK

As Tweak once posted,

Hold only the upper receiver in your hand, and use a leather mallet to rotate the barrel (extension) in the upper receiver to fix the problem.

You want to strike the front sight tower just above the barrel and drift the barrel in the upper to the left to allow the rear to be centered (and the rifle zeroed).  

The blow to the front sight tower will rotate the entire barrel and extension in the upper receiver socket, not just the tower alone. When you index this way with a leather mallet, do it at the range.  You will want to give the tower a love tap, and then fire for effect until you have indexed the POI for the rear sight at dead center.

Also, Factors such as bullet weight and ammo type (brand) will change the POI, but even with the rear sight 13 clicks off center, the rifle is still in Mil-spec for correct factory barrel index.

It's already canted in the direction that would correct the error. To move it more would create additional cant to the right.

I went through this a couple months ago, and the only scientific method to see what the problem is, is to buy or borrow a laser bore sighter, or take to a smith so he can check it. You can get an Aimshot from Sportsmans Guide for about $63.00 plus shipping. I recommend getting one, it will be useful in the future. This will show you the actual alignment of the barrel in relation to the sights. If it's off, it will be very obvious. If it's dead on, then either trigger creep is excessive (causing you to pull right) or you are just pulling unconciously. That's my 2. Hope that helps. [thinking]

Got a rockriver two stage. No creep there. Yeah one of those laser things sounds like a useful tool.

M4-AK

Sorry about posting the wrong direction to correct the sighting, I had just drove for three days straight to get back home out of Florida, and was a little road blind when I posted last night.

The front sight has to go to the right as you are looking down the barrel from the butt stock (same direction that you are going to move the rear to center).

The one thing to watch is once you have the barrel/tower in the correct index, check the bolt to make sure that you haven't twisted the barrel extension out of alignment and the bolt binds up on the lugs when it is locking/unlocking. With the rear sight only 13 clicks to zero, there is little worry about binding, but don't forget to check.

Regarding front sight index, the relationship of the front sight to carry handle is only for reference.  To fine tune, you will need to move the barrel/tower in the upper receiver to get the front sight tower into the correct position for a rear center zero. Tweaks method works well/faster than pulling the barrel nut and shimming, plus you don't need to buy $60 in tools.

If the barrel is bent/cocked in the socket, when you sight the rifle in for 100 yards, as you shoot out to the 300 yard range, the rifle will start to shoot off to the right again. If this is the case, pull the barrel and spin it with a mic/rotation jig to see if it is truly bent, or the barrel extension to socket is the problem.  Worse case scenario is that you need to replace either the barrel or upper receiver, which would set you back $125 at the most for parts.

Also, as I stated before, 13 clicks off center is still within mil specs, but I understand that you are like the rest of us and want the rifle perfect in every way, including the rear sight dead center when zeroed.

Bring me up to speed on who the upper is from, or who built the upper and what brand of parts where used.

P.S. Just to rub salt into the wound, I just saw that you are located in Florida, had I caught this post a few days sooner, I could have just taken a look at the rifle when I was down there.

It's a bushy hbar 20" bought used, and looks great, shoots fine, and believed to have come off a new rifle. I wonder if Bushy would fix it even though it's got no warranty. I bought it for a target upper, so the 13+ clicks bothers me.

M4-AK

I have to move the sight 13 clicks left to correct for it shooting right. Front site is almost square, but is slightly right. So moving the sight square should mean even more clicks. Haven't removed the nut yet but a friend has the tools to do this.

Thanks again
M4-AK

The front sight moves towards the POI to zero, the rear moves away to center.  If the rifle is shooting right, then the front tower needs to be indexed/move to the right even father.  The fact that it is notable that the sight is canted right (off receiver center-line) to correct the POI leads me to believe that the barrel muzzle line is not on the same center line as the upper receiver.


Best bet is to pull the barrel and check the upper barrel socket to make sure that there is not a bur that is canting the barrel off center line of the upper receiver(may be as simple as chucking the upper up in a mill and trueing the socket end) , check the muzzle for signs of a bur that may be deflecting the bullet on the way out (or just re-crown the muzzle), and chuck the barrel in a jig/stand (lathe works the best) that will allow you to spin the barrel using a free stand mic and make sure that it is not bent(live center suport works well to true the barrel). If you have access to the tools, the barrel can be pulled and every thing checked out/fixed in less than 20 min.


Bottom line is if the sight is already canted to the right (noticeable) and you need to move it even father to correct the sights, pull the barrel and check everything out.

Post your results and we can get up and fixed in no time, or at least tell you where to send the defective part(s) to be corrected.

------------------------------------------------

Also, You stated that you are using the rig as a target rifle.  If you are slinging up the rifle to zero, without a DCM float tube, the sling pressure on the barrel can be causing the problem.  Its best to just bench the rifle until you solve the problem, then re-zero for sling pressure (if you can keep it constant) or install a DCM tube system and forget about the effects of sling pressure to the barrel.  

Also to add, since you are using the rig as a match rifle, your going to be out shooting the stock barrel in a very short time. Add to the fact that when it comes to doping wind, you going to be adjusting the the rear sight all over the place. The fact that a lightly canted front sight is not going to really matter as long as the barrel is not bent (sight adjustment for a bent barrel at diferent ranges requries skills beyond a ZEN master).


Personal, I would pull the barrel, check everything out, and then wait to get a dead center zero (tower index) until I found the hand load the works in the rifle.  I have found that going from 55 grain to 62 plus seem to shot to the left on half of my target rigs (barrel whip).  At 13 clicks using standard sights, the shot is only 6 1/2' to the right. Considering that changing loads on a few of my rifles can result in the POI changing 3" to 4" with the secret load, the front sight may be indexed correctly on your rifle for the new designed loads.

I appreciate your taking the time to respond. I'm shooting off a rest with 55gr UMC to sight in and I'm shooting at 50yds. I'm not using the sling.

When you say the socket, your talking about the recess in the receiver, or where the extension fits to the barrel? Also how does the extension come off? is it threaded or pressed? Haven't taken one apart yet.

Thanks again
M4-AK

Pull the hand guards, and then punch out the gas tube roll pin in the sight tower.  The gas tube may be a bitch to get out of the tower if the upper has been shot a lot, but the tube should pull straight forwards towards the receiver, then twist it and pull it back past the sight tower (carrier out of the rifle).

Put the upper in an upper vise block, then put the barrel wench on the barrel nut and turn counter-clockwise. Once the nut is spun all the way free, pull the barrel straight out without twisting.  The barrel extension has a pin on top that mate to the upper receiver barrel socket slot.

The barrel extension is installed at 175lbs to the barrel, so don't even thing about trying to remove it from the barrel. If you did remove it, then you would need to re-index the extension with the front sight tower.

The areas to check are the barrel to make sure it's straight, the lip of the barrel extension socket on the upper receiver to make sure that it is square and lip bur free, then the mating surface inside the barrel nut to make sure that it is not packed with crap.  Don't try to remove the delta ring; you would have to remove the front sight tower to get it off the barrel any way.

As for re-installing the barrel, lube the threads, then tighten the nut to 35lbs, then loosen and retighten for three times.  On the third time, hit the 35 lbs mark, then check the nut spine to see if the gas tube will pass threw. If the nut spine is blocking the tube, tighten the barrel nut more, but do not exceed 80lbs.

A sight index bar works great to get the front sight tower in the correct index position, but if you don't have one, a piece of string will work to get the tower close to the correct index. Just run it threw the rear sight centered, and tie it off on the front sight. When the sight tower is in the correct index position, the string should be centered in the carry handle (your just going for close to correct index, the final index is determined by live fire).  

Also, unless you want to loosen the barrel nut another time to re-index the sight tower for fine-tuning, the leather mallet trick will drift the entire barrel in the upper receiver socket at the range to get the sight indexed/zeroed. just remember to only hold the receiver when you love tap the front sight tower. This will transfer all the impact energy to slipping the barrel in the upper receiver, and not mashing the tower pins against the tower and just drifting the tower on the barrel.

Hope this helps.

P.S. I type at around 70 words a minute and the rifle is second nature to me, I have been shooting them since 1968.  Although it may appear that I have spent a great deal of time regarding your post, your problem is just the same old thing that has occurred here may times here at AR15.com.  If I want to get real lazy, I could have just re-directed you to some of the old posts on the subject.

Also, get/reload some real ammo.  With the UMC ammo, you will be lucky to even keep the shots on the paper at the 600 meter mark.

Dano:

Tied the string last nite. Couldn't find evidence that the site is off to the right. The string looks straight. I believe it may have just been an optical illusion due to the shape of the ears on this site. There for a slight whacking may remove some clicks from the windage.

So the easiest thing for me to try was to whack the sight tower with a large rawhide mallet. Whacked the heck out of it 5 or 6 times to move it right. I'm unsure if I moved anything until I go to the range. Will take the mallet with me. (Although one will appear to be a kook knocking the hell out of your firearm with a mallet on a crowded range.)

Failing success with windage correction there, will have my friend remove the barrel from the upper and we'll examine it for burrs next.

I will keep you posted.

Thanks
M4-AK

Don't feel like an idiot giving the tower a blow at the range.  Anyone who knows about the Ar-15 will know what you doing.

Also, wait until you get to the range to adjust any more, your going to be surprised on how little you need to slip the barrel/tower over. Chances are you rotated the barrel too much already.  

P.S. If you think taking a leather mallet to the ar-15 tower at the range is strange, you would freak out on how I adjust the barrel/front sight on a HK-91 clone to get the sights zeroed.  The problem there is that when the front sight is installed, it is pin/brazed to the barrel.  The heat can cause the barrel to slightly bend at the sight tower, and pulling the barrel is not an easy option.

To bring it up to speed. Was 13 clicks left. Beat on the sight tower with a rawhide mallet 5 or 6 good whacks. Dano thinks I may have moved it too much.

Went to the range. Doggone it still exactly 13 clicks left. It hadn't moved a bit. So I took out my trusy rawhide and just tried to kill that da**ed sight.

Put it together and shot some more and  behold 6 clicks right. Could have been satisfied with that but whacked on it again but not as hard and no change. Removed the lower and one more good whack.

SUCCESSS... MECHANICAL DEAD CENTER.

p.s. The moral of the story is that you need to add a rawhide mallet to your AR sight tools.

M4-AK out
Thanks Dano...  [smash]

Sounds like you got it zeroed, depending on how much torque was used to install the barrel nut and index will depend on how much force it takes to drift the barrel in the upper socket.

P.S. I'm 6' and 235lbs.  A love tap to me is when you chance down a habor seal on a beach with a baseball bat.  Sounds like you just needed to man up and stop girly swinging to get the job done.

Had the same thing.. Bushy FAQs had it there also, said the barrel index pin may be bent. I removed the barrel and it looked fine. I pulled the pin out and rolled it on th table and sure enough it wouldn't roll it was bent so much. bought new pin ($1.50 Bushy part 9349054bip) installed and everything worked. My guess it that hitting it bent it back the other way. would it weaken the pin to much?
Mike_

Badboy,
The pin is just used to index the barrel in the receiver.  Depending on how the barrel was tightened, the pin can be bent.  If the barrel is vise clamped, then the barrel nut tightened, this transfers a lot of the torque threw the pin.  If an upper vise block is used, the pin is not really affected.

As for indexing the barrel/front sight for a dead center zero, it needs to be done under live fire, and you can either pull the barrel and rotate the barrel in the upper, or just use the leather mallet to do the same with the barrel nut still tightened down.

P.S. As for the pin, most are not heat treated, and can be straightened if needed.

Isn't the pin theoretically just an aid for indexing, not for retention. In other words, the pin could be just removed and it aligned by sight?

M4-AK

Yes and no.
If you have a barrel in which the front sight is canted (out of alignment) with the extension pin, then if you tried to rotate the barrel around, you may end up with the front sight straight, but the barrel extension rotated around to the point that the feed ramps and the lugs are out of alignment with the bolt, causing the bolt to crash into the face of the lugs, or bind up on unlock.

Also, the pin is draw back to the days when the method to install the barrel was to vise the barrel, before the upper vise block was designed.