[Arty Fo]

Next issue the sight I purchased to put on my AR is almost maxed out to the left when BZO at 30 yards. it shoots same at 100. It is a UTG sight maid by Leapers Inc. They claim it is to mil spec, and it is most likely an issue with the upper. I know they can claim whatever. The sight looks good and solid and very proportional when mounted. I would think that if it was a spec issue with the sight it would have to look out of proportion when mounted to require such a big adjustment left. what would I look for to see if it is the upper. I understand that UTG is not high end. I do not have another sight to try but may have to acquire one if that is my only option. It is not unshootable and actually shoots and holds good even if removed and reinstalled.

Please advise.DI5
Arty Fo... Out

 

[Hgunner]

Do you have iron sights and do they zero without maxing the windage adjustments.

 

[Arty Fo]

Irons yes on a flat top

it is about 5 clicks from being maxed at zero. that is the issue sorry I did not make that clear. The utg is a pictnary rail mount Iron sight.

 

[blackdiamond]

Is the sight an A-2 type that is pinned in conjunction (all one piece) with the gas block, or is it not pinned and screwed down which incorporates the sight and the gas block together (all one piece)? You will notice that the hole in the gas block (sight assy) is bigger than the hole in the barrel. This allows room for adjustment. It doesn't take much to offset the whole gas block/sight base to create the problem you are having. If it's not a pinned sight base and you have some latitude, try repositioning the gas block to center if the sight and gas block are all one piece. Very little adjustment will make a big difference. Let us know how it works out for you.

 

[Arty Fo]

Pined I believe

It is a standard A2 front sight. if it can be adjusted please advise.

 

[GARRARD]

Sometimes a bent barrel can create the problems you're describing. I would have a straightness gage ran through it and go from there, unless it's a fairly new rifle.

 

[ArmyCPT]

First thing I'd try is a new rear sight. UTG/Leapers is junk. It certainly isn't milspec, or for that matter even close. Magpul makes one out of mostly plastic components (the MBUS) that you should be able to pick for around $50. Others run higher, with Troy's BUIS being not only top of the line, but pretty much the highest cost item at around $125-150.

If it's not the BUIS, your front sight base may not be correctly aligned. Who made your upper?

HTH.

 

[Arty Fo]

new rifle

Sometimes a bent barrel can create the problems you're describing. I would have a straightness gage ran through it and go from there, unless it's a fairly new rifle.

The rifle is new.

 

[Arty Fo]

First thing I'd try is a new rear sight. UTG/Leapers is junk. It certainly isn't milspec, or for that matter even close. Magpul makes one out of mostly plastic components (the MBUS) that you should be able to pick for around $50. Others run higher, with Troy's BUIS being not only top of the line, but pretty much the highest cost item at around $125-150.

If it's not the BUIS, your front sight base may not be correctly aligned. Who made your upper?

HTH.

I do not know who made the upper.

 

[blackdiamond]

It is a standard A2 front sight. if it can be adjusted please advise.

Ah, I was under the impression you installed the gas block/front sight. The A-2 front sight bases are typically pinned via the barrel slots which pretty much aligns itself. Since your gas block/sight base was new and already installed when you received it, if it is not correctly centered I would be surprised, but that is still possible. And if that is the problem, I'm sure there is a way to correct it, but I couldn't tell you how. I tend to agree with ArmyCPT in that the rear sight is suspect. Maybe you could borrow a rear sight or carry handle to troubleshoot the problem. I installed a YHM gas block/sight that does not utilize the pins and had a similar problem until I realigned the gas block/sight base ever so slightly; but again, it is not the A-2 type that uses the pins.

 

[Arty Fo]

Replace the rear

I will replace the rear and will let you know what is up.
Thanks for the help.

 

[Hgunner]

Try a new rear sight, but I also had to send an AR back a couple of years ago for a simular issue, the front sight was canted slightly.

 

[ArmyCPT]

Since your gas block/sight base was new and already installed when you received it, if it is not correctly centered I would be surprised, but that is still possible. And if that is the problem, I'm sure there is a way to correct it, but I couldn't tell you how

It happens.

Link: http://www.m4carbine.net/showthread.php?t=807

 

[CHARLIED308]

If the detachable rear sight is machined true, there may be an issue with the front sight base not being properly indexed and canted to one side. Unfortunately, many of the firearms manufacturers believe that 13 clicks within dead center windage is acceptable. In my experience most of the time the rear sight requires too much left windage to center my shot groups. In most cases the front sight base is not properly indexed when it is attached to the barrel during production. I have adjusted 20+ AR style rifles over the years to correct the problem.

Here is the procedure:

1) I lock the upper in a fixture and level the upper using the picatinny rail area as a reference.

2) I take a caliper and check the difference between the inside edge of the rear sight assembly and rear peep sight on both sides. I record the measurements and calculate how much distance in thousandths of an inch I would have to move the rear sight to bring it to zero windage.

3) I check the distance from one side of the front sight base using a fixed area as a reference. You can use a caliper or dial indicator to take this measurement. I keep the upper receiver locked in for this measurement and ensure the flat top (picatinny rail) is level when I take this measurement.

4) I loosen the barrel nut and move the front sight the same distance necessary to zero the rear sight. I move the front sight base in the opposite direction that I would have to move the rear sight. If the rear sight is adjusted well off center to the left, I move the front sight base an equal amount to the right. If I have to remove material from the slot that the gas tube passes through on the upper receiver to make my adjustment, I remove just enough material to get the job done.

5) I tighten the barrel nut to the correct torque plus whatever it takes to center the gas tube through the barrel nut without touching the barrel nut when I push the gas tube through. I prefer that the gas tube does not touch anything and it lines up with the bolt carrier key (aka gas key) without binding. Use a piece of wood dowel rod to hold the front sight base in position when torqueing the barrel nut.

6) I move the rear sight to zero windage and fire a few shots to confirm I am at zero windage. Remember to hold the front sight level and zero the top of the front sight pin dead center in the rear peep.

I repeat the whole process if I am not within 3 clicks of zero windage.

I would not pitch a barrel if the rear sight will not zero within a few clicks of center when I first take it to the range. The front sight base might look a bit out of plumb while holding the weapon upright and looking at the rifle, but the sight picture looks just fine when you fire the weapon. I have performed this zeroing technique to quite a few rifles and some of them would shoot sub MOA groups out to 300 yards. Setting a rifle up this way gives you a maximum amount of windage adjustment to compensate for changes in wind and light while shooting at longer distances.

If you have any questions, feel free to PM me.

 

[DannyG]

Sights...

I had a brand new Bushmaster barrel/ upper that had the same issue , but with fixed A2 sights. They had issues of installing the front sight base canted, resulting in rear sight adjustment being WAY left. I sent it back to them, they fixed it quickly ( and for free), it's been fine since then. Point being, the issue was with the front sight base, not the rear.
HTH,
DanG

 

[CHARLIED308]

In almost all cases where I had to re-index the barrel the rifles were built by Bushmaster.

 

[jim-analog]

Greetings,

Hi CharlieD! Question regarding your procedure for adjusting due to front site rotation..............

As I see it, there isn't all that much rotational movement possible between the upper receiver slot and the locating pin on the barrel extension. Do you widen the slot to get sufficient range of adjustment?

Also, it seems if the barrel is rotated more than some degrees, at some point the bolt lugs will no longer align. I mention this as I just had a new barrel with an incorrectly placed pin; this prevented the bolt from closing at all; it really wasn't that far off either. I no longer have the barrel here to measure; forgot to do that before sending it back.

I'd appreciate your comments. Thanks!

Regards, Jim

 

[CHARLIED308]

Jim,

You bring up a very good point. There is a slight amount of rotational play between the bolt and carrier after the bolt moves into full battery. If the front sight base needs to rotate 0.030" clockwise while viewed from the rear sight and the receiver slot the gas tube passes through only allows me to move the front sight base 0.020", I'll remove 0.010" material with a pillar file from the side of the slot. I cannot remember ever removing more than 0.015" or so and that was only on one rifle. Many times on a problem rifle, when I view the gas tube while looking through the bottom of the upper receiver with the bolt locked open, I'll observe the gas tube is off center with the barrel being indexed too far counter-clockwise when the barrel was installed. That would be the direction the barrel would move when the barrel nut was tightened at the factory. I would also notice a slight amount of binding between the gas tube and bolt carrier key when slowly cycling the bolt.

If I remember correctly, moving the front sight clockwise 0.006" shifts the Point of Impact a little more than 1 Minute of Angle to the left on a carbine, so a 0.030" front sight shift would move the Point of Impact about 5 MOA. I haven't had a rifle that I adjusted be more than 3 clicks windage from the zero windage mark on the rear sight assembly after re-indexing the barrel without removing any material from the receiver slot. I always check for smooth engagement of the bolt into the barrel extension before firing the weapon.

Even when installing a new barrel on an upper, I always take the extra time to hold the barrel with a wood dowel rod inserted in the front sight base and keep the gas tube centered in the slot on the upper receiver. A majority of the time my zero won't be too far from zero windage on the rear sight assembly. If your measurement indicates you have to move the front sight considerably more than the upper receiver slot would allow, you may have to purchase a new front sight base with allen screws and make your adjustment that way.

A critical area to check is the gas tube to bolt carrier key engagement/alignment. The engagement should be smooth without any indication of binding. Any binding will cause malfunctions.

If I were Arty Fo I would remove the UTG sight, borrow a detachable carry handle, attach it to my rifle and shoot it before I made any changes to the upper.

Hope this helps.

Charlie D

 

[jim-analog]

Greetings,

Hi Charlie D! Thanks much for the detailed explanation. Guess I wasn't realizing how small a rotational movement of the barrel resulted in shift in the site view.

I'm curious as to just how much leeway there is before the lugs don't lock up correctly. I just had to return a new (otherwise very nice) target barrel due to a mis-positioned locating pin. I really couldn't even see that it was off that far, but the tech at Brownells was able to determine that was the cause of the no lock up situation.

Thanks!

Regards, Jim

 

[M14]

I had a brand new Bushmaster barrel/ upper that had the same issue , but with fixed A2 sights. They had issues of installing the front sight base canted, resulting in rear sight adjustment being WAY left. I sent it back to them, they fixed it quickly ( and for free), it's been fine since then. Point being, the issue was with the front sight base, not the rear.
HTH,
DanG

Same problem for me with a Colt, thou I was not as lucky as you. After 3K rounds thru the rifle, the bolt carrier was taking chunks out of the inside of the upper. Colt replaced the upper and reused my barrel. This fixed the problem with chunking the upper, but now the front sight was canted and required near max adjustment of the rear. Sent back to colt and they installed a new barrel on the new upper - same problem. Colt would do nothing more and said the condition was normal, which is BS since the rifle had no problems with the sights originally.

Needless to say, I no longer own any Colt products.