Trouble sighting in AR

Discussion in 'Rifle Country' started by James Dietz, Mar 18, 2019.

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  1. James Dietz

    James Dietz Member

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    I purchased a new DPMS Oracle AR-15 flat top. Ordered the iron sights and now am real frustrated trying to sight it in.

    Vertical is fine. However with the rear sight dialed all the way to the left I am still shooting 3 inches to the right at 50 yds. I suspect that it is a problem with the alignment of the rail on the gas block but it is permanently mounted to the gas block.

    Is there any adjustment in the gas block?

    Thank you!
     
  2. troy fairweather

    troy fairweather Member

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    Can you take a pic from the back of the rifle. Looking down the sights but further back and up some.
     
  3. ponchh

    ponchh Member

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    Gas block probably not centered on top, you're gonna have to loosen that baby up and get it at 12 o'clock
     
  4. Coal Dragger

    Coal Dragger member

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    Not sure, is the gas block pinned, set screwed into dimples on the underside of the barrel, or does it clamp on the barrel?

    If it is pinned or set screwed, you are SOL unfortunately.
     
  5. troy fairweather

    troy fairweather Member

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    there is the rare chance the upper receiver is not true and the barrel is not pointing straight.
     
  6. DoubleMag

    DoubleMag Member

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    Verify both rear & front sights are correctly bottomed inside the slot. With sights mounted simply flip the rifle upside down onto a known flat surface such as the kitchen table. The sights will be supporting the rifle, and absolutely on the same level plane, no wobble. Well at least you hope. If there is no wobble while still supported by the sights i.e. upside down,place a small bullet level on a known flat surface location, such as the trigger guard.

    I have seen this before unfortunately and with that same company. Good luck!
     
  7. IndianaBoy

    IndianaBoy Member

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    EDIT Read this first -

    Your gas block is probably not pinned. I found this picture of an Oracle:

    15957-DEFAULT-l.jpg

    There are two or three set screws on the bottom of your gas block. They may have have some loctite on them. If so, you may need to put some heat on them to loose them. Remove your stock, sights and handguards. Loosen the set screws and set your rifle upside down on a known flat surface. Rotate your gas block carefully until it is perfectly level and on plane with your upper receiver. Add a dab of rockset or loctite to the set screws, and torque them back down. Don't monkey fist them. Use an allen wrench, not a screwdriver. Then you should be able to zero your rifle with irons.

    Do not be concerned about this small amount of rotation in your gas block from a function standpoint. Gas blocks are drilled with oversized holes that are larger than the gas port which is drilled in the barrel. This allows for some wiggle room when installing gas blocks to ensure that full gas is still available to cycle the rifle.

    Rotate your gas block but try not to move it fore or aft. It should still be snug against the collar that retains your handguards.


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



    I typed all of this below, when I thought you had a pinned gas block. I am not deleting it because it may be helpful to someone who has a pinned gas block.

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


    There is no adjustment in the gas block once it is pinned. However, there is a way you can true the gas block closer to the true center of your upper receiver. When your barrel is installed in your upper, there is a notch where the pin that is in the barrel extension sits. This pin almost always has some play from side to side. It can be shimmed, and the notch in the upper can be filed(if necessary), until the front sight post is trued to be square with the top of your upper receiver.


    If you do not have the tools to do this yourself, contact John Thomas at Retro Arms Works in Illinois. He does fantastic work, he is fast, and his prices are excellent. I have the tools to do it and would offer to do it for you but I am not licensed to do gunsmithing work. It is an easy job, but it is made much easier by years of experience.


    Since this work would require just the upper and that is not legally a firearm, you can ship it directly to him in a flat rate box without hassling about FFL issues.
     
    Last edited: Mar 19, 2019
    Mosin Bubba, Doc Samson and 340PD like this.
  8. IndianaBoy

    IndianaBoy Member

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    When the barrel nut is torqued, it will naturally pull the barrel clockwise when looking at the front of the upper receiver. This describes perfectly what you are describing with your sights being maxed out to the left and still not being zeroed. A small shim placed in the notch on your upper receiver would prevent the barrel from rotating as the barrel nut is tightened, and would correct your alignment issues.


    It's a 5 minute job with the right tools.
     
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  9. IndianaBoy

    IndianaBoy Member

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    Not true. He could also buy a clamping type gas block. Which are actually much more secure than set screw held gas blocks.


    He should not have to buy a new part to fix a new rifle, but he is not SOL.
     
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  10. IndianaBoy

    IndianaBoy Member

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    If your barrel is dimpled for the set screws to nestle into, which I doubt, then you MAY have to use the method I described above for a pinned gas block.

    I doubt DPMS dimples these barrels, as it is their budget line and it would add quite a bit of time to the machining process. Not knocking the rifle or the company. There is nothing wrong with them. But they do omit a few steps that may be desirable for those willing to spend more $.

    They probably don't pay much attention to squaring the as block to the upper as they bill this model as an 'optics ready' carbine and probably expect most people to slap on optic on it.
     
    Last edited: Mar 19, 2019
  11. 340PD

    340PD Member

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    Good stuff.
     
  12. dubya450

    dubya450 Member

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    No, he's not...

    He will have to invest a little more money but a simple clamp on lo-pro gas block and a more modern style free float mlok or quad rail is all it takes, an upgrade many folks do anyway. Pinned gas blocks aren't difficult to remove either.

    I had a Colt 6933 upper that had a FSB so badly canted that I couldn't get it on an 8x11" target at 50 yards. I was still able to install a lo-pro block under a free float Midwest Industries rail with plenty of clearance.
     
  13. Coal Dragger

    Coal Dragger member

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    My comment was that in his rifles current configuration if the gas block is pinned or set screw/dimpled he is in fact SOL.

    Of course throwing new parts at it can solve the issue. If he doesn't want or cannot afford to throw new parts at it he is SOL.

    The most obvious solution to this problem is to call DPMS and tell them they have a defective product and they need to fix it.
     
  14. DoubleMag

    DoubleMag Member

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    This ^^ here. Contact the manufacturer if it's not an easy kitchen table fix

    It's a new rifle, DPMS' error. They proof shoot the guns several rounds & out the door. It happens. IMHO they should even issue a ship label
     
  15. IndianaBoy

    IndianaBoy Member

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    James, any updates? Curious if you had a chance to look at your gas block.
     
  16. IndianaBoy

    IndianaBoy Member

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    Bump.


    Curious if James was able to sort out his issue.
     
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