how to align your gasblock

Discussion in 'AR-15 Discussion' started by JonM, Jun 23, 2014.

  1. JonM

    JonM Moderator

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    question that pops up from time to time is, my rifle isnt cycling properly or how do i get my gas block square.

    well there are a couple ways one involves eyeballing it with ye olde mark 1 eyeball. this can work and it can be a lot of fiddling to get right.

    however i prefer to do it right the first time and know its going to be allowing the gas to flow into the block with no issues.

    here is how i do it.

    tie some thread to the barrel extension stretch it square across the index pin so its centered. then bring it down the barrel centering over the gas port. make an index mark on the thread and barrel.

    [​IMG]

    next tie the thread to the block align along the center of the gas tube hole make second reference mark.

    [​IMG]

    now you can easily align the two marks tighten the set screws then check the marks for movement and readjust if needed.

    [​IMG]

    while it looks a little off in the three pics thats just my crappy photography and camera perspective. but they give you the idea
     
  2. fa35jsf

    fa35jsf New Member

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    Wow this is great info. You should sticky this in the AR-15 threads
     

  3. Quentin

    Quentin New Member

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    Nice 'n' Easy! I like!
     
  4. dwmiller

    dwmiller Well-Known Member Supporter

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    Nice and simple. Much better then the laser level and machined bracket that I've been using for the last few years! Thanks for the info JonM!

    +1 on the sticky, maybe a new topic "AR Build Tips and Tricks" Start collecting some of these build tips in one place...
     
    Last edited: Jun 24, 2014
  5. JonM

    JonM Moderator

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    Thanks. I got the idea from law and order criminal intent a few years back. One guy was being framed for murder by his wife who had done a murder for hire and the hitman used a steel wire to strangle a victim. The wife planted a modified chalk snap line her husband always carried replacing the line with wire so he would get busted going through the court metal detector.

    I was swapping out a bent gas tube and cleaning my carbine while it was on and thinking about gasblocks and how to align them...

    Stupid, but you never know when an idea hits

    I will leave the condensing to someone else who is less apt to erase subforums...
     
  6. okdonk

    okdonk New Member

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    Nice info, thank you!. I just properly aligned and installed the gas tube last night by marking with pencil and a paper name card. Also dimpled the barrel right where the gas block screws sit tight.
    Google and Youtube are free knowledge.
     
  7. gunny91

    gunny91 New Member

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    Awesome idea ill keep it in mind thanks JohM
     
  8. BulloftheWoods

    BulloftheWoods New Member

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    I have a question for the at experienced. I'm buildind an ar10 and I'm fixing to buy my gas block. Been looking at a lot of different designs out there. Was wondering which one if it even matters is better. The ones that clamp to the barrel or the set screw type. Thanks for your consideration.
     
  9. JonM

    JonM Moderator

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    Set screws work better. They are less likely to slip from abuse than clamp on.

    Use a bit of rocksett on your set screws. Do not put anything on the barrel surfaces or inside the gasblock like locktite. I clean the surfaces with acetone to remove grease and oil Asyou want a clean fit.
     
  10. Sniper03

    Sniper03 Supporting Member Supporter

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    JonM

    Great information on the tread technique! I will try it! Thanks
    I will Share another option.

    I use a bubble level and a large paper clip.
    1. I put the pivot pin lug in my vise to hold the upper receiver and assure it is level,
    2. I put a small "L" Bend on the end of the *Large Paperclip and straighten out the rest of it.
    3. I put the Gas Block on the Barrel loose.
    4. Insert the "L" of the Large Paperclip through the Gas Tube hole on the Gas Block and into the Gas Port Hole then tape the long straightened part of the paperclip to the barrel. This keeps the Gas Block from cutting off part of the Gas Port Hole while finishing the installation.
    5. Slightly snug the screws on the Gas Block. But loose enough I can move it on the barrel to level it.
    6. Level the Gas Block with the Flat Top Receiver (And Quad Rail if it is included in the assembly!)
    7. Put three location marks on the barrel and the gas block with a pencil or silver marker. The first being right under the Gas Block Opening and on the Barrel & Gas Block. And then one at 3 and 9 o'clock on the Gas Block & Barrel. These three marks show you the location on the Gas Block position on the Barrel when reinstalled with the Gas Tube in it for final assembly. Then you can remove the Paperclip at that time.
    10. When ready for final installation I recheck the level of the Receiver and Gas Block when tightening. (And Level of the Quad Rail if used!) All will be on the same level.
    11. After tightening the screws if they are the type that screws into the barrel. I then remove one of them and put a little Blue Thread Locker on the screw and reinsert that screw. Then remove the second one and repeat the Thread Locker. If you have any doubt about the security of the screw and barrel contact type you can also take a small punch and put slight indentations in the barrel for the screws to fasten more securely.
    Or use a small drill press and while having the screws removed for the following Thread Locker application you can take a diamond tip drill and put a slight indent in the barrel for the screws to fasten more securely. But most of the time the final step is not required. With the clamp on Gas Blocks this final step is not applicable.
    The above procedure allows you not only to align the Gas Block but also assures the right location on the barrel so it does not cut off any portion of the Gas Port. When installing a Gas Block on the M-4 Style Barrel, DO not forget that when removing the End Cap that holds the traditional M-4 hand guards that the End Cap takes up space. Using some Gas Blocks if you push the Gas Block all the way back against the shoulder on the M-4 Barrel the Gas Port can possibly be cut off! I believe Yankee Hill is making gas blocks now to allow for this issue by making the gas port hole in the gas blocks slightly oversized.

    03
    Here is the Level I use!
     

    Attached Files:

    Last edited: Feb 15, 2015
  11. clr8ter

    clr8ter New Member

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    Interesting stuff. How is the gas tube secured into the gas block and receiver? Is it a snug slip fit?
     
  12. okdonk

    okdonk New Member

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    The gas tube end which goes into the gas block is secured with a small pin. Very rare and i never heard it will go wrong once you pinned it right.
    The other end of the gas tube will slide into the receiver, not tight but it can wiggle lil bit.
     
  13. clr8ter

    clr8ter New Member

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    Interesting. Wouldn't it be cool if the manufacturers could get together and come up with a standard for making a shallow indentation in the barrel at a certain point, and then have a set screw or pin protruding from the gas block that aligned it and kept it from moving? That'd make it REAL easy. It would also make the clamp on one work better by keeping it from moving around.
     
  14. okdonk

    okdonk New Member

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    More manufacturers started to dimple their barrels so that the gas block set screws will stay in place. Of course you need to put a lil drop of loctite too.
    BCM is one of the first manufacturers which i noticed of dimpling their barrels for gas block set screw.
     
  15. clr8ter

    clr8ter New Member

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    So, can that actually be used as an alignment tool, too?
     
  16. okdonk

    okdonk New Member

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    I won't rely on it as an alignment tool. I will still do as JonM and Sniper03 mentioned for an extra peace of mind.
    Do it once in a proper way then you won't have to worry anything else.
     
  17. BulloftheWoods

    BulloftheWoods New Member

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    Hey Mr Jon and Mr sniper03 thank you for sharing your experience. It sounds very solid and now I feel I can go forward with confidence. Its the set screw type for me, with this great help its gonna be straight for sure. Thanks guys.
     
  18. JonM

    JonM Moderator

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    There is no standard for gasblock dimples as the gasblock is not a standardized part. You will be forced to use a gasblock that fits the pattern used. When i replaced the fsb on my bcm with a lopro gasblock in order to use a fftube aligning it increased the ammount of gas flow over what it had before.

    I knew this by the ejection pattern changing.

    i prefer not dimpling the barrel as a slight misdrill can easily change the orientation of the block. drillbit chatter is a real issue on a round hardened steel barrel. You have to have a proper jig and drill press to drill the dimples correctly.
     
  19. timothyj999

    timothyj999 New Member

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    Here's how I do it: I put the gas block and gas tube in place, close to final position. Then I take a 2-foot piece of 1/8" ID aquarium tubing and slip it over the gas tube in the receiver (wet it to make it slide on easier); the other end goes in my mouth.

    Start blowing through the tube and when the holes in the block and barrel start to align you'll feel and hear your breath escaping into the barrel. The amount of air escaping is proportional to the alignment of the holes.

    Thing is, it's *very* easy to tell when the holes are exactly aligned--the effort you're using to blow through the tube suddenly gets much less when the holes line up. If you have an assistant, you can have them tighten the set screws while you keep puffing air, and you'll be able to tell if the block has slipped.

    Works like a charm.


    Sent from my iPhone using Firearms Talk
     
  20. McX358

    McX358 New Member

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    Sometimes "Locktite" can be a wonderful thing; just remember to use the right one for the correct application.