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Barrel Installation AR-15

Discussion in 'Gunsmithing and Repairs' started by D51208, Jan 19, 2012.

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  1. D51208

    D51208 Member

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    Hi All,

    I am looking at doing my first AR-15 build. Stripped lower, semi Stripped Upper (forward assist and dust flap installed). I am pretty familiar with the rifle overall. I am trying to pinch pennies where i can for now. My main question that really has me questioning life right now is the barrel installation. Do you need to head space check it?

    I have been seeing all over the internet and on videos that people just stick the barrels on and assmble the gun, no headspace and supposedly fire it. The whole head space game is new to me. I have read that without a machine shop or changing bolts that there really is no way of changing head-space on AR-15's? So should i not bother buying any headspace tools for now? Is there a way of checking head space without those tools?

    If it all possible i would like to get away building this rifle with the bare necessities, the parts, some lube, some loctite, and the armorers wrench.

    Any knowledge or wisdom is welcome, along with any advice or recommendations.

    I am looking at building a standard milspec firearm with an 18" barrel, rifle length gas system.
     
  2. rcmodel

    rcmodel Member in memoriam

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    That is true.

    But on a new build with a new bolt, new barrel, and new barrel extension?

    You are at the mercy of the gods that all the tolerances on the three new parts don't stack up the wrong way and give you excess headspace.

    Get at least a Go gage.
    You can use four layers of Scotch Magic Tape (.006") on the GO gage " for the NO GO gage.

    rc
     
  3. Mac's Precision

    Mac's Precision Member

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    This is what I do. I don't own a lot of NO GO gauges. I have some but only in calibers I do a lot of work on.

    Rc Says:

    Get at least a Go gage.
    You can use four layers of Scotch Magic Tape (.006") on the GO gage " for the NO GO gage.
     
  4. D51208

    D51208 Member

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    I thought the go gauge was the one that wont let the bolt close and lock all the way?

    The more i look into this the more i get confused.

    Couldnt i just check to see if a bullet will chamber correctly by chambering a bullet and observing, removing the bullet and use the guage that isnt supposed to shut? Could i magic tape the bullet to replicate that gauge to save money?
     
  5. Livnoutdoorsxd9

    Livnoutdoorsxd9 Member

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    Why don't you just buy a bbl and bolt from the same mfg? Any company worth a damn will check headspace for you and ship them out together. You're over thinking it.
     
  6. griff383

    griff383 Member

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    Livnoutdoorsxd9 makes a great point, but if you are compelled to order them seperate you can ask whoever you buy your barrel from to headspace your bolt to the barrel. Just send it in and they will headspace for you.
     
  7. MtnCreek

    MtnCreek Member

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    I asked my smith about this a while back. He said he checks headspace on every rifle he builds because as a smith, he would be reckless not to. He also said he has yet to run across a new ar barrel / bolt that didn't check OK.

    I suggest buying or borrowing a high quality wrenchand upper receiver block.
     
  8. rcmodel

    rcmodel Member in memoriam

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    No.
    It is called a GO gage because it will Go in and the bolt will lock.

    A NO GO gage is called that because it will not let the bolt lock if the headspace is correct.
    In otherwords, it is a NO GO trying to chamber it.

    You ask about using a loaded round for a gage?
    Again, there are min/max manufacturing tolerances allowed in all ammunition.
    SO how do you know the round you pick to use as a headspace gage is right?

    rc
     
  9. Mac's Precision

    Mac's Precision Member

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    The only time I use a cartridge as a chamber gauge is when I am building a custom gun for a man that loads his own ammo. In that circumstance we already have the dies he is going to use, selected the brass he is going to use, had him size his brass WITH the dies he intends to use, done case prep as he will with live rounds and had a reamer made to accommodate a match grade chamber and also use a custom throater to address a custom bullet seating depth.

    In that case Pacifc Tool and Gauge will make a reamer that is going to be tighter than SAAMI spec. In the end it will be a custom chamber that requires a specific manner of handling brass. In that case I will do the no go tape trick on the case head. This type of special circumstances is unique to a tack driver custom gun for a special customer.

    In the case of the AR, the chambers are going to be large to handle dirt, and variances in ammo manufacturing. You will have some tolerance with head space and a little bit is not the end of the world. All guns have it with exception of customs like I described above. I'd say you have a very strong chance that your set will work fine. I'd get a go gauge and tape it. Make sure you are safe and get on with life.
     
  10. rbernie
    • Contributing Member

    rbernie Member

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    When you buy an over-the-counter AR-15 barrel, it will have a barrel extension already installed and properly headspaced (presumably to some midrange value within the spec, but not to the specific bolt you will be using).

    You can, out of an overabundance of caution, check the completed rifle's headspace. Alternatively, you can do what most do and simply assemble the rifle from reputable parts and trust that the parts tolerances all fall within a range that yields acceptable headspace.

    Exactly so.
     
  11. Strykervet

    Strykervet member

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    Knew an SF gunsmith. He mostly worked on M4's, didn't use a guage didn't use a torque wrench. He taught me how to do it, how to feel for it and I don't either.

    It is one of the few weapons I would do this with, and I'd be sure to get good parts. Milspec minimum. If at all possible, get the bolt and barrel together.

    I wouldn't try doing this with Oly parts, that is for sure.

    Oh yeah, get the vice and vice block or just get one already built --you can't really do it without that. You can, and I have in a pinch, but it isn't something I'd recommend AT ALL. In another pinch, I tried to get it apart without my blocks and I trashed the upper (but I kind of expected it and didn't really care, I just wanted to salvage the barrel). You really aren't saving much by doing it yourself if you have to buy the block and don't plan on more builds. I have the stuff because I build all my own and when using very high end parts it IS a lot cheaper to DIY.

    Without the proper education or being around someone that did this forever (that SF gunsmith? he was an armorer in the navy for nearly 30yrs first) I would be careful. My first build, before I knew this gunsmith, was using the military armorers TM for the M16. You NEED that if you are new to this. Only a few bucks, priceless info for someone new to building AR's.
     
    Last edited: Jan 26, 2012
  12. D51208

    D51208 Member

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    Thanks for the Information guys. I'm just waiting on getting the new barrel in. I have the M16 TM book. (My brother found it for free for an app on his ipad thing). I have an Armorers wrench. I plan on building a makeshift upper vise block out of a bunch of wood I have.

    So my plan is to get a GO gauge and tape it. I just want to get all of my info correct first before i go ahead and do it.

    Go gauge, go's in and locks. Im good.
    Go gauge taped to a no go, does not go in and lock. good to go. Anything other than this bad.

    My question is where do I tape the gauge? Whatever tape I use must make the area I put it on .024" thicker right? Could you post a pic RC?

    Again, I appreciate the Info guys.


    BTW I totally would go with someone who made both the barrel and bcg. Buuut I got a kickass deal on a brand new M16 BCG.
     
  13. D51208

    D51208 Member

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