AR-15 Headspace Question

I am about to assemble an AR-15 upper. This will be my first time, so I have done some internet searching and “opinions” on AR-15 headspace seem to range from “who cares”, to “you’ll put an eye out, or the barrel will blow up in your hand” if you have not checked the headspace on your upper build.

I have a Trybe .223 Wylde barrel. Don’t know who makes it, but Trybe appears to be made “exclusively” for OpticsPlanet. Regardless, I’m the kind of person that isn’t afraid to ask stupid questions and display my lack of knowledge on a subject. It would appear to me the headspace on the AR is completely a function of the chamber dimensions of each individual barrel. The reason I say that is the BCG will be pressed into the rear of the barrel until lockup. Am I wrong?

Do I really need to order 5.56mm Go, No-Go headspace checkers to check one barrel to assemble one AR-15 upper assembly? I know the answer is “it won’t hurt”, but I am tired of storing single use tools if they are not necessary.

As a follow-up, if there is a headspace issue, how do you resolve it? Return the barrel to OpticsPlanet for rework or replacement?

I am going to tag @Craig6 and @Harvey because I’m sure both of them have background on this, but anyone has input, please help me out, Thank you!

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Have it installed by a gunsmith. Done. No worries

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I second this.

We don’t even check headspace & timing on M2s, anymore. (I still can’t get used to that.) But anytime you’re attempting to do more than user-level maintenance & cleaning to a firearm and you don’t feel comfortable, take it to a qualified smith. It’s cheaper to take it before you screw up your firearm.

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What about M4 and M16?

I’ve resorted to taking 2 guns to “experts” to have them fixed. I ended up having to fix both of them myself. The 1st one is a family heirloom I didn’t want to risk screwing up working on myself. A local gunsmith worked on my gun for a week. He called me and suggested I take it to another gunsmith to see if someone else could figure it out. Since the gunsmith was not successful in the repair, I took it apart, evaluated it and fixed it myself. The 2nd experience was with a brand new Springfield 1911. I sent it back to Springfield for warrantee repair. They returned it with the same issues. You guessed it, I had to take it apart and fixed it myself. What I’m saying is I have not had good luck with gunsmiths so far :grinning:

Besides, I enjoy learning new things.

@Gary_H Let not your heart be troubled. When you buy a AR barrel it is assembled to the correct head space for a standard AR bolt head. The barrel of an AR is just like the barrel for a Remington or Winchester bolt gun. The difference is the barrel collar. The barrel and the collar have only so many threads and they are “headspaced” via what I call the Remington Headspace Methodology which roughly means they torque the collar on until it headspaces correctly THEN they drill the gas hole in the barrel on a jig so that the locating pin is correctly aligned to your upper. Pin down gas port up. The space inside the barrel collar is calculated to receive the bolt head.

Now anybody with any machining knowledge at all knows that variances can “stack”, to fix that the designer of the system “Mr. E. Stoner” ensured that the last several thousandths of bolt travel when the bolt rotates into the “locked” position can be variable. Basically the bolt pushes the round into the chamber until the shoulder hits and then stops. It’s not hard against the bolt carrier but it kind of “floats” between all the way forward and before it starts to unlock. H&K uses a similar notion on their MP-5 series of guns and G-3 series and they advertise it as a “floating bolt head”. If the round is too far out of battery the locking lugs wont rotate into place and the hammer will hit the bolt carrier not the firing pin, which is also floating. The inertia of the bolt going forward keeps the firing pin forward and the last bit has to be provided by the hammer hitting the nub that is exposed.

If you look at the back of the bolt lugs on an AR that has been fired a lot there is NO wear on the back of the bolt lugs so they don’t actually “lock” into the barrel collar they just rotate into that position and then rotate back out unlike a bolt rifle where you can hand lap a sticky bolt to smooth it up. I know guys that barrel their own AR tubes to the collars and they go all out for the precision head spacing, most have given up doing it except on the AR-10 platforms with exotic cartridges as it is just not worth the effort and just about every barrel MFGR out there will spin you a tube and set it for what ever AR platform you have.

A note on “Certified Gunsmiths” or “Gunsmiths” in general. There is no sanctioning body that grants a license to be a gunsmith. There are some schools (college / trade schools) that will teach you how to work on guns but only the ones in their curriculum. Most Gunsmiths are guys that know how to “figure it out” some specialize in certain platforms or brands and they get very good at what they do. Most “Gunsmiths” you find out there residing in a gun shop are guys that have a mechanical knack and have replaced a lot of parts without screwing up the finish.




@Ouade5 Do you mean you are not “allowed” or that they no longer teach timing and headspace on Ma’ Duce? The latter part would freak me out. Ma’ Duce can be a finicky wench if she is out of time and when you need her you’d best make her happy.



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There’s an updated model that no longer requires headspace and timing when the barrel is changed. It’s very uncomfortable for those who were taught to be diligent with H&T or risk blowing up the gun. :smile: