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I don't get head spacing and parts.


Powerman

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So I "get" what head space is, but don't understand what you do about it. I'm building my first AR, and trying to find parts. But it seems to me... you just assemble your parts, and then check go-no go. If it's no go then you toss those in the trash and try another one.

How do you go about buying parts to put together, and how do you get the correct head space with all these parts?

How do you change different barrels or buy new bolts in the future?

Thanks.

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On the AR it's pretty simple, buy from a reputable manufacturer and ask for a matched bolt. They will headspace it for you. Headspacing is usually done when a barrel is assembled anyways, if you ever get one that doesn't headspace correctly, you should check that your bolt type is correct, and after that you need to send your barrel back to the manufacturer.

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Ya, you will need to slow that down for the AR impaired.... :)

I saw Shilen has matched barrel and bolts for .223, but not .308. But then just buying "parts"... I do not see any other "matched" parts. And no "specs" to match anything to head space wise. Of course, these days there is no parts at all, but between carriers, bolts, and barrels, nothing is matched. Most people seem to have not problem mixing and matching, obviously with what fits.

So how do I go about getting parts to assemble?

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Headspace isn't something you'll assemble, or worry about getting right, on your end.  The barrel manufacturer has to get that right, when they build the barrel.

You have a couple options - buy headspace gauges and check the headspace - if it's not right, you'll need a good AR gunsmith to get it right for you.  Usually involves reaming the chamber.

Buy a bolt that's already been headspaced to your barrel.  Most of the time, this is a service that those selling barrels will provide for you.  Research which ones will do this, and make your barrel purchase from them.  Hint: Rainier Arms and Fulton Armory are two that will do this.

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The real bottom line is it's a verification process for your safety. When you are buying from a supplier who offers matched sets they are usually not fitting anything. They are merely trying two parts off the shelf. If it passes the tests it's shipped. If it fails they simply try more parts from stock. Now if you order a custom barrel you should provide the bolt so they have it in hand when they fabricate your barrel. That's ideal. Places like Fulton Armory and Rainier Arms will verify a bolt you buy from them or your own bolt to one of their barrels.

We see to many strange tolerance issues in these large rifles. I believe you cant be too careful. The 308 Winchester cartridge has a lot more energy than a 5.56 and I feel it warrants a little more attention from the DIY'er

FWIW I feel you should check any used rifle you buy too.

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OK, thanks a bunch guys... I see what you are getting at. I have seen plenty of folks that will take your bolt and test.

I think I have narrowed it down that I'm getting a Fulton barrel (before you guys mentioned this). They have carriers, but no bolts. It would probably be wise just to order a barrel and bolt and just wait for it to come in when ever that will be.

Fulton still has some parts, but no telling when they will have more. I am willing to wait for a whole Armalite upper... but they have NOTHING on their site, so no clue how long that will take. I'm not in any particular hurry, but obviously I would like to shoot it this Summer.

I might have a line on a BCG... we'll see. If that happened then I could send it to Fulton for a barrel. Does that sound right?

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.308 or 5.56, brother - we have to ask.  Need to know what we're fully working with here, because the answers are going to be very different.

I'll make the ass-umption that it's a .308, due to the section it's posted in - you're not going to fit an Armalite upper on a DPMS lower.  You'll need to search out some DPMS-compatible parts, upper being one of those.  Fulton Armory exclusively uses DPMS-based parts in their semi-auto .308 choices, so you're on the right track with them.

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.308 DPMS, striped. Armalite buffer assembly, DPMS LPK.

I understand lowers are different, but I thought Armalite uppers fit DPMS lowers. And RRAs uppers do not. Armalite does not have anything anyway. It's down to waiting on back ordered DPMS stuff. I talked to DPMS the other day and they are telling everyone 12 months at this point.

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Pick up a stripped flat top upper from Fulton Armory, and you'll be much further ahead, anyway.  When it comes into stock, grab one quick.  Get a DPMS-compatible rail system of choice, combine those parts with your Fulton barrel, and you'll end up very pleased.

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Thanks. It was looking like that was going to be the call I place tomorrow.

So it seems BCG are hard to come by. I assume they work fine with DPMS/Fulton uppers as the info on this site says. Are they pretty good about production, or are they always behind. Obviously, right now everyone is cleaned out... but I do not know how the .308 market was to begin with. I have just always wanted one and decided I better get off the pot.

what is my best best for a Bolt.... JP, get a Fulton carrier and wait for any bolt?

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