I was thinking about building my own upper, but was strongly advised by the MFG tech support unless I had a what he called a special "Jig" that has "Spines" that looks like a bolt carrier, but what that allows is to achieve proper alignment and torque of the barrel nut.

He said if you were to build this using the conventional means, "home methods" that there is a chance I may or may not get the indexing right on the first try, and that you can only loosen and re-tighten the threads on the receiver before they become basically no good.

I am now scared to try and build an upper because it seems too hard. Is what he is saying about loosening and re-tightening the barrel nut will ruin the threads? He said maximum 2x maybe 4x most.

What I learned in my three builds as a beginner.
The barrel has an extension ring that is attached precisely to establish the correct head spacing. This extension also has an indexing nib that aligns into the indexing slot on the upper. Most barrels come with the extension attached and adjusted, if not, you will need the proper tools and knowledge to attach it. This is where major problems arise in attempts by first time builders. Incorrect head spacing is usually catastrophic in any firearm. Make sure your barrel has the extension ring attached when you buy it.

Research,tools and patience. No shortcuts in any of these,run the build thru your head over and over before you put any part together. The research should also reveal that quality parts are central to avoiding issues such threads,tolerances etc..mixing milspec with non can certainly create problems for a beginner. Tools are definitely a must and not overly expensive.
Once you start,go slow,dry fit,check then check again. Since aluminum comes into play with many parts, I guess it would be possible to wear out a thread but if your research in parts and procedures was thorough, they shouldn't wear out in just a few attempts at assembly unless excessive force or impatience is present.

I found the bolt carrier group assembly to be more intricate and complex than the barrel and gas assembly.
Go for it, it's not hard at all once you complete one. Just think it thru,dont rusk and be certain of your parts compatibility and quality. I'm sure some with alot more experience and knowledge will be along to advise. I am happy with the reults my projects and found the last one was exceptionally easy and straight forward having done the previous two. Good Luck

I believe what's being talked about is the indexing of the barrel nut so the gas tube hole/notch lined up with the hole in the upper receiver for the gas tube to pass through.

Sometimes it's tricky to get the nut cinched down and have the hole line up right from the start... usually you need to make a judgement call and decide whether to crank the barrel nut down a tad bit more or back it off, to get the alignment.

Putting together an upper is not rocket science... remember, one of the purposes of the modular design of the AR was ease of assembly and repair, in a less sophisticated settings than a gunsmith's work bench with all of the attending precision tools and gauges.

One doesn't just slap one together in a few minutes (although some people I know have become so proficient that it seems like they do), but there is also no reason to get all OCD over it and over think the process either... unless you're talking about a precision match rifle.

Don't be intimidated... give it a try, take your time first time out, have some fun with it. I've built 4 AR's... you learn and improve, and you can always go back and fine tune what you did on the first build.

Also, all uppers are not created equal... quality and price points vary. That thread life stated, in my opinion has been overly generalized. Receivers machined from solid billet verses investment cast will stand up better.

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Conrad
SWCA #1830 SWHF #222

Get a Gibbz Arms Forward Handguard, they feature a design that doesn't require any fooling around with a spline nut because they don't use a spline nut. What you do is screw the mounting adapter for the handguard to the upper with a bit of locktite blue, make sure that adapter is perfectly aligned with the upper, and finger tighten the internal nut and wait 24 hours till the locktite has set. Then you use a 1 3/16 crowfoot and torque wrench to torque that internal nut to 40 ft.lbs. After that you mount the handguard and you are done. Note, in the event you have to break loose that adapter to mount a new barrel once you have the internut unscrewed you will need to heat the mounting adapter to about 150 degrees (a large pot of boiling water to "steam" the junction will work well) and you should then be able to break the locktite loose.

Final note, the Gibbs Arms handguard range between about 120 and 190 bucks so they are not cheap but they do come with everything needed except the crowfoot or torque wrench. For the crowfoot go to pts-tools.com, they sell a 1 3/16 crowfoot for something around 22 dollars, actually they have a snap on for well over 100 bucks and an "import" for about 22 bucks. I have the "import" and IMO it's the exact same part as the Snap On except it isn't stamped Snap On, it's unmarked.

Finally I have found the Gibbz system so easy to use I now have 3 AR's with their handguards and a co-worker who got me into building AR's has now put the Gibbz handguards on two of his builds. They aren't cheap and are sometimes out of stock in some lengths but they are an EXCELLENT design.

This is correct. ^^^
As a competitive Service Rifle shooter, I change my barrel out about every 2,700-3,000 rounds, which is at least once a year for me. One of my uppers has had about 7 or 8 barrels on it and I expect to keep on replacing the barrels on it for the foreseeable future.
Indexing the gas tube isn't that difficult either. Crank the barrel nut down to near the proper torque and then check to see if the gas tube will line up. If it doesn't line up just perfectly, either crank a bit tighter or loosen it up a bit until it does. That's really all there is to it.
I highly recommend the two following tools for doing the job:
PRI Barrel Nut Wrench AR-15
Geissele Reaction Rod AR-15 Vise Block Steel

+100 on the Geissele tool noted above.

This is pretty much it.

In some cases, you may have just a bit of play between the indexing pin on the barrel extension and the upper receiver, and this can result in the front sight in a pinned gas block assembly being very slightly off the vertical relative to the rear sight.

However, it has to be way off before it becomes an issue that precludes properly zeroing the rifle in windage and elevation.

If you've got a barrel that does not yet have the holes for the gas block pins reamed, it's a total non issue as you can level the gas block and front sight with the upper receiver before you ream the holes.

The same thing applies if you've got a gas block that clamps onto the barrel.

The last few times I've changed barrels on my service rifle AR-15, I've used a Compass Lake barrel that has four flats on the barrel designed to engage allen screws in the front sight base/gas block that allow you to true up the front sight. It's pretty idiot proof.

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I've done numerous AR-15 builds and I've only encountered one where a tooth on the barrel nut, when properly torqued, aligned with hole for the gas tube in a manner that caused a problem.

In that case, backing it off for clearance allowed the barrel to rotate slightly, and tightening it up enough to clear resulted in what I felt was excessive torque. The issue was some out of spec parts, but the quick and dirty solution until I got a proper barrel nut was to just Dremmel off the offending tooth and go with the proper torque value.

Shimming is another option in that situation, a better one if you do not want to replace the offending part, and if you have the proper tooling, you can also lap and square the face of the upper receiver - but that's pretty advanced stuff and does start to mess with the design dimensions, which can cause as many issues as it solves.

But...buy quality parts and it will not be an issue.

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Putting a barrel on an AR-15 is a lot easier than re-barreling an FAL where you have to take much more care in timing the barrel to the receiver - and in some cases will have to stipple, shim or turn a surface to get the proper torque, and it's a lot easier than working with an AK where you have to press the barrel into a trunnion while ensuring it is properly timed.

That's not the case. I've got a half dozen barrel changes on my Service Rifle AR-15 and there's no reason it can't go a dozen more.

You do want to at least lightly lubricate the threads, to reduce the potential for galling the aluminum and keep the anodizing intact on the receiver and the 30 to 80 ft pound torque values are based on lightly lubricated as opposed to dry threads.

Here are the torque specs that matter:
Compensator (Flash hider) 15-20 Ft. Lbs.
Barrel Nut - 30 Ft. lbs. Minimum, not to exceed 80 Ft. Lbs. to align the next slot in the barrel nut.
Carrier Key Screws - 35-40 INCH pounds.
Lower Receiver Extension (Buffer Tube)
Rifle: 35-39 Ft. Lbs.
Carbine: Tighten the castle nut to 40 INCH pounds +/- 2 inch pounds.

Bear in mind when torquing the barrel nut that the barrel nut wreck is in effect a crows foot, and the offset on it will affect the torque value. It's not a big issue unless you are close to the upper or lower limits.

Figuring torque with a crows foot wrench

Headspace should not be an issue with barrel extension and bolt that are within specification, but you do want to check it:

Head space information FOR 5.56
New barrel Headspace: GO gauge 1.4636
NO GO guage 1.4696
Field/Unsafe barrel Headspace: 1.4730-1.4736"

I bought the Magpul AR wrench and the Magpul vise block, I've tried others and just gave them away after using the Magpul tools. Getting the barrel indexed and torqued isn't the hard part it's like said before, when you have to ream the holes if you are using a F style front sight base, you have to align the sight with the barrel and center everything, or you may not have enough rear windage adjustment to be in spec. If you are using a after market forearm and a different buis or a scope, than all you have to do is come close centering the gas block.

Listed below are two good AR15 assembly books available from Midway USA and other sources. I am also a service rifle shooter. I change out a barrel every nine to twelve months. It is not that hard to do. Only a few simple tools are needed.

"The Competitive AR15 Builders Guide" Book By Glen D. Zediker $32.99
"The AR-15 Complete Assembly Guide, Volume 2" Book by Walt Kuleck with Clint McKee $19.99

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DRB #2276

Zediker's books are fun to read, at least to me.

Which float tubes are you service rifle shooters using? I'm trying to decide between White Oak and Compass Lake for an optics service rifle upper I'm building.

Thanks
Lou

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NRA Certified Instructor & RSO

I use a White Oak on my rifle.

Bushmaster used to sell an excellent video that showed how to properly build an AR to the same standards they put them together - very specific instructions given, such as "exactly a guarter-turn past. . . ."

I have no idea if they still sell it now that Bushmaster is owned by Remington.

That said, this is one of those things that "if you have to ask. . . ."

Do you need to use loctite on the threads? I've read the instructions online and I believe White Oak uses a lock nut arrangement that requires loctite. I'm concerned with disassembly to change out barrels if I use the White Oak tube with loctite.

Lou

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NRA Certified Instructor & RSO

I've never had any trouble getting my White Oak tubes loose. I use blue Loctite when I put it back together.