Squaring up an AR-15 upper

[Dolomite_supafly]

I posted this in another post and thought I would make its own thread.

I generally do because the "flat" surface that the barrel mounts to is generally off by several thousandths. And think about it, being off by .001 equates to .1 off at 100 yards and creates additional harmonics when the surface isn't flat. This ensures the barrel is inline with the upper and mated squarely.

Almost every custom bolt action builder squares the front of the receiver as well as the recoil lug. The same should be done to accurize a AR because they are rarely square. Squaring it puts the barrel inline with the receiver and hopefully settles down any additional harmonics.

Here are pictures of one I did for myself:

First I start out with a round tube that is cut to allow for a very tight fit into the receiver where the barrel goes. And I clearance it to allow my cutter to get a full width cut. I make sure to cut a new tube each time to make sure it is true.

Next I start to surface the front portion:

You can see where the imperfection starts to to be cut at the 12 o'clock position. And because this is the high spot it tilts the barrel down and you loose up on your scope, something important for those shooting longer ranges where every click counts. This is normal for the high area to be here first.

This is about 1/2 way there and now the high spot is on the left of the receiver, pushing the barrel to the right:

And finally all cleaned up:

And the reason I do this is because when the gun fires the barrel shifts back against the receiver where it is supposed to be a flat. And in this case the first void is everything except at 12 o'clock forcing the barrel down and creating additional harmonics. Then is settles into the right side of the receiver because the left side has a high spot and again more harmonics. And it is all these varying harmonic frequencies that can cause a gun to seemingly never be accurate.

After doing this the barrel doesn't shift or squirm around upon firing or at least not as much, it comes straight back squarely on the receiver. This reduces the harmonics to only what is inherently in the barrel.

And this receiver had been properly torqued but still had high spots.

And the 20 minutes to do this put me in bed for the rest of the day. Damn I hate my back.

Questions are welcome.

Dolomite

[Guest 6.8 AR]

That makes sense to me, Dolomite. I never thought about doing that. Great post. Thanks

[CQB Elite]

Great post! I only have 1 question- will you do this to the upper on my build? Just kidding!

I'm building an AR using a Noveske stripped upper/lower set. I've been looking for a barrel and won't be long till I'm ready to put one on. There's no way I have the technical expertise to do this to my receiver but it was an interesting read!

[dkd83]

Do you find this on all ARs? I am finally going to buy one and wonder if this is something I wiil need?

[JeffsSig]

Now this is the kind of info and post that should be found on gun forums.

Thanks Dolomite

[Dolomite_supafly]

Every forged upper I have looked at is like this. I will say I haven't looked at hundreds or even dozens but every one is like this. And just so you know the one in the picture above is a upper with the keyhole forge mark which is the same for probably 75% of the AR's on the market, including some high end guns.

This is the one case in which billet is probably better although I have never checked a billet.

I use a 1" OD tube then turn it down for the receiver hole which, if I remember correctly, is .995" ID. So I basically skim the tube and press the upper in place. The friction holds it in place enough to make a few SMALL passes. Make sure the tube goes all the way into the receiver.

And for the average person this would not a concern and wouldn't warrant the time, effort or money to do. But for those who want to squeeze every possible ounce of accuracy out of their AR this could help.

And just so everyone knows this was my dedicated 22lr AR. I did it because I had the gun apart and figured it wouldn't hurt. It also gave me a chance to take some pictures for others to see.

Dolomite

[Guest 6.8 AR]

I'm going to take my Ranier Arms billet upper apart just to see if that's the case with it. I know it has the tightest

fit of all mine, but that's not what you have described. I believe it to be the case with all the keyhole uppers,

though. The dimensions of those are workable, but they vary quite a bit from one to the next. I never thought

about it being a big deal until now.

EB-SF, you're not thinking about a Noveske barrel? Got a good start on a complete Noveske gun, piece by piece.

Might as well.

[CQB Elite]

I'm going to take my Ranier Arms billet upper apart just to see if that's the case with it. I know it has the tightest

fit of all mine, but that's not what you have described. I believe it to be the case with all the keyhole uppers,

though. The dimensions of those are workable, but they vary quite a bit from one to the next. I never thought

about it being a big deal until now.

EB-SF, you're not thinking about a Noveske barrel? Got a good start on a complete Noveske gun, piece by piece.

Might as well.

I've been looking at the Daniel Defense barrels and haven't really thought about Noveske. My rifle is pretty much Frankensteined- have Noveske upper/lower, DD LPK, Magpul grip and stock, Spike's mil-spec buffer tube, BCM BCG and charging handle. Had to take a break for a while and now its time for front end stuff. Want to get it finished really bad.

[Guest 6.8 AR]

I feel your pain. All of mine are Frankensteined! Order a part here and there, wait for them to arrive, play

on internet, do chores, wait some more, etc. Finally one gets halfway built!

[CQB Elite]

I feel your pain! Its also easier to fly the parts in under my wife's radar if I do them a little at a time.....

[Guest 6.8 AR]

That's always helpful. Their radar is on all the time.

[gjohnsoniv]

It's also very sensitive, the smallest item will alert them.

[Dolomite_supafly]

Wow, I must be a lucky man.

She tells me to buy what I want and I am the one who generally has second thoughts. She pushed me to spend the $200 for a suppressor. She has been pushing me to buy a MG for years but I haven't settled into that one yet because of the cost. And anytime I complain about something not being good she tells me to buy something better.

It might be because she likes to shoot as well. She has several guns (actually she has almost as many as I do) and regularly shoots them.

Seriously though, anytime I have been debating on whether to buy something she tells me to just buy it. I don't need her approval to do any buying but I don't need to hide it from her either.

Dolomite

[mikegideon]

Most of us already knew that Tulip is a keeper .

Now, back to the thread... I'm gonna order this, since I don't have a lathe...

http://www.brownells.com/.aspx/pid=20220/Product/AR-15-M16-UPPER-RECEIVER-LAPPING-TOOL

[Guest 6.8 AR]

Oh rats, I thought you might. I was going to borrow it.

Edited April 9, 2012 by 6.8 AR

[mikegideon]

You're welcome to it. Pulling the barrel on my long range rifle is gonna be like a breach birth.

[Guest 6.8 AR]

No, I meant a lathe, but that will do.

[Guest nysos]

So Dolomite,

When do you want me to bring my AR over for this treatment?

[Guest mr_b8908]

The keyhole marked uppers are manufactured by cerro. As mentioned before, they are seen many high end and low end ar's. Kinda make you wonder how much you paid for a companys name/marking to go next to it.

Great write-up!

Sent from my BlackBerry 9700 using Tapatalk

[Dolomite_supafly]

The upper is a small part of the total cost of an AR. And basing the quality of an entire firearm on only the upper is like basing the quality of a car because of the tires it wears.

There is a lot more that increases the cost as well as quality of an AR other than the upper. And along with the quality parts which do cost more you also get customer service which also increases the cost and value of an AR. That is why a homebuilt AR will sell for less than a comparable factory built gun.

Customer service goes a long way. Look at Leupold scopes, they are far from the best bang for the buck for most of their line of scopes. But what you get with your Leupold scope is probably the best customer service in the industry. And that customer service does have a value for most people.

Dolomite

[141FE]

Do you also square the barrel extension with the bore?

[141FE]

Sorry, double post.

Edited May 2, 2012 by 141FE

[Dolomite_supafly]

There is the locator pin the is in the way. With it in place you generally can't. And the mounting surface is pretty square or at least a lit more square than the upper surface it mates to.

Dolomite

[Paradude54]

I've done this with every AR-15 that I've built and it does make a difference. It doesn't matter who makes the upper, that area of the forging or casting is not going to be square unless they've done it themselves and I do not know of any factory that does this on stripped uppers that they sell and very few do it on the guns that they build themselves and sell you.

The barrel extensions, as Dolomite pointed out, have a locator pin in the way, but I've measured a number of them with a depth dial indicator around the circumference and could not find any discrepencies of note on the ones that I've looked at, so I don't look anymore.

[Guest kingarmory]

Good advice. A lot of people assume that AR receivers are straight and that is seldom the case. Forged receivers have different stresses in different areas, its the nature of forging metals. No two AR receivers are the same, its always a good idea to check and true the critical spots on them. Good tutorial on this Dolomite