trueing the face of your AR upper receiver.

[SheepDog223]

Has anyone heard of trueing the face of an AR upper? Where the barrel es in and rests I have been convinced that the surface of the upper receiver is not true. When you tighten the barrel but to the upper your barrel will be influenced by the uneven surface and minutely corupted to an angle. The barrel on my next gen was pitched down and left.
For those of you who zero at 100 and shoot at 100 this is unnoticeable and doesn't matter.
For those of you who like to use the turrets on your scope you may be a better shooter than you thought you were.
If your scope is straight and your barrel is just a bit off any adjustment you make to your scope will not be honored by your barrel.

The only guy I know of who is doing this is Will at HX2 arms in Salem.

Your thoughts?
Your opinions?
Your facts?

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[edslhead]

Unless the barrel is flopping around ( moving) , the scope should still zero up?

 

[SheepDog223]

Sure it'll zero up. But if the scope is straight and the barrel is .01° off every scope adjustment you make will not transfer to the line of trajectory.

 

[edslhead]

Yep, but it would have to be pretty far out whack to have more effect than even the smallest human error. Kinda sounds like over kill in precision to me. You scope, height wise is never in line with the barrel anyway. Maybe if you were building a rail gun .

 

[SheepDog223]

The scope isn't centered on the lateral but it is centered on the vertical. Aim small miss small my friend. Maybe this discussion would better fit in the snipers hide forum.

 

[Certaindeaf]

Maybe you should draw us a picture.

 

[edslhead]

Well you might be onto something. I just think if it was a big problem it would have been addressed more publicly by now.

 

[SheepDog223]

http://www.brownells.com/gunsmith-t...16-upper-receiver-lapping-tool-prod20220.aspx

That's what sailors must have said about putting a diesel in a ship.

 

[edslhead]

I am kinda old. I just meant your ability to hold the gun exactly vertical might be a bigger factor than having the barrel trued to the upper. I see where truing it up would leave you with one less excuse for missed shots.

 

[SheepDog223]

Oh... I didn't think of that. Sometimes I need all the excuses I can think of. Dang it why'd you have to bring that up...

 

[Member 5605]

One of my rifles is canted a little to the left. Seems most of my barrels cant left.

May be worth it if I do a heavy barrel setup or precision rifle soon.

 

[Velzey]

No I've never had to do it do any of the gazillion precision AR's I have built. But if you have some out of spec parts you could face the receiver!

 

[SheepDog223]

gazillion? Wow!

 

[Certaindeaf]

gazillion? Wow!

I think he just drew us a picture.

 

[Velzey]

The first thing you do when you face off a receiver is remove the hard anodize. Exposing the soft aluminum. I don't mess with an out of square receiver I send it back and get another! Not worth the setup time or the money spent for having the anodize stripped and reapplied!

 

[Medic!]

The M1C and M1D had a left side offset scope. If zero was at 100 yards. The round would strike to right of the crosshairs out to 100 yards. Then the strike would be off to the left.

So you are shooting across the point of impact from right to left.

If you zero further away than 100yds you can spread this variance out. Because the variance from right to left will always be the difference between the scope center. And the center of the barrel. Weather you spread it out over 100yds or 500yds.

Or you can just zero the scope to the left of impact. If you match the scope offset. The round will always impact the same distance to the right out to any distance.
At 500yds a consistent 1-1/2'' offset wont be that bad. Or just use the crosshair center as a reference. And understand the round will always impact just to the right.

With the AR I would think the center of the scope, at it's internal adjustment point would be so close to the center of the barrel. That you would be good out to the 400 or so yards the round is good for.

But if it was 1/4'' to the left. And zeroed at 100yds. The impact would be 1/4'' left at 200yds. 1/2 at 300. And so on.

Go shoot your gun and compare POI with a 100yard zero and same zero at 400yds.
I don't think there will be any big variance.

Sorry so long winded. I cant draw pictures.
But I'm good at making up stories.

 

[mjbskwim]

The first thing you do when you face off a receiver is remove the hard anodize. Exposing the soft aluminum. I don't mess with an out of square receiver I send it back and get another! Not worth the setup time or the money spent for having the anodize stripped and reapplied! View attachment 253548

Very good point here. It would seem if you didn't reparkerize the face you could have issues after a while with the face deforming or shortening up,changing the head space
BTW wouldn't doing this change the head space?
And I have never heard of this so I have never done it with the half gazzillionnss of ARs I have put together. (maybe 10)
I am going out to the shop and checking my 2 receivers though

 

[SheepDog223]

Does it change the headspace? If the bolt locks into the lugs just the same?

 

[Heywood]

Has anyone heard of trueing the face of an AR upper? Where the barrel es in and rests I have been convinced that the surface of the upper receiver is not true. When you tighten the barrel but to the upper your barrel will be influenced by the uneven surface and minutely corupted to an angle. The barrel on my next gen was pitched down and left.
For those of you who zero at 100 and shoot at 100 this is unnoticeable and doesn't matter.
For those of you who like to use the turrets on your scope you may be a better shooter than you thought you were.
If your scope is straight and your barrel is just a bit off any adjustment you make to your scope will not be honored by your barrel.

The only guy I know of who is doing this is Will at HX2 arms in Salem.

Your thoughts?
Your opinions?
Your facts?

Yes. I have done it. And I have bought receivers that do not need it, if you are trying to build a tack driver, not doing it is silly. It takes so little effort. There are some that swear by it. I haven't, but others have done accuracy tests before and after and they do see a difference. I also lap the carrier race way and bed the extension to the reciever if it is loose. I also bed the gas block. The result is a better than 1/4min. AR15 built in my garage. Many who do not do it still think a semi auto can not be as accurate as their hunting rifle.

 

[Certaindeaf]

Yes. I have done it. And I have bought receivers that do not need it, if you are trying to build a tack driver, not doing it is silly. It takes so little effort. There are some that swear by it. I haven't, but others have done accuracy tests before and after and they do see a difference. I also lap the carrier race way and bed the extension to the reciever if it is loose. I also bed the gas block. The result is a better than 1/4min. AR15 built in my garage. Many who do not do it still think a semi auto can not be as accurate as their hunting rifle.

Dood.. a 1/8 MOA garage built AR that's as accurate as a 2 MOA hunting rifle? Wow.
This is exactly why I use a shotgun on those 25yd beer cans! blammo!