Don't know if anyone is looking for an AR-10 receiver lapping tool...  I was searching and couldn't find any and was going to have a buddy machine one up.  I actually found this googling the material specs, wouldn't show up on a straight search or maybe my search-fu is weak.



Anyway, just wanted to share.



http://pacifictoolandgauge.com/ar-tools/10318-ar-15-upper-receiver-lapping-tool.html

I thought $28 from Pacific Tool was a good deal.  They have the AR15 tool also, same price.

thanks for posting this, i looked all over when i assembled mine and couldn't find any. i ended up building without lapping the upper. i'm going to buy it and when i have time i'll tear the upper down and do it. once again thanks for posting!



Bruce

How much was shipping?

Who makes your uppers? When i swapped my barrel in my armalite, i had the smith who pinned my front sight check the upper. It was square and didn't need anything.

Just saying maybe check the upper first before you start lapping it.

I used an Aero upper.  The tool cut a small amount more on one side, but not too far off.

Thanks, I've searched everywhere, I thought ..for a AR10 tool.
Just ordered.

That upper was a prime candidate to be squared. Sometimes it may make no difference. But that small bit could have thrown you off past 500yds. Those small mistakes really amplify down range. Some things you'll never see under 500yds.

I had my Aero AR15 receivers checked, they were good to go as well. Shit happens. That's why it pays to be anal with these 308 builds

$9.30 USPS Priority Mail to North Texas

can't cry over that.



Bruce



 

Here is the one I bought.



M5 upper after I lapped it this morning.

Nice.

Thanks. I doubt the G&G is any better than OP's tool, but I figure it's worth mentioning for future reference in case either of the companies stop offering the lapping tools.

 

I face mine with some sandpaper laying on a flat surface.  I did one rifle that needed about 20 clicks to zero, and when I was done lapping it, it only needed 3 or 4 clicks to zero.

Thanks for the link. I've been waiting for someone to make a larger one.

Geeze. And to think I had one turned for me a few years ago.... and it cost me nada!

Thx for the link

I am sooooo tempted to do this on my current carbine build that I am getting ready to finish....just as an experiment to see how much I can wring out right off the bat.



On my last build I ended up yanking the barrel, CeraKoting the extension and replacing the Apex guard with a JP forend and, after also replacing the offending gas tube and gas block went from this goofy shit:






to THIS

Why would lapping the face of the receiver tighten up your groups?

How many shots in the bottom group?

 

What was happening?

In that instance, the bottom group was just a 3 shot because I was so damn sick of dealing with that gun.  But that group proved IMMEDIATELY that I had fixed the issue because at no time prior had I been able to get a cold shot and the rest of a group to sync.   Now, my cold shots and the rest of the group are properly "mathematical" instead of wildly influenced by an overabundance of acute external forces.
The issue in the top pic was predominately caused by using a Wilson gas tube and adjustable block and by me being an idiot.
The true position of the gas port in the block was off by .037 thou from the factory.  SO, I milled .037 off the block to get the barrel port and the block port to line up.  So guess what that effectively did to the gas tube?  Yup...made it long enough (effectively) to impinge upon the carrier key....and YUP, that was enough force to cause the barrel to do all kinds of wild shit.  I was able to shorten the tube a bit and it still ran fine....and as the tube got shorter, the groups got better....but they always looked like that top pic.
Sooooo, during the initial diagnosis I just wasn't sure if the gas tube was all of the problem (and I normally do not do this) so I also changed the two other things I thought might be influencing issues: the handguard system and the receiver extension fit.
Mind you, I proved the gas tube was definitely causing at least much of the problem and changing to a Syrac block and a normal gas tube instead of the Wilson straight model probably would have fixed it completely......BUT.....I never liked the fit of the extension to the upper so I shimmed it.  Since the gun is REALLLLY heavy, I went to a stiffer forend ( Jp ).
Now, I've only been out a few times since then but when my nephew was last home on leave, we went out and shot off of a cheap picnic table in gusting 25mph winds and had a hell of a hard time NOT shooting under 1.25 MOA and those were 5 shot groups.  That's with NO bags...just off the bipod on a cheesy picnic table.
Here is the gun BEFORE I changed it up and before I got the stock adjusted, an MDT butt pad installed, etc....I really need a great pic of it since then because it hardly looks like this gun any more. It's a beast and it shoots like a dream!!!!!!
I will make it a point to get some pics not only of the gun but of my groups with GI Spec ( 149 grain ) or my handloads ( various 165 to 178 grain ) that I have cooked up.

NOTE: that Apex handguard is now on my carbine, the long rifle sports a Jp tube......I am sure that the Apex and this carbine will rock the house, proving my original theory that it was the gas setup that caused the problem.  I do not know WHY the tru pos was off so much on the Wilson block but I bet it has to do with that block being more for Wilson's .308 barrels.  Oddly, in an attempt to do nothing but the best....I inadvertently caused a problem that had me chasing my tail for the better part of 3 months. ( one has only so much time to choot when you go to school, work 60 horu s aweek and have tons of divorce debt to pay off ) .....  I really learned a valuable lesson.







 

Tool ordered.  Gonna go for it.  Though my carbine will wear a red dot at the end, I am gonna run a scope on it ( 3 X 9 Zeiss ) at first and see how well it shoots.
Gonna use my Cera Kote shim method again....might as well go all the way.  Let's see what this thing can do.
This is the mock up....barrel is off getting the gas block fixed to it.  The upper will be completely re-stripped and I'll shim the extension and true the face prior to installation.  I'll put a VERY thin layer of KG Guncoat over the exposed aluminum just as a precaution against any galvanic activity between raw aluminum and the steel of the barrel nut and the barrel seat..  My KG is the Hi PTFE black Gun Kote...should be a pretty decent insulator.












 

Hey desertmoon can you post a link to the thread where you were talking about shimming your upper with Cerakote?

Thanks

Double tap

Sure can.  Gimme just a moment.





ETA:





http://www.ar15.com/forums/t_3_121/694677_What_bedding_compound_ya_ll_using_on_A10_barrel_extension_to_upper__.html





Lot's of good stuff int hat thread.





Specifically, I mix up a small batch of Graphite black....( color really isn't that important as this is not intended to move ) and thin it with MEK by about 10 percent MEK substitute ( or MEK ) by volume.  





I  LIGHTLY....OH SOOOOO LIGHTLY sand the extension with 800 grit automotive paper.  It's just to give it a cross hatched texture for the C-Kote to bond to. Then I coat the extension, masking the throat and the face of the barrel seat first. I then cure the CeraKote per the instructions after applying the coat.





I use a standard pill bottle that is cut into a 4/5ths circle and some use some very thin double sided tape to secure more of the automotive grade paper inside the circumference of the pill bottle.





I test fit the extension until it begins to bind....once the resistance becomes kind of firm, I STOP and pull the barrel and wet sand it very lightly with the pill bottle "reverse mandrill".  Dry off the extension and start fitment again.  I do not force fit the extension, I try for the tightest slip fit I can get.





You have to wash your sanding mandrel frequently as paint loads paper really fast.





Once I have a full, smooth seat, I wash the barrel and the upper completely and then dry them.  Then it's assembly time.





This time I am going to true to receiver face prior to shimming.
TIP:  have a heat gun handy.....if you stick the barrel, you can get it off with some help and a heat gun.  You will likely have to start over if the paint peels from the heat.
 

See above

Why not just make it an interference fit and use heat to get it in?

I went with blue loctite when I bedded this 6.5 Criterion barrel earlier today.

Oh, I tried.....and I failed...SPECTACULARLY.



 

Thanks for the heads up OP I've been looking for one for a while

Aaaannnnnd they finally got around to shipping it today (supposedly). No idea why it took them so long to get it shipped when there were supposedly over 100 in inventory when I made the order.

Got mine in the mail today.
Nice and snug fit in an Aero upper.

Hoping to get mine this week.  Just found out my upper gas block pinning is done....BUT I have my port door and my hand guard caps getting re-painted so I am hoping those get done this week.  I jut didn't feel like doing them myself.



Hope to have the tool SOON so I can get to work and get this thing together!!!!





 

THANK YOU FOR POSTING!!!!!!   I traded into a rifle that's doing exactly what your pics show.  I figured it was something to do with the barrel fit, and now I know to look at my gas tube as well.  My receiver block in on the way and I already have a lapping tool so lapping/bedding is going to get done while I have it torn down.  It's nice to see some real before/after pics.

Thanks for the pics, ordering lapping compound today.
Smith is finishing up my brake and is gonna kote 1/2" of the barrel extension per John Burns tip from the other thread.

Just picked up my upper from my smith.....still waiting on my lap tool and my parts from my painter.  Which is funny because I have to paint the extension ANYHOW....why did I send of other stuff to be done?



Oh, that's right...BECAUSE I'M STUPID!!!!!!!!!!!!!