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5/4/2017 5:32:54 PM EDT
I hope this is the right section.

I was looking at getting an AR15 upper lapping tool for my first AR15 build as it is a precision oriented build using the 6.5 Grendel. I saw Brownells had free shipping for today(use code: M5S) so i was going to purchase theirs, then i saw their reviews. It seems that it is made of soft steel so it deforms easily from use, and it seems every single one is made out of spec. Does anyone know of a good AR15 upper lapping tool that doesnt cost an arm and a leg(seriously, i am probably only going to use it once for a very long time.).

Brownell's monstrosity
5/4/2017 5:54:02 PM EDT
[#1]
Odds are this is the best one on the market but I see now it is no longer a stocked item and "made to order".

PTG Lapping Tool

It's waaaay better than the Wheeler Engineering lapping tool and has to be better than the Brownells if theirs is soft.
PTG tool worked great for me.....


5/4/2017 6:35:57 PM EDT
[#2]
Quote History
Quoted:
Odds are this is the best one on the market but I see now it is no longer a stocked item and "made to order".

PTG Lapping Tool

It's waaaay better than the Wheeler Engineering lapping tool and has to be better than the Brownells if theirs is soft.
PTG tool worked great for me.....

http://i77.photobucket.com/albums/j69/maximusscriptorius/95EA8434-A6EF-4FAF-875A-1C47F0C390CF_zpsaypsdk89.jpg
http://i77.photobucket.com/albums/j69/maximusscriptorius/117B3F24-CA9A-44DC-8CA5-70E8590D8017_zpsuamjcwkb.jpg
View Quote
Thanks man. I will have to take a look then. To bad they dont offer it for rent becuase as i said, i am probably going to only use it once, for now.

Did you use a clamshell to hold the upper receiver, or did you just chuck it up in a vise?
5/4/2017 9:30:29 PM EDT
[#3]
That's odd. I have a Brownell's lapping bar that I've used about 15-20 times and it's fine...

If this is something you'll be using a few times in your lifetime, I'm sure their tool will be just fine.
5/4/2017 9:49:32 PM EDT
[#4]
I tried the wheeler one, it's not that nice, but did the job. I had a receiver that sights were way off, so figured what the hell give it a shot. Haven't re zeroed yet, but it definitely took material off one side first, then evened out.
5/5/2017 1:04:10 PM EDT
[#5]
Quote History
Quoted:
That's odd. I have a Brownell's lapping bar that I've used about 15-20 times and it's fine...
View Quote
+1

I have at least that many on my Brownell's too. No problems what so ever.
5/5/2017 4:23:46 PM EDT
[#6]
Is this something I should be doing? I have read about many times, just never tried it. Do you just coat the surface with a blue stick or something when done? I am going to research this, just need to know if I should buy one of these to make sure my Ar's hit like they should. <sorry for any hijack>
5/5/2017 4:43:03 PM EDT
[#7]
Like you, I'm putting together a precision build and wanted the barrel extension to be as true as possible. All of the tool for doing this have spotty reviews and I didn't want to make a bad situation worse. A member posted here about Paladin Machine Shop services and they offer receiver truing for $10 plus return shipping. Sent them 2 uppers and had them back in a couple days and the extensions came back beautifully flat. It was a light year better job than I feel I could have attained using a universal tool and valve grinding compound. They were really helpful and we were in regular contact via email. For the record, I don't work for Paladin or receive financial compensation form them. Just a guy passing along a referral that was passed to me on this board.
5/5/2017 8:02:35 PM EDT
[#8]
Quote History
Quoted:
Like you, I'm putting together a precision build and wanted the barrel extension to be as true as possible. All of the tool for doing this have spotty reviews and I didn't want to make a bad situation worse. A member posted here about Paladin Machine Shop services and they offer receiver truing for $10 plus return shipping. Sent them 2 uppers and had them back in a couple days and the extensions came back beautifully flat. It was a light year better job than I feel I could have attained using a universal tool and valve grinding compound. They were really helpful and we were in regular contact via email. For the record, I don't work for Paladin or receive financial compensation form them. Just a guy passing along a referral that was passed to me on this board.
View Quote
That is awesome! Do you have a link to the website or an email to contact them with? I don't think i found the right shop using google.
5/5/2017 8:13:22 PM EDT
[#9]
Quote History
Quoted:
Is this something I should be doing? I have read about many times, just never tried it. Do you just coat the surface with a blue stick or something when done? I am going to research this, just need to know if I should buy one of these to make sure my Ar's hit like they should. <sorry for any hijack>
View Quote
No need to be sorry. It really isnt a hijack, just a side question. It isnt something you have to do, but if you are building a gun for absolute precision it is just one of the many little thing you can do to help. Lets say you have a receiver with a face that is proud on one side more than the other. Then you will have to compensate with a lot of extra windage adjustment. Have you ever seen one of those AR15 with iron sight were to zero it the windage was cranked all the way to one side. Imagine something like that, but not so severe.

We haven't even talked about bedding the barrel to the upper receiver!
5/5/2017 11:55:41 PM EDT
[#10]
Quote History
Quoted:


We haven't even talked about bedding the barrel to the upper receiver!
View Quote
OK-
I did this for the first time a few weeks ago. Not much to it.
Did mine this way: To find out what shim stock to buy- took apart my feeler gauge set and wrapped an individual gauge around the barrel extension and then inserted it into the upper. In my case, a  .002" feeler gauge was perfect.
Ordered a sheet of .002 shim stock from McMaster Carr for $7.31 (#9011K813) and cut a strip about 15/16" wide and long enough to wrap completely around the barrel extension minus locating pin (@ 3 1/16").  After cleaning the inside of the receiver bore, the barrel extension, and both sides of the shim with degreaser (with automotive brake and parts cleaner) I spray a nice coating of Loctite Clean and Cure Primer to all of the parts and let dry. Then I coated all of the same surfaces individually with Loctite 641, wrapped the shim around the barrel extension and assembled as normal. Coating all of the surfaces will assure that there are no air gaps and you have a complete lock up and bonding of your barrel to your upper. The Clean and Cure Primer insures that Loctite will cure quickly and completely. But be careful with it- Loctite products will literally dry before your eyes when they touch it- so assemble quickly.


5/6/2017 12:04:35 AM EDT
[#11]
Quote History
Quoted:
OK-
I did this for the first time a few weeks ago. Not much to it.
Did mine this way: To find out what shim stock to buy- took apart my feeler gauge set and wrapped an individual gauge around the barrel extension and then inserted it into the upper. In my case, a  .002" feeler gauge was perfect.
Ordered a sheet of .002 shim stock from McMaster Carr for $7.31 (#9011K813) and cut a strip about 15/16" wide and long enough to wrap completely around the barrel extension minus locating pin (@ 3 1/16").  After cleaning the inside of the receiver bore, the barrel extension, and both sides of the shim with degreaser (with automotive brake and parts cleaner) I spray a nice coating of Loctite Clean and Cure Primer to all of the parts and let dry. Then I coated all of the same surfaces individually with Loctite 641, wrapped the shim around the barrel extension and assembled as normal. Coating all of the surfaces will assure that there are no air gaps and you have a complete lock up and bonding of your barrel to your upper. The Clean and Cure Primer insures that Loctite will cure quickly and completely. But be careful with it- Loctite products will literally dry before your eyes when they touch it- so assemble quickly.

http://i77.photobucket.com/albums/j69/maximusscriptorius/6F904FBC-50BE-4996-BF4B-5F753CEF4493_zpsxrtocpco.jpg
http://i77.photobucket.com/albums/j69/maximusscriptorius/94DFCD2B-9053-4A34-BA75-4F7AED44C1E7_zpsgm19api9.jpg
View Quote View All Quotes
View All Quotes
Quote History
Quoted:
Quoted:


We haven't even talked about bedding the barrel to the upper receiver!
OK-
I did this for the first time a few weeks ago. Not much to it.
Did mine this way: To find out what shim stock to buy- took apart my feeler gauge set and wrapped an individual gauge around the barrel extension and then inserted it into the upper. In my case, a  .002" feeler gauge was perfect.
Ordered a sheet of .002 shim stock from McMaster Carr for $7.31 (#9011K813) and cut a strip about 15/16" wide and long enough to wrap completely around the barrel extension minus locating pin (@ 3 1/16").  After cleaning the inside of the receiver bore, the barrel extension, and both sides of the shim with degreaser (with automotive brake and parts cleaner) I spray a nice coating of Loctite Clean and Cure Primer to all of the parts and let dry. Then I coated all of the same surfaces individually with Loctite 641, wrapped the shim around the barrel extension and assembled as normal. Coating all of the surfaces will assure that there are no air gaps and you have a complete lock up and bonding of your barrel to your upper. The Clean and Cure Primer insures that Loctite will cure quickly and completely. But be careful with it- Loctite products will literally dry before your eyes when they touch it- so assemble quickly.

http://i77.photobucket.com/albums/j69/maximusscriptorius/6F904FBC-50BE-4996-BF4B-5F753CEF4493_zpsxrtocpco.jpg
http://i77.photobucket.com/albums/j69/maximusscriptorius/94DFCD2B-9053-4A34-BA75-4F7AED44C1E7_zpsgm19api9.jpg
Awesome way to bed an upper. To bad i dont have any more feeler gauges. Long story!
5/6/2017 9:26:12 AM EDT
[#12]
Quote History
Quoted:
OK-
I did this for the first time a few weeks ago. Not much to it.
Did mine this way: To find out what shim stock to buy- took apart my feeler gauge set and wrapped an individual gauge around the barrel extension and then inserted it into the upper. In my case, a  .002" feeler gauge was perfect.
Ordered a sheet of .002 shim stock from McMaster Carr for $7.31 (#9011K813) and cut a strip about 15/16" wide and long enough to wrap completely around the barrel extension minus locating pin (@ 3 1/16").  After cleaning the inside of the receiver bore, the barrel extension, and both sides of the shim with degreaser (with automotive brake and parts cleaner) I spray a nice coating of Loctite Clean and Cure Primer to all of the parts and let dry. Then I coated all of the same surfaces individually with Loctite 641, wrapped the shim around the barrel extension and assembled as normal. Coating all of the surfaces will assure that there are no air gaps and you have a complete lock up and bonding of your barrel to your upper. The Clean and Cure Primer insures that Loctite will cure quickly and completely. But be careful with it- Loctite products will literally dry before your eyes when they touch it- so assemble quickly.

http://i77.photobucket.com/albums/j69/maximusscriptorius/6F904FBC-50BE-4996-BF4B-5F753CEF4493_zpsxrtocpco.jpg
http://i77.photobucket.com/albums/j69/maximusscriptorius/94DFCD2B-9053-4A34-BA75-4F7AED44C1E7_zpsgm19api9.jpg
View Quote
When you used the feeler gauge, how did you know that you had the right one?

I ask because I'm very interested in this technique and will likely try it myself. Also is your barrel new and if not did you happen to record its accuracy for a before and after comparison?
5/6/2017 10:09:55 AM EDT
[#13]
Quote History
Quoted:


When you used the feeler gauge, how did you know that you had the right one?

I ask because I'm very interested in this technique and will likely try it myself. Also is your barrel new and if not did you happen to record its accuracy for a before and after comparison?
View Quote
Trial and error for the feeler gauge. Wrap the thickest one you can that will still allow you to insert the extension. The .002" gauge took all noticeable felt slop from the barrel. The loctite will do the rest.
At first I thought the upper receiver was out of spec but I tried the barrel (LaRue Stealth 20") in three other uppers and it had the same fit so instead of searching for another upper that was at the bottom of the spec for the bore diameter, I decided to bed it.
This was a fresh build so I don't have a "before and after" story. The affect that this has on accuracy is probably debatable and don't even know if I can shoot well enough to see the merits of this procedure. I just wanted to remove one more variable from the precision shooting formula so I can always fall back on "its me-not the gun". If the gun is right, it must be the shooter

References: Hellbenders Guide
Archived thread
5/6/2017 10:40:00 AM EDT
[#14]
When shimming a barrel extension, don't go crazy and make the extension so large in diameter that you have to pound it in.  And once you've applied the shim, take care to align the barrel very carefully as you start it in the upper.

Shims are worlds more precise than using any form of thread locker or epoxy compound for "bedding" an AR barrel in the upper.  And frankly, if you're going to take the time to true the face of your upper, it shouldn't be any problem to take the time to effectively and properly center the barrel in the upper.
5/6/2017 9:06:45 PM EDT
[#15]
I maybe doing something wrong. I just measured my barrel extension and the upper receiver. For the barrel extension i got 1.002 inches, for the Anderson upper receiver i got .998 inches.
5/6/2017 9:25:19 PM EDT
[#16]
What brand of calipers are you measuring with? Unless it's a quality set (Mitutoyo, Starrett, Brown and Sharpe), the jaws ID to OD relationship isn't guaranteed to be ground dead nuts to each other.
5/6/2017 10:24:42 PM EDT
[#17]
My calipers and micrometer never left the drawer when I did this. It was done by feel. The bottom line is that the barrel still has to slide into the upper receiver using hand pressure. You'll know that you have the right shim when you can still assemble easily and most or all of the slop is gone.
5/6/2017 10:30:36 PM EDT
[#18]
Quote History
Quoted:
I maybe doing something wrong. I just measured my barrel extension and the upper receiver. For the barrel extension i got 1.002 inches, for the Anderson upper receiver i got .998 inches.
View Quote
I'm guessing that there is something going on with your measurements because this indicates an interference fit of .004 inches. If your barrel slips into your upper easily then your measurements are off. If not then you have no reason to shim. Barrel goes in the freezer and upper gets heated with a heat gun or goes in the oven. Once you put it together and the temperatures stabilize, you are bedded.
5/7/2017 1:37:47 AM EDT
[#19]
Brought the Palidan thread back up for those that may need it.
5/7/2017 2:52:24 AM EDT
[#20]
Quote History
Quoted:
When shimming a barrel extension, don't go crazy and make the extension so large in diameter that you have to pound it in.  And once you've applied the shim, take care to align the barrel very carefully as you start it in the upper.

Shims are worlds more precise than using any form of thread locker or epoxy compound for "bedding" an AR barrel in the upper.  And frankly, if you're going to take the time to true the face of your upper, it shouldn't be any problem to take the time to effectively and properly center the barrel in the upper.
View Quote
x2 for just the shim

I just cut a notch in the shim for the alignment pin before wrapping it around the extension and lightly tap the barrel in with a wooden mallet. Slides right in.  

I have the Wheeler lapping tool and it wobbles way too much with the flexible shaft. I'm cutting the flex shaft off before using it again and chuck the drill to the remaining hex nut.
5/7/2017 10:12:35 AM EDT
[#21]
Double Post - please ignore or delete.
5/7/2017 10:13:09 AM EDT
[#22]
Another double post, darn - sorry guys - ignore or delete this.
5/7/2017 10:17:03 AM EDT
[#23]
Quote History
Quoted:
Like you, I'm putting together a precision build and wanted the barrel extension to be as true as possible. All of the tool for doing this have spotty reviews and I didn't want to make a bad situation worse. A member posted here about Paladin Machine Shop services and they offer receiver truing for $10 plus return shipping. Sent them 2 uppers and had them back in a couple days and the extensions came back beautifully flat. It was a light year better job than I feel I could have attained using a universal tool and valve grinding compound. They were really helpful and we were in regular contact via email. For the record, I don't work for Paladin or receive financial compensation form them. Just a guy passing along a referral that was passed to me on this board.
View Quote
Would this be the guy at [email protected]? I appreciate it. I would like to do this myself since I have so many uppers but I will inquire about his service.
5/7/2017 10:18:20 AM EDT
[#24]
Hello All,
As some of you know I have several builds and upgrades going on right now. I want them as precise as possible. I want to do this lapping process but I am finding too much contradicting information. I understand you need a quality tool, I will get that.

1. However, I don't understand about the compounds, what are good to use? Brownells sells a 600 grit one - is this what I want?

2. Also, I understand I need to "bed the barrel," after this is done. Many use Loctite 620 - is this correct?

3. I understand that bedding it is mainly putting the Loctite on the extension liberally and inserting it - am I wrong here?


I appreciate the help so much!
5/7/2017 1:17:48 PM EDT
[#25]
Quote History
Quoted:

2. Also, I understand I need to "bed the barrel," after this is done. Many use Loctite 620 - is this correct?
View Quote
Bedding the Barrel Extension isn't necessary, it will help accuracy but it's not required.

I square the front of my receivers with the Brownells lapping tool but I don't bother to bed the barrel.
5/7/2017 4:56:22 PM EDT
[#26]
I appreciate that advice, I am thinking about it but not sure on the bedding. Also I am still unsure on this:

1. However, I don't understand about the compounds, what are good to use? Brownells sells a 600 grit one - is this what I want?

2. Also, I understand I need to "bed the barrel," after this is done. Many use Loctite 620 - is this correct?  (May need to, hearing I don't have to)

3. I understand that bedding it is mainly putting the Loctite on the extension liberally and inserting it - am I wrong here?

Thanks in advance guys
5/7/2017 9:32:46 PM EDT
[#27]
Quote History
Quoted:
I have the Wheeler lapping tool and it wobbles way too much with the flexible shaft. I'm cutting the flex shaft off before using it again and chuck the drill to the remaining hex nut.
View Quote
I believe that a power drill should NEVER be used with an upper lapping tool.  Firstly, it gives you the impression that you have to take off a lot of material - why do you need a power drive if you don't?  And using a drill takes away the "feel" for lapping the surface of the upper.

ALL you need to do is to make the face of the upper true to the bore.  That could mean just taking off some uneven anodizing.  You do not need to have shiny aluminum all the way around for the face to be square and true to the bore.  Doing the task by hand will encourage you to turn a little, check often, and be as conservative as possible.
5/7/2017 10:10:37 PM EDT
[#28]
Quote History
Quoted:


Would this be the guy at [email protected]?
View Quote
yes, that's the guy.


i use a cordless drill, at very low speed.  how slow?  only way i can describe it as maybe 1 rpm, in that ball park.  pretty slow.  i don't think it's more than 2 rpm.  mainly to keep the heat out of the compound and surface, otherwise weird things happen that are not good: galling, which then leads to chunking, which may then cause depression.

and even with the cordless drill, it still takes about half hour to do one.  lapping for about 15-30 seconds, pull it back about 3/4", un-chuck the drill, get some Q-tips and wipe the receiver face carefully to inspect the progress (flashlight helps).  carefully dab some more lapping compound onto the tool face with a small flat-blade screwdriver, resume.  it's not a fast process.  it is tedious.  it's been about 5-10 iterations for one upper, for me.

when you pull the tool back to check the progress, you have to keep the mandrel away from the accumulating lapping compound at the receiver face, otherwise the mandrel will take the lapping compound into the bore when you push it back in to resume.  and then you have circular marks in the bore anodizing which are there forever, seen by you every time you pull the bolt back on your project AR to personally remind you.

if you got all of this stuff laid out and set up, you might as well do more than 1 stripped upper while you're at it, make it worth your while.  you know, for future builds.  because, nobody builds just one AR upper and stops there.
5/7/2017 10:20:20 PM EDT
[#29]
compounds:
i've used the Brownells 600 grit garnet lapping compound with good results.
i've also used automotive Loctite Clover silicone carbide grease mix 180 grit with, fair-to-good results.

they both work, resulting in a flat surface that's truer than original, obviously the finer compound gives you a smoother surface.  i don't think it takes that much longer with the fine grit because the time consuming part is the interruptions to do the progress inspection.

when the barrel extension crushes onto the lapped receiver face, i don't think it really cares whether it was lapped with 600 grit, or 180 grit.

i use the brownells tool, and the PTG tool.  i had one (and only 1) instance where the PTG would not fit the bore, but the brownell's did, smoothly.  so i checked the receiver fit with the intended BCG and it's fine.  so, no issues.  it was a discovery.  i've been using the PTG though, mainly, it's newer (less worn face).

the PTG also has a longer shank, that helps with getting the drill lined up, collinear with the receiver bore, otherwise your hands will detect the wobble when you start, but, no biggie.

i lightly grease the receiver bore, and the mandrel on the tool with plain old wheel bearing grease (not the expensive stuff).
5/7/2017 11:03:15 PM EDT
[#30]
The Wheeler kit worked well for me.  It includes the lapping compound.  I used a battery operated slow nut driver with it.  Just enough to remove the anodizing all the way around brought the rear sight from far left zero back to center zero.

5/8/2017 6:33:39 AM EDT
[#31]
The problem I see with these lapping tools is that there is no way to check concentricity.

Unless the upper is put on a lathe and that surface is measured with a dial indicator there is no way to check how true that surface is.

I've got two stripped uppers I want do this to but I don't have access to lathe or a mill or a dial indicator.

I think I'm going to find a place that does this.
5/8/2017 8:25:22 AM EDT
[#32]
Okay, I am probably going to send mine off to have them done. Let me ask this, what about the missing anodizing? Do you take a touch-up pin to it? I want to keep it from corroding.
5/8/2017 7:16:43 PM EDT
[#33]
I bought the tool from Brownell's and the compound, 600 grit. I am going to see how it works. I figure if I go slow I can do a decent job. I was going to send my receivers off and have it done, but I just did not want to send so many of them off at once to get the 10 dollar price and I honestly have many to do. We will see if I regret this or not. I imagine if I go slow, and perhaps use it vertically as to allow gravity to assist me, I could do it. I bet I can turn it by hand. I don't have a problem spending an hour per receiver. Let's hope the tool from Brownell's is not subpar. Some seem to have great results, others, not so much. I will report back. The only thing that bugs me is that I have no way of making sure the surface is true, the machine shop would have ensured that - but again, I just did not want to send that many receivers out. Also, I just sent a barrel out to have it coated and the company apparently was closed when the postal worker came by and they left one of those notices...so now my barrel is floating between the post office and the company...I am kicking myself for not having it cerekoted locally now....
5/9/2017 8:44:29 PM EDT
[#34]
Quote History
Quoted:
I'm guessing that there is something going on with your measurements because this indicates an interference fit of .004 inches. If your barrel slips into your upper easily then your measurements are off. If not then you have no reason to shim. Barrel goes in the freezer and upper gets heated with a heat gun or goes in the oven. Once you put it together and the temperatures stabilize, you are bedded.
View Quote View All Quotes
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Quote History
Quoted:
Quoted:
I maybe doing something wrong. I just measured my barrel extension and the upper receiver. For the barrel extension i got 1.002 inches, for the Anderson upper receiver i got .998 inches.
I'm guessing that there is something going on with your measurements because this indicates an interference fit of .004 inches. If your barrel slips into your upper easily then your measurements are off. If not then you have no reason to shim. Barrel goes in the freezer and upper gets heated with a heat gun or goes in the oven. Once you put it together and the temperatures stabilize, you are bedded.
Ya, it slips in relatively easily. Which is weird, because i wasn't the only person who measured that. I am using some cheap Hornady calipers so there is that. But i didn't think they would be that bad.
5/10/2017 12:41:28 AM EDT
[#35]
Quote History
Quoted:
Okay, I am probably going to send mine off to have them done. Let me ask this, what about the missing anodizing? Do you take a touch-up pin to it? I want to keep it from corroding.
View Quote
Do not worry about the anodizing.  The barrel extension mates to that surface and is torqued to it by the barrel nut.
5/10/2017 9:56:38 PM EDT
[#36]
Before lapping your upper, you might consider this feedback from 2A-Armament:

http://www.ar15.com/forums/t_2_493/269790_Do-I-need-to-lap-a-Balios-Lite-upper-.html

"One thing to consider, and BK already hit it in a more technical sense, is this....

If the lapping tool can fit down the bore, it means that it's sitting inside that bore at an angle. even if it's a thousandth out on that bore, it will translate to a thousandth or more! out of square at the face of that receiver.

You could be doing damage by lapping that face.

EDIT:

After looking at these tools on line, I am going to go ahead and say that they are in fact TAKING THE FACE OUT OF SQUARE of the bore! The bore dimension for the extension is tighter than the dimension on the carrier bore. If you look at these tools, the pilot is inserted, and skips past the tightly held extension bore, and goes into the looser dimensioned carrier bore. So as this tool falls into the carrier bore, it is forcing the laping face out of square with the extension bore.

Ryan "
5/10/2017 11:48:25 PM EDT
[#37]
Quote History
Quoted:
Before lapping your upper, you might consider this feedback from 2A-Armament:

http://www.ar15.com/forums/t_2_493/269790_Do-I-need-to-lap-a-Balios-Lite-upper-.html

"One thing to consider, and BK already hit it in a more technical sense, is this....

If the lapping tool can fit down the bore, it means that it's sitting inside that bore at an angle. even if it's a thousandth out on that bore, it will translate to a thousandth or more! out of square at the face of that receiver.

You could be doing damage by lapping that face.

EDIT:

After looking at these tools on line, I am going to go ahead and say that they are in fact TAKING THE FACE OUT OF SQUARE of the bore! The bore dimension for the extension is tighter than the dimension on the carrier bore. If you look at these tools, the pilot is inserted, and skips past the tightly held extension bore, and goes into the looser dimensioned carrier bore. So as this tool falls into the carrier bore, it is forcing the laping face out of square with the extension bore.

Ryan "
View Quote
Yep. I've never understood why someone wants to take an item that's been CNC machined, and try to hand lap it square. Even forged uppers and lowers are machined. It's something that was good in the 60's and 70's, but it's now passed its prime. Like people who still insist on lapping scopes and rings. Time to let go.
5/11/2017 7:36:09 AM EDT
[#38]
While I understand the technical argument when things are boiled down to the science of math and measurements.......but........experience is showing that home assemblers are resolving issues with rear sights that are getting cranked all the way to one side or another just to get a zero. I've said before- you would have to be awful careless or have a tool which is out of spec to ruin an upper from lapping. I don't see what it hurts. If you think it's snake oil- don't do it.
5/11/2017 10:44:15 AM EDT
[#39]
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While I understand the technical argument when things are boiled down to the science of math and measurements.......but........experience is showing that home assemblers are resolving issues with rear sights that are getting cranked all the way to one side or another just to get a zero. I've said before- you would have to be awful careless or have a tool which is out of spec to ruin an upper from lapping. I don't see what it hurts. If you think it's snake oil- don't do it.
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I don't think you do.

The precision of that tool is only going to be as precise as your eyeball, unless you can can see the differences in tolerances in the tenths of thousandths of inch. In this case we have two tolerances to be concerned about, a radial and a face to face. If one of them is not correct it completely negates the other. Putting that upper on a lathe and using a dial indicator to check the concentricity of both dimensions is the only correct way to do this properly.


That second part, why bother doing anything if you're not going to try and do it correctly?
5/11/2017 12:04:53 PM EDT
[#40]
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Quoted:
I don't think you do.

The precision of that tool is only going to be as precise as your eyeball, unless you can can see the differences in tolerances in the tenths of thousandths of inch. In this case we have two tolerances to be concerned about, a radial and a face to face. If one of them is not correct it completely negates the other. Putting that upper on a lathe and using a dial indicator to check the concentricity of both dimensions is the only correct way to do this properly.


That second part, why bother doing anything if you're not going to try and do it correctly?
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Quoted:
Quoted:
While I understand the technical argument when things are boiled down to the science of math and measurements.......but........experience is showing that home assemblers are resolving issues with rear sights that are getting cranked all the way to one side or another just to get a zero. I've said before- you would have to be awful careless or have a tool which is out of spec to ruin an upper from lapping. I don't see what it hurts. If you think it's snake oil- don't do it.
I don't think you do.

The precision of that tool is only going to be as precise as your eyeball, unless you can can see the differences in tolerances in the tenths of thousandths of inch. In this case we have two tolerances to be concerned about, a radial and a face to face. If one of them is not correct it completely negates the other. Putting that upper on a lathe and using a dial indicator to check the concentricity of both dimensions is the only correct way to do this properly.


That second part, why bother doing anything if you're not going to try and do it correctly?
I'll stand by what I said....and the purpose of the tool in my opinion is to bring the upper CLOSER to the spec, which it has proven itself to do. No, it won't do what a lathe and precision measuring instruments will do and I didn't say that.

Doing something correctly or "by the books" is always preferable. But sometimes the improvise-overcome-adapt mindset works too. I can't count how many times I've done a repair with a carbide burr in a die grinder and a welder- and it should have been done in a machine shop. But it worked....
5/11/2017 12:34:34 PM EDT
[#41]
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Quoted:

I'll stand by what I said....and the purpose of the tool in my opinion is to bring the upper CLOSER to the spec, which it has proven itself to do. No, it won't do what a lathe and precision measuring instruments will do and I didn't say that.

Doing something correctly or "by the books" is always preferable. But sometimes the improvise-overcome-adapt mindset works too. I can't count how many times I've done a repair with a carbide burr in a die grinder and a welder- and it should have been done in a machine shop. But it worked....
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Where might I find this "spec" and how was this proven?

Before you machine to any metal surface the very first thing that you need to know is how much metal needs to be removed, in this case its the concentricity the face of that upper followed by the inside diameter of the upper that your barrel is going to be mated to.

Without knowing any of that its quite possible that you have made the barrel/ receiver alignment even worse than it was.
5/11/2017 12:40:28 PM EDT
[#42]
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Yep. I've never understood why someone wants to take an item that's been CNC machined, and try to hand lap it square.
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Yep. I've never understood why someone wants to take an item that's been CNC machined, and try to hand lap it square.
To correct errors.  CNC =/= perfect.  Mistakes get through qc.



Like people who still insist on lapping scopes and rings. Time to let go.
Let go of what?  Scope rings can be way off.  And who is lapping scopes?
5/12/2017 4:02:04 PM EDT
[#43]
My intent when I had my uppers machined flat was to take away as many of the variables in regards to the rifle that I could. There are too many reviews concerning the commercially availiable lapping tools that I knew I may only make the situation worse. To me, it made more sense to spend the $10 per upper to have a machinist use the proper tool for the job and mill the face dead nuts flat. Both my uppers needed some material removed. Both were expensive billet and we're presumed to be totally in spec. Besides, after you buy the tool and do it, your always gonna ask yours if all you did was remove the anodizing or did you make the face flat?? Good luck all.
5/13/2017 11:13:07 AM EDT
[#44]
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Quoted:
Before lapping your upper, you might consider this feedback from 2A-Armament:

http://www.ar15.com/forums/t_2_493/269790_Do-I-need-to-lap-a-Balios-Lite-upper-.html

"One thing to consider, and BK already hit it in a more technical sense, is this....

If the lapping tool can fit down the bore, it means that it's sitting inside that bore at an angle. even if it's a thousandth out on that bore, it will translate to a thousandth or more! out of square at the face of that receiver.

You could be doing damage by lapping that face.

EDIT:

After looking at these tools on line, I am going to go ahead and say that they are in fact TAKING THE FACE OUT OF SQUARE of the bore! The bore dimension for the extension is tighter than the dimension on the carrier bore. If you look at these tools, the pilot is inserted, and skips past the tightly held extension bore, and goes into the looser dimensioned carrier bore. So as this tool falls into the carrier bore, it is forcing the laping face out of square with the extension bore.

Ryan "
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This is false. The receiver bore is the same diameter all the way thru. Don't believe me? Measure it, or insert the lapping tool in the rear of the receiver, its just as tight as the front. It's not going in the bore at an angle, the only thing not flush is the uneven receiver face. Should probably have some first hand experience with the tool before deciding whether it works or not. I've lapped way to many receivers for anyone to tell me it doesn't work, especially someone that's never used the tool.
I've lapped a few that were way off, like 15+ clicks of windage to get zeroed. After lapping, only 1 or 2 clicks if any.
Sometimes I don't remove all the anodizing. There's one important thing to check before lapping. You need to insert the barrel extension into receiver and look at the feed ramps to make sure there's a little bit of room for lapping. If you remove to much material during lapping, the ext feed ramps will hang over the receivers feed ramps. Should be very little to no set-back if done correctly. Always lube the shaft and inside of receiver before lapping. I have all 3 lapping tools mentioned in this thread, they all work just fine.

ETA: There's a great tutorial on here from one of our long time respected members but I can't find it at the moment.
5/31/2017 5:02:47 AM EDT
[#45]

9mm: no gas tube




5/31/2017 9:34:00 AM EDT
[#46]
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Odds are this is the best one on the market but I see now it is no longer a stocked item and "made to order".

PTG Lapping Tool

It's waaaay better than the Wheeler Engineering lapping tool and has to be better than the Brownells if theirs is soft.
PTG tool worked great for me.....

http://i77.photobucket.com/albums/j69/maximusscriptorius/95EA8434-A6EF-4FAF-875A-1C47F0C390CF_zpsaypsdk89.jpg
http://i77.photobucket.com/albums/j69/maximusscriptorius/117B3F24-CA9A-44DC-8CA5-70E8590D8017_zpsuamjcwkb.jpg
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This tool is back in stock at PTG. 
5/31/2017 8:21:00 PM EDT
[#47]
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These are excellent illustrations of "just enough" squaring/truing.  Some of your uppers were more irregular than others, requiring more work to square them.  But all of them have a bit of the anodizing still intact.  Not "milled back until it's all shiny," but with just enough coating/material removed for the face to be square and true.

Thanks for sharing your pictures!
6/1/2017 10:10:59 AM EDT
[#48]
I thought this thread died! Thank you to everyone that contributed.
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