"Accurizing the AR-15"

I've watched a few youtube videos on how Criterion recommends putting ARs together to optimize accuracy.

They talk about a bunch of stuff such as getting the optimal bolt for head space, thermal fit uppers, squaring up/lapping the upper receiver for the barrel extension, "bedding" the barrel using a sleeve retainer compound, the type of gas tube and how it needs to fit, etc. I am not even sure if they even cover everything - there could be more stuff. The nuances in these videos are pretty nuts.

I'm curious if anyone knows of any OEMs that actually assemble rifles like this. I'm assuming no as I don't see it in their marketing. Are there any high-end builders that do this if I ship them all the stuff?

Ultimately, what I am **think** I am asking is, if I wanted to get an ultra accurate AR-15, what are my options? / what is the best way to do it? / what is the easiest way to do it? Is it even worth the trouble?

If you are interested in the vids - here they are...They have a 4 part series that posted 6 years ago - this is part 1. https://www.youtube.com/watch?v=KF1vCYbaA0Q

There was also a guy who went there to get his rifle rebarreled that talked about the same thing. https://www.youtube.com/watch?v=TvWYzCGEuxo

Quote:

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Originally Posted by Cool Breeze

I've watched a few youtube videos on how Criterion recommends putting ARs together to optimize accuracy.

They talk about a bunch of stuff such as getting the optimal bolt for head space, thermal fit uppers, squaring up/lapping the upper receiver for the barrel extension, "bedding" the barrel using a sleeve retainer compound, the type of gas tube and how it needs to fit, etc. I am not even sure if they even cover everything - there could be more stuff. The nuances in these videos are pretty nuts.

I'm curious if anyone knows of any OEMs that actually assemble rifles like this. I'm assuming no as I don't see it in their marketing. Are there any high-end builders that do this if I ship them all the stuff?

Ultimately, what I am **think** I am asking is, if I wanted to get an ultra accurate AR-15, what are my options? / what is the best way to do it? / what is the easiest way to do it? Is it even worth the trouble?

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Myself, I don't think many manufacturer's would share their "secret tricks"... kinda like a NASCAR team sharing their secrets.

But I have applied many of Criterion's recommendations , and IMHO they do help.

This is 10rds, at 100yds, scoped, benched, bagged.. etc> PSA upper and lower, Criterion 22" 6.5CM , Hornady AG 140gr... various Criterion "Tricks" applied during assm., Yes , I blew the flier.

Attachment 110868


This group, is also same as above, but 308 18" Criterion barrel, 155gr Horn AG , same everything else.
Note I blew this flier as well...

Attachment 110869


IMHO, I would build / assemble one, if I can do it, anyone can.

Quote:

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Originally Posted by Cool Breeze

I'm curious if anyone knows of any OEMs that actually assemble rifles like this. I'm assuming no as I don't see it in their marketing. Are there any high-end builders that do this if I ship them all the stuff?

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If you want to buy this might actually be cheaper than buying your own and sending it off: https://www.whiteoakarmament.com/shop.html

(I have this one: https://www.whiteoakarmament.com/a4-...-ban-1751.html ) I've never shot it bagged at both ends, if it's warm enough tomorrow I might go out and do it.

WHITE OAK COMPETITION SERVICE & MATCH RIFLE UPPERS
The uppers on this page are John's recommended configurations. If you don't want to worry about selecting the right barrel and the right sight options simply choose one of these uppers and be assured you will have a winning configuration.

White Oak builds top quality uppers which have won many state, regional and national championships. Both the parts and the workmanship are held to the highest standards by competitive shooters who demand accuracy and reliability. With over 30 years of competitive experience White Oak knows high power competition. All uppers are built with the same components and techniques John uses in his own uppers. With your White Oak upper you can be confident that you are prepared to compete at any level.

From my brief foray into NRA High Power a decade ago, White Oak was my thought as well.

Quote:

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Originally Posted by Cool Breeze

squaring up/lapping the upper receiver for the barrel extension, "bedding" the barrel using a sleeve retainer compound

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Thanks for bringing this up, I have always contemplated doing these two steps, and I am getting ready to re-barrel one of my primary rifles and will probably do the lapping, and should also probably will do the glue.

Quote:

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Originally Posted by Cool Breeze

Is it even worth the trouble?

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I don't know, but both of the two things I would consider are cheap and look easy, and I am planning to tear it apart anyway, so I will probably do the experiment.

I think I still have my Brownells lapping tool from my years-ago foray into this rabbit hole if anyone wants to make an offer. I can toss in the sleeve-locking compound as well.

It's heavy, so shipping may be a factor.

Chris

I have a White Oak built upper and had a Fulton Armory built upper from my very brief foray returning into HiPower E class competition a few years ago. They are both sub moa with good ammo. I think both companies have some successful approach but I could not begin to tell you how they build them. I could not tell you one was better than the other because of my very limited skills. I suspect when they build the whole gun and not just the upper those are even better.

Has anyone ever seen a difference in lapping the upper?

I like BCM’s thermo fit uppers and have bedded barrels in looser fitting uppers before but I don’t buy into lapping.
First, I’ve not seen an upper not square enough to make contact all the way around yet.
Second, a loose fitting guide inside the upper is subject to cutting off center when done by hand.
Third, I don’t like to remove anodizing.

I’ve seen a few attempts trying to prove it does work only to not make any difference. But it would be hard to see any improvement until 300 yards or so anyway. Just wondering if this has been proven or just something else to sell.

The only tips I’ve got is to start with a good barrel, limit barrel nut torque to 40’ lbs. Just snug the muzzle device after loctite has been applied. I have swapped a bolt once that passed a field gauge but accuracy did improve with another bolt.

I have lapped a couple uppers, and noted that the face was slightly off-square before the correction. I can't say it was helpful because I didn't do before/after testing. If you have the lapper that runs through the receiver, the tight BCM uppers can't be lapped.

That being said. I have a couple Criterion CORE barrelled uppers and they seem to be very accurate with cheap ammo like XM193. I can't ask for more

Quote:

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Originally Posted by mmc45414

Thanks for bringing this up, I have always contemplated doing these two steps, and I am getting ready to re-barrel one of my primary rifles and will probably do the lapping, and should also probably will do the glue.


I don't know, but both of the two things I would consider are cheap and look easy, and I am planning to tear it apart anyway, so I will probably do the experiment.

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I am a true believer in the "True n' Glue".

FWIW, the various lapping tool's , I have tried, have certain uppers they worked well with.

Brownells, thermal fit uppers like BCM
PTG , used to work well with non-thermal fit uppers.. I say used to , because they sell to different sizes now.
The Caldwell ( cheap ) lapping tool, was such a poor fit, I could see doing more damage than good.

I also do not place the upper in a vice, while lapping. I turn the upper vertical and use a low speed setting cordless drill. That way I can feel any "odd" binding. Be sure to lube the lapping tools shaft.

FWIW... and while far from scientific, here is a PSA 20" OEM barrel 6.5CM before and after TnG ( True and Glue ). The thread is a little choppy.... but I don't write for a living. Lol
Not every factory load responded well to the TnG, but... many did group far better after.

And the odd ball fliers seemed to occur less often.

Enjoy the read...

https://www.ar15.com/forums/industry...s-/301-285762/

I've never tried any of it but d. Wilson does offer bedding/shimming and receiver truing services.

I've adopted this method of building my uppers, but instead of using retaining compound I use stainless steel shim stock to tighten the fit of the barrel extension into the upper. If I were building a new upper today, I'd spend the money on a VLTOR MUR, BCM, or Sons upper receiver that would allow the thermal fit method. I also true the receiver with a lapping tool.
In my experience, lapping the receiver will minimize the windage adjustment on the optic or irons when zeroing. If you have an upper where you have to make an extreme windage adjustment on the rear BUIS, lapping the receiver might be the ticket for you.
I did witness firsthand an accuracy increase from tightening up the barrel extension fit to the receiver. My main and favorite AR is a BCM 16" upper with a cold hammer forged barrel purchased around 2012, before BCM adopted their thermal fit specs and were just making Milspec upper receivers. I was getting around 3 MOA accuracy with M193 ammo on this upper. As time went on and I got deeper into the hobby of putting these things together, I wanted to change the handguard out and had read about the different ways to "accurize" the AR. When I took it apart, the fit was akin to a hotdog in a hallway. I lapped the receiver with a wheeler tool and used 0.003 stainless shim stock to achieve a really tight fit of the extension. This rifle now shoots M193 1.5 to 2 MOA, and shoots Speer Gold Dot LE 62 GR .223 sub-MOA. I don't think a huge increase like this is typical, and some of that very well could be me being a better shooter now than when I first started out. I'm a full on nerd about zeroing and get the rifle really stable using bags now.

Quote:

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Originally Posted by stomridertx

I've adopted this method of building my uppers, but instead of using retaining compound I use stainless steel shim stock to tighten the fit of the barrel extension into the upper. If I were building a new upper today, I'd spend the money on a VLTOR MUR, BCM, or Sons upper receiver that would allow the thermal fit method. I also true the receiver with a lapping tool.
In my experience, lapping the receiver will minimize the windage adjustment on the optic or irons when zeroing. If you have an upper where you have to make an extreme windage adjustment on the rear BUIS, lapping the receiver might be the ticket for you.
I did witness firsthand an accuracy increase from tightening up the barrel extension fit to the receiver. My main and favorite AR is a BCM 16" upper with a cold hammer forged barrel purchased around 2012, before BCM adopted their thermal fit specs and were just making Milspec upper receivers. I was getting around 3 MOA accuracy with M193 ammo on this upper. As time went on and I got deeper into the hobby of putting these things together, I wanted to change the handguard out and had read about the different ways to "accurize" the AR. When I took it apart, the fit was akin to a hotdog in a hallway. I lapped the receiver with a wheeler tool and used 0.003 stainless shim stock to achieve a really tight fit of the extension. This rifle now shoots M193 1.5 to 2 MOA, and shoots Speer Gold Dot LE 62 GR .223 sub-MOA. I don't think a huge increase like this is typical, and some of that very well could be me being a better shooter now than when I first started out. I'm a full on nerd about zeroing and get the rifle really stable using bags now.

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FWIW... the SOLGW upper is also a MUCH snugger fit on every lower I tried.
IMHO a tight fit between the upper and lower makes it far easier to wield the AR more consistently.

BCM lower was TIGHT. As in had to "slap" the 2 parts apart.
Colt was inbetween TIGHT and snug.
SanTan lower was snug.
Rainer Arms lower was snug.
PSA was a much better fit, compared to PSA uppers.

I tried the SOLGW upper on other make lowers, but I don't remember which ones.

Quote:

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Originally Posted by stomridertx

I also true the receiver with a lapping tool. In my experience, lapping the receiver will minimize the windage adjustment on the optic or irons when zeroing. If you have an upper where you have to make an extreme windage adjustment on the rear BUIS, lapping the receiver might be the ticket for you.

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I use a Brownell's lapping tool and have noticed the same thing which I thought was the whole point of lapping.

I pretty much use nothing but BCM blem uppers. I tend to use Green Mountain Barrels when they have what I want, but have also used others. Fit to receiver is snug, but I've never had to thermal fit. Is that unique to the blem uppers?

Quote:

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Originally Posted by Dan Lehr

I use a Brownell's lapping tool and have noticed the same thing which I thought was the whole point of lapping.

I pretty much use nothing but BCM blem uppers. I tend to use Green Mountain Barrels when they have what I want, but have also used others. Fit to receiver is snug, but I've never had to thermal fit. Is that unique to the blem uppers?

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Making the barrel stick out of the receiver as straight as possible to fix extreme windage adjustments is the whole point of lapping. I pointed it out to answer TWR's question earlier as I think the original intent of it seems to have been lost over time and has deteriorated to:
"Dude, you should totally lap your receiver!"
"Why?"
"Cuz accuracy bro!"
It's honestly probably not worth the time on an upper that isn't getting a rear iron sight. Scopes and red dots have plenty of adjustment and windage doesn't get dialed to the same degree as elevation. I was able to fix a friend's retro AR build with lapping though as his carry handle rear sight adjustment was damn near all the way to the left and he hated it. Lapping moved it close to center on zero. As armorer level tasks go, lapping is easy.

Nearly every off center rear sight that I’ve seen, in person and on the wild wild net, has been to the left. Before the lap tool became popular, it was a hammer to the front sight base that rotated the sight back in line. Seems odd that the rear was always to the left. Never bothered elevation either.

I have a cheap upper that The rear sight is to the left. I thought about this when it was mentioned lapping fixes the issue. After closer examination, my rail is canted. I’m gonna buy a lap and try it but I’m still not understanding how a hand held tool can be the cure when I go to rather great extremes to square things up on my lathe. I’ll give it a try but first I will see if the upper is square to begin with.

Please don’t take this as arguing, my mind just works this way.

We have a BCM ELW-F 14.5” with the original Magnesium KMR rail that I purchased used about 7-8 years ago. It’s a great gun but I’ve zeroed it with two different sets of iron sights and the rear is always pretty far to the left. It shoots just fine but I never thought about the upper not being square, causing the barrel to actually be tilted.

Quote:

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Originally Posted by TWR

Nearly every off center rear sight that I’ve seen, in person and on the wild wild net, has been to the left. Before the lap tool became popular, it was a hammer to the front sight base that rotated the sight back in line. Seems odd that the rear was always to the left. Never bothered elevation either.

I have a cheap upper that The rear sight is to the left. I thought about this when it was mentioned lapping fixes the issue. After closer examination, my rail is canted. I’m gonna buy a lap and try it but I’m still not understanding how a hand held tool can be the cure when I go to rather great extremes to square things up on my lathe. I’ll give it a try but first I will see if the upper is square to begin with.

Please don’t take this as arguing, my mind just works this way.

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I don't think the receivers are actually out of spec when the barrel isn't perfectly straight if it's a quality manufacturer, it's the anodizing that gets applied a tiny bit uneven and the lapping tool just evens it out. I saw a video of someone truing a receiver with a lathe and there's no doubt that is a superior way to do it if you have the machine and the skills to use it.
The reason I only point out windage is that the elevation adjustment of a front sight isn't visually annoying like the rear sight is. If you have to go a little farther up or down because of the barrel, the front sight doesn't look different in the sight picture. If the rear aperture is extreme left or right, it can really grind your gears to look at even though the rifle may be zeroed just fine. You are correct that the FSB can be canted and that can be the culprit more than how the barrel sits in the receiver, but on the rifle I mentioned that was not the case.
The way I view lapping is that it's easy to do and if I have the upper taken apart anyway, might as well true it up. I wouldn't take apart an upper just to lap it unless it had the iron sight windage adjustment problem, or it had poor accuracy in general and I mainly wanted to fit the barrel to the receiver better. If I had a newer BCM receiver that my lapping tool wouldn't fit in, it wouldn't bother me as I really don't use irons much anymore unless it's a rifle getting a red dot as a primary optic.

Yeah it’s one of those things that doesn’t really hurt a thing if done right.

On the rifle I’m fixing to redo I noticed the anti rotation tab on the left side is against the upper while the right side has a slight gap. I install my rails with a one piece scope mount bridging the upper and rail. That way it should line the 1913 pic slots up. But this one didn’t for some reason. It is my old truck gun that I put together with extra parts and a buddy gave me the barrel. I had Daniel Defense fixed irons on it with a red dot. Never noticed the rear sight to the left but when I swapped the DD’s out for Troy folders, it’s very noticeable.

I just always assumed the rear sight to the left was because the barrel twisted a bit when torqued. But now with front sights on rails, it makes me rethink all this.

After zeroing the gun this morning with the new Troy sights and no red dot on the gun, it is but a smidge to the left. I know better than to try and zero them to the dot, shooting is the only way.

It also shot good enough at 200 with my 1-4 Trijicon that a better barrel is not needed but Black Friday deals might talk me into it anyway. But for now I have a red dot, irons and a scope zeroed and really killed my desire to take it back apart.

Quote:

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Originally Posted by bfoosh006

Myself, I don't think many manufacturer's would share their "secret tricks"... kinda like a NASCAR team sharing their secrets.

But I have applied many of Criterion's recommendations , and IMHO they do help.

This is 10rds, at 100yds, scoped, benched, bagged.. etc> PSA upper and lower, Criterion 22" 6.5CM , Hornady AG 140gr... various Criterion "Tricks" applied during assm., Yes , I blew the flier.

Attachment 110868


This group, is also same as above, but 308 18" Criterion barrel, 155gr Horn AG , same everything else.
Note I blew this flier as well...

Attachment 110869


IMHO, I would build / assemble one, if I can do it, anyone can.

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Great shooting!

Quote:

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Originally Posted by TWR

Has anyone ever seen a difference in lapping the upper?

I like BCM’s thermo fit uppers and have bedded barrels in looser fitting uppers before but I don’t buy into lapping.
First, I’ve not seen an upper not square enough to make contact all the way around yet.
Second, a loose fitting guide inside the upper is subject to cutting off center when done by hand.
Third, I don’t like to remove anodizing.

I’ve seen a few attempts trying to prove it does work only to not make any difference. But it would be hard to see any improvement until 300 yards or so anyway. Just wondering if this has been proven or just something else to sell.

The only tips I’ve got is to start with a good barrel, limit barrel nut torque to 40’ lbs. Just snug the muzzle device after loctite has been applied. I have swapped a bolt once that passed a field gauge but accuracy did improve with another bolt.

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The lapping (via the brownells tool method is the one I'm most skeptical about for the reasons you mentioned as well as me wondering if a $30 tool is really "more square/precise" than what is done by the machining of a good quality upper. If done on a lathe, that might be a different story.

Quote:

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Originally Posted by Wake27

I've never tried any of it but d. Wilson does offer bedding/shimming and receiver truing services.

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I didn't realize he did this. Thank you! That may be the easy button for me if I don't feel like getting all the tools to do this myself.

Quote:

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Originally Posted by bfoosh006

FWIW... the SOLGW upper is also a MUCH snugger fit on every lower I tried.
IMHO a tight fit between the upper and lower makes it far easier to wield the AR more consistently.

BCM lower was TIGHT. As in had to "slap" the 2 parts apart.
Colt was inbetween TIGHT and snug.
SanTan lower was snug.
Rainer Arms lower was snug.
PSA was a much better fit, compared to PSA uppers.

I tried the SOLGW upper on other make lowers, but I don't remember which ones.

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Interesting - I had a somewhat different experience. I have Triarc matching serial set and its TIGHT. My SOLGW uppers and lowers can move ever so slightly but not noticable unless you try to move it - its not as tight as what is on their youtube video though. A BCM Mk2 upper and BCM lower was the looses of the group. That being said, I like the BCM Mk2 upper being that its thermal fit and the "newer" design. I am not sure if SOLGW is considered thermal fit as the youtube video says undersized and then he hammers it in with a mallet. Maybe that means the same thing as thermal fit?

Quote:

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Originally Posted by Dan Lehr

I use a Brownell's lapping tool and have noticed the same thing which I thought was the whole point of lapping.

I pretty much use nothing but BCM blem uppers. I tend to use Green Mountain Barrels when they have what I want, but have also used others. Fit to receiver is snug, but I've never had to thermal fit. Is that unique to the blem uppers?

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Are you using mk2 uppers or mk1? I've only heard the mk2 being referred to as thermal fit but that is not to say the mk1 uppers are not.

Quote:

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Originally Posted by Cool Breeze

The lapping (via the brownells tool method is the one I'm most skeptical about for the reasons you mentioned as well as me wondering if a $30 tool is really "more square/precise" than what is done by the machining of a good quality upper. If done on a lathe, that might be a different story.

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IMO/E making something like that tool is simple, cheap, and on a modern CNC it will be accurate. And if you just want the ID to be in perpendicular alignment with the front face of the receiver this sure seems like a straightforward approach.

Reading this thread over on SH seems to indicate the glue (or shim) might be more important than the facing, since the barrel extension is just a slip fit anyway. But the facing might clean up any variation in the anodize. There was also thought that it might help square up the bolt lugs, but that would just be gravy.

So my take on this is that there are probably not big enough gains (for me) to bother paying a professional (and UPS, twice) to fixture it up in a lathe and then measure for and cut and install a shim. I would probably not take an upper apart just to do this, but I am getting ready to do four uppers I plan to buy the tool and the glue. It will only add ~$10 each, just seems like it is too easy and cheap of an opportunity to skip, even if it actually nets me nothing.

Years ago I went through the process of accurizing my Sionics upper:

• lapping the receiver face
• free floating gas tube
• shimming and gluing barrel to receiver

I did it all at once so I don't know which ones made the difference.

My testing before and after showed that good loads didn't really improve significantly but some of my previously "bad" loads got a lot better.

To put it another way, the changes didn't raise the ceiling for my accuracy potential, but it did raise the floor on what I could expect when shooting commercial ammo.

Quote:

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Originally Posted by Cool Breeze

Are you using mk2 uppers or mk1? I've only heard the mk2 being referred to as thermal fit but that is not to say the mk1 uppers are not.

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These are the ones I've been using:

BCM® M4 Flat Top Upper Receiver with cosmetic blemishes. Most have scratches or scuffs.

The upper comes unassembled, but complete with BCM forward assist assembly and ejection port cover door assembly.
You must assemble it. (Assembly required) (all parts, but you will have to assemble together)

THESE ARE USED/DEMO UPPER RECEIVER ASSEMBLIES. All will have several nicks, scratches, and marks on exterior finish. NO HANDPICKING.

This receiver has the M4 feedramps machined in. This is to be used with barrels that include the M4 barrel extension.

Built to the correct Mil-Specs.
(Inside Diameter for barrel extension slightly undersized for a tighter fit to the barrel and a more accurate rifle. Please use a heat gun or hair dryer to warm up threaded bore of receiver if barrel extension is too tight.)

I bought a Mk2 when they first came out, but didn't need to heat it either. Do they even make them anymore?

Quote:

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Originally Posted by mmc45414

IMO/E making something like that tool is simple, cheap, and on a modern CNC it will be accurate. And if you just want the ID to be in perpendicular alignment with the front face of the receiver this sure seems like a straightforward approach.

Reading this thread over on SH seems to indicate the glue (or shim) might be more important than the facing, since the barrel extension is just a slip fit anyway. But the facing might clean up any variation in the anodize. There was also thought that it might help square up the bolt lugs, but that would just be gravy.

So my take on this is that there are probably not big enough gains (for me) to bother paying a professional (and UPS, twice) to fixture it up in a lathe and then measure for and cut and install a shim. I would probably not take an upper apart just to do this, but I am getting ready to do four uppers I plan to buy the tool and the glue. It will only add ~$10 each, just seems like it is too easy and cheap of an opportunity to skip, even if it actually nets me nothing.

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That makes perfect sense to me. Nice thread link btw - interesting read.

Quote:

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Originally Posted by Dan Lehr

These are the ones I've been using:

BCM® M4 Flat Top Upper Receiver with cosmetic blemishes. Most have scratches or scuffs.

The upper comes unassembled, but complete with BCM forward assist assembly and ejection port cover door assembly.
You must assemble it. (Assembly required) (all parts, but you will have to assemble together)

THESE ARE USED/DEMO UPPER RECEIVER ASSEMBLIES. All will have several nicks, scratches, and marks on exterior finish. NO HANDPICKING.

This receiver has the M4 feedramps machined in. This is to be used with barrels that include the M4 barrel extension.

Built to the correct Mil-Specs.
(Inside Diameter for barrel extension slightly undersized for a tighter fit to the barrel and a more accurate rifle. Please use a heat gun or hair dryer to warm up threaded bore of receiver if barrel extension is too tight.)

I bought a Mk2 when they first came out, but didn't need to heat it either. Do they even make them anymore?

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Great question - When I looked a bit ago, I didn't see them on their site as being sold separately but that was just a cursory glance.

Crap!!!!
People must have been reading this thread...

Attachment 111134

Quote:

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Originally Posted by Dan Lehr

These are the ones I've been using:

BCM® M4 Flat Top Upper Receiver with cosmetic blemishes. Most have scratches or scuffs.

The upper comes unassembled, but complete with BCM forward assist assembly and ejection port cover door assembly.
You must assemble it. (Assembly required) (all parts, but you will have to assemble together)

THESE ARE USED/DEMO UPPER RECEIVER ASSEMBLIES. All will have several nicks, scratches, and marks on exterior finish. NO HANDPICKING.

This receiver has the M4 feedramps machined in. This is to be used with barrels that include the M4 barrel extension.

Built to the correct Mil-Specs.
(Inside Diameter for barrel extension slightly undersized for a tighter fit to the barrel and a more accurate rifle. Please use a heat gun or hair dryer to warm up threaded bore of receiver if barrel extension is too tight.)

I bought a Mk2 when they first came out, but didn't need to heat it either. Do they even make them anymore?

---

Quote:

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Originally Posted by Cool Breeze

Great question - When I looked a bit ago, I didn't see them on their site as being sold separately but that was just a cursory glance.

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I missed the edit window on my post.

I recently bought a couple more blem uppers because I only had one left. I hadn't opened the box yet and just did so. Both uppers had a slip of paper in them explaining how to thermal fit the barrel extension. That was a first, never received those in an upper before.

If you look at the first picture where the upper contacts the lower by the receiver extension, the 'web' at the bottom looks thicker than the web at the bottom of the second picture. Maybe it's just because it's joined to a lower, IDK. No big deal, just looked unusual.

Quote:

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Originally Posted by Cool Breeze

Great shooting!

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Sometimes... I can getter done, Lol

Quote:

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Originally Posted by Cool Breeze

The lapping (via the brownells tool method is the one I'm most skeptical about for the reasons you mentioned as well as me wondering if a $30 tool is really "more square/precise" than what is done by the machining of a good quality upper. If done on a lathe, that might be a different story.

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FWIW... I suspect the Anodizing is the part that isn't even... not the CNC machine work.

I spoke to guys that anodize for a living and they said anodizing can easily be applied un evenly... ( IE thicker or thinner, and even dependent on the positioning in the tank )

As for the precision of the lapping tools, and I don't know if I mentioned it before, this video shows a Wheeler tool being used... My wheeler tool is crap. A VERY sloppy fit. I actually now use it to lap the insides of buffer tubes smooth.

FWIW..I also don't like to use a vice to hold the upper. I prefer to hand hold the upper, vertically with the drill and lapping tool on the bottom.

I watched a major manufacturer's worker lapping a upper, with it in a vise... and man, he was lapping like he was putting lug nuts on a semi, fully pounding the lug nuts home, with a air impact gun. Lol, not sure I will ever forget that.

My OCD makes me think a vise "could" produce unwanted binding, or maybe better said unnoticed binding.

And...the shank on a good fitting tool will burnish smooth the uppers "raceway" the BCG rides in. DO NOT USE Lapping compound inside the lower, oil will be fine.


I DON"T use the Wheeler Tool... it just seems very poorly sized. Watch this video.

https://www.youtube.com/watch?v=UGB61f4zznk


A good video...Criterion's Video 3 showing the lapping with a Brownells tool... about the 55 second mark.

https://www.youtube.com/watch?v=XHxU8VUAHOY&list=UULFB4LHYkqZB83mSUdSH NJHm Q&index=10

The other thing that makes me see snake oil is the fact that the bolt locks up in the barrel extension. There’s plenty of room between the bolt and the carrier and lots of room between the carrier and the upper that “trueing” the face of the upper can’t make any difference like lapping the bolt of a bolt action gun.

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Originally Posted by TWR

The other thing that makes me see snake oil is the fact that the bolt locks up in the barrel extension. There’s plenty of room between the bolt and the carrier and lots of room between the carrier and the upper that “trueing” the face of the upper can’t make any difference like lapping the bolt of a bolt action gun.

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We don't have to be suspicious of this, it's a proven process vetted by Brownells selling all the lapping tools they make. I've seen the change in windage adjustment of a rear sight with my own eyes on more than one gun. If you are skeptical that lapping increases accuracy, you are right in that it doesn't. It just evens out the anodizing on the receiver face so the barrel sticks out of the receiver in a straight line. If the barrel is almost perfectly in line with the pic rail, then the windage adjustment of the sighting system will be more about the ammo used than mechanical alignment.