Beleiver in AR lapping

[bfoosh006]

Why does lapping the receiver face not affect head space? It seems like the barrel is being set back. Just wondering.

Actually the whole barrel and receiver extension are for all intents , "one piece"... and the bolt will seat with in that whole piece.

So a few thousands ( if that ) isn't going to adversely effect the bolts function at all.

If the barrel ( itself, no receiver extension, the RE controls the headspace in a round about fashion ) was screwed into the receiver / mounted to the upper... then headspace would be effected.

 

[hitman]

I did not expect this much info and input but it is awesome. A lot of solid thoughts. For me I cannot see the downside to doing it. It literally takes less than 5 mins and the tool was $ 30. I have done two so far. I just put one together this week with a 14.5" Crtiterion stainless barrel from Craddock on an Aero upper. The Aero's seem to need it a decent amount. I did not feel like doing a before and after project to see the difference. It should be a shooter though and easy to do.

 

[aslrookie]

Would applying the loktite be enough to shrink groups or do you need to true the face too? My Faxon barrel fits good, just a little slop in the extension but it takes some work to wiggle it out of the receiver.

 

[Yondering]

Would applying the loktite be enough to shrink groups or do you need to true the face too? My Faxon barrel fits good, just a little slop in the extension but it takes some work to wiggle it out of the receiver.

If you can feel some slop, the effort you're putting in to wiggle it out of the receiver is probably just a tight fit of the barrel extension pin in the slot, which does nothing for keeping the barrel extension true to the receiver. You'll need to shim or bond the barrel extension into the upper to eliminate the slop.

As we keep repeating - truing the receiver face is to ensure full bolt lug contact. Some of you guys keep asking if you have to do it for accuracy - no you do not, but it will help your gun live longer.

 

[Yondering]

I did not expect this much info and input but it is awesome. A lot of solid thoughts. For me I cannot see the downside to doing it. It literally takes less than 5 mins and the tool was $ 30. I have done two so far. I just put one together this week with a 14.5" Crtiterion stainless barrel from Craddock on an Aero upper. The Aero's seem to need it a decent amount. I did not feel like doing a before and after project to see the difference. It should be a shooter though and easy to do.

Yes, as you said it's pretty easy and there's no real reason not to do it. The naysayers mostly seem to be the guys who just don't want to buy the tools.

I did a couple PSA uppers tonight for a friend - one of them didn't need lapping at all (it showed full contact as soon as we started lapping) and the other needed it a lot with several iterations of clean, check, and lap some more until it was square.

 

[triumph001]

Any difference in the tools? Prices seem to range from about $25-$35. Some with some w/o lapping paste.
PTG is out, Wheeler, GG, Brownells, or others?

I recently bought x-caliber’s BART 2.0, they had a sale on the small and large frame combo pack around Christmas. Used them both in the last 2 weeks, both lapped my uppers flawlwssly. They are more expensive than some others but with the reaction rod on the other end it was worth it. I had never used a reaction rod and they are awesome. I had a gas tube issue to address and it was so nice to be able to flip that bitch over in about 1 second and loosen the set screw to remove the block, tweak and repeat. It still tested my patience but I imagine that if I had been using the clamshell or upper mounting block to hold it in the vise I would have been using the cuss bucket. They also have a version without the reaction rod.

X-Caliber - Accessories Page

X-Caliber Barrel & Manufacturing is the next generation for precision barrel manufacturing.

www.x-caliber.net

 

[FishinGuns]

Do you guys know of any one that trues Seekins uppers?

iRMT-R Upper

<p><strong>IRMT-R Upper</strong></p> <p>Seekins Precision’s Integrated Rail Mounting technology (iRMT) uppers integrate the rail mounting points into the upper receiver. This retains the stiffness while allowing the rails to

www.seekinsprecision.com

I have two of these for hunting builds I’m about to start, as soon as I decide on glass for each (20” .223 Wylde and 20” 6.5 Grendel Proof Research Carbon Fiber tubes going in each one).

If it can be done, I’d like to just do it now.

 

[BlackdogGS]

I just bought the Brownells lapping tool. I didn’t want to pay $36 for the lapping compound though. I see a few of you are using the valve lapping stuff from an auto parts store. What grit do you recommend?

 

[Yondering]

Use the fine grit. Mine just was labeled "coarse" and "fine", but the fine appears to be approximately 400 grit.

 

[Sogan]

I just bought the Brownells lapping tool. I didn’t want to pay $36 for the lapping compound though. I see a few of you are using the valve lapping stuff from an auto parts store. What grit do you recommend?

Wheeler 600 grit can be bought on amazon. Not sure what everyone prefers tho

 

[triumph001]

I just bought the Brownells lapping tool. I didn’t want to pay $36 for the lapping compound though. I see a few of you are using the valve lapping stuff from an auto parts store. What grit do you recommend?

The instruction pdf you can find on brownells lapping tool page say 180 grit.

 

[Spblademaker]

wheeler kit came with 220. Can’t see a need for anything more coarse. 320 would be perfect, I think.

 

[Ravenous]

Does anyone actually have quantifiable evidence that this does anything? While I agree that there's going to be differences between uppers/lowers especially with all the choices out there. I have yet to see one verifiable piece of evidence that shows this is worth it. Granted it's about 5 minutes of work but still. People will rarely admit that something was a waste of time or money when it's their hard earned money. I have built countless AR10s that are all under MOA. Most have been with using cheap Aero kits. Numerous different tests were done to check if we could squeeze more accuracy from rifle to rifle using small modifications like this but found little to no difference in the long run. I'm all for squeezing every bit of performance out of something but also feel there's a point of diminishing returns and perhaps the efforts should be focused elsewhere. Just because you feel better about performing the process doesn't mean it actually did anything. Just curious if someone actually took the time to document between stock vs lapped receivers, which could be a great baseline for everyone moving forward.

 

[Snuby642]

I'm gusessing you did not read the entire thread?
There was a before and after post on the lapping results.

A 30$ tool and 5 minutes of time and never having tried it you scoff at it, wow!
Many people would gladly give a 100$ bill for every 1/4 moa they can get.

 

[Spblademaker]

But there’s so many word things.....

 

[Eoddave27]

Does anyone actually have quantifiable evidence that this does anything? While I agree that there's going to be differences between uppers/lowers especially with all the choices out there. I have yet to see one verifiable piece of evidence that shows this is worth it. Granted it's about 5 minutes of work but still. People will rarely admit that something was a waste of time or money when it's their hard earned money. I have built countless AR10s that are all under MOA. Most have been with using cheap Aero kits. Numerous different tests were done to check if we could squeeze more accuracy from rifle to rifle using small modifications like this but found little to no difference in the long run. I'm all for squeezing every bit of performance out of something but also feel there's a point of diminishing returns and perhaps the efforts should be focused elsewhere. Just because you feel better about performing the process doesn't mean it actually did anything. Just curious if someone actually took the time to document between stock vs lapped receivers, which could be a great baseline for everyone moving forward.

After talking to a friend of mine who is a gunsmith about how to squeeze a little more accuracy out of my AR’s I went through and did all of mine (3 at the time). I made a jig that holds my receiver in a lathe and I face the receiver that way. After that I used Loctite 620 to bed the barrels. The group size on all the rifles decreased substantially with the loads developed for each with 5 shot groups. This brought all of them to around .5moa. This isn’t uncommon though. If you do a google search you will see quite a few other people who did before and after tests with similar results. I did notice that the results many got were not uniforms over all types of ammo though. I was also told by the gunsmith who recommended the method to me that he was taught this by the Smiths from the Army Marksmanship unit. At any rate based on my past experience this is an easy way to squeeze a little more accuracy out of your rifle and only takes a few minutes.

 

[Snuby642]

Last check Brownells and midway were sold out for ar 15 lappers.
Guess that is a hint?

Duh.

 

[Rocketvapor]

Midway is in stock

Wheeler Delta Series Upper Receiver Lapping Tool AR-15

The Wheeler Engineering AR-15 Receiver Lapping Tool allows the builder to true the surface of an AR-15 Upper Receiver to ensure a square surface for the...

www.midwayusa.com

Buds is in stock

Wheeler Delta AR-15 Receiver Lapping Tool

Use with a battery powered or electric drill to square the receiver face on an AR-15. Helps align the gas tube through the barrel nut holes. Helps align front and rear A2 style sights. Includes Flex d

www.budsgunshop.com

AR10

Wheeler Delta Series Upper Receiver Lapping Tool LR-308

Eliminate a factor of inaccuracy with the Wheeler AR LR/10 Variant Receiver Lapping Tool. A perfect fit of the receiver to the barrel is vital when it...

www.midwayusa.com

PAS DELTA AR LR/10 VAR LAP TOL

This steel-constructed tool, along with the provided 220 grit lapping compound, will make lapping quick and easy, to ensure a perfectly square and true surface to help you achieve an accurate, high pe

www.budsgunshop.com

 

[Rocketvapor]

Have you noticed that about ALL of them have a deep and long relief cut so some dummy doesn't get grit into the receiver? Or spin it up without lube and gall the inside of the receiver?

If someone would make one with a shorter relief cut that would also ride the inside of the receiver (with lube of course) it might even be better.
and,
the drill thing.
How many revolutions before the lapping compound has moved out of the contact area and isn't doing what you want? 2? Then you lift and do 2 more?
Drill?


We are on page 4, keep it going

 

[Mike_in_FL]

My only question on the subject is, when did people start talking about doing this? I want to say this became a step in building when folks kept having problems with 6.5 Grendel bolts?

I don't remember anybody talking about this until then.

 

[bobke]

While I cannot definitively say lapping was the reason why, have built a half dozen or so AR’s that all exhibit realistic 3/4” potential, most often better. All built with premium components, as well.
I liken the lapping process to truing your bolt gun receivers, or blueprinting an engine. Does the act assure accuracy in itself? Maybe/maybe not. You do it to take one more variable out of the equation to insure you’re doing everything possible to get to the goal. Just my take, but I’ll do it on every build just to confirm dimensions.

 

[Back Spin]

Hi @Eoddave27

What was the approximate accuracy of the guns prior to lapping and bedding?

 

[Ravenous]

I'm gusessing you did not read the entire thread?
There was a before and after post on the lapping results.

A 30$ tool and 5 minutes of time and never having tried it you scoff at it, wow!
Many people would gladly give a 100$ bill for every 1/4 moa they can get.

Actually I did read the entire thread, 75% was people arguing about what mil-spec means and what/how to headspace an AR properly. I saw one post by EODdave with posted results. I will say the results he achieved are extremely impressive but that is hardly quantifiable. There were many people that are performing this just based off of hearsay. I certainly don't disagree with you that for $30 and a couple minutes of time it's worth it, if it is a proven method. I'm actually curious to perform this and tear down my 308 to see if it increases the 1/2MOA accuracy I'm getting out of it. I'm just curious if anyone else has actual before/after results they can post. Stating that people are seeing under MOA with lapping isn't proving it works, the gun may have already been shooting that before the lapping process.

After talking to a friend of mine who is a gunsmith about how to squeeze a little more accuracy out of my AR’s I went through and did all of mine (3 at the time). I made a jig that holds my receiver in a lathe and I face the receiver that way. After that I used Loctite 620 to bed the barrels. The group size on all the rifles decreased substantially with the loads developed for each with 5 shot groups. This brought all of them to around .5moa. This isn’t uncommon though. If you do a google search you will see quite a few other people who did before and after tests with similar results. I did notice that the results many got were not uniforms over all types of ammo though. I was also told by the gunsmith who recommended the method to me that he was taught this by the Smiths from the Army Marksmanship unit. At any rate based on my past experience this is an easy way to squeeze a little more accuracy out of your rifle and only takes a few minutes.

I'm going to google around to see the results like you are talking about. I'd say achieving .75MOA difference like you mentioned previously is a huge gain, especially for the cost/time of doing this. My interest is certainly peaked, I'll have to go the poor mans way though since I don't have access to a lathe. I'll probably end up doing a before and after with my 6.5 that I'm about to finish up.

 

[Constructor]

While I cannot definitively say lapping was the reason why, have built a half dozen or so AR’s that all exhibit realistic 3/4” potential, most often better. All built with premium components, as well.
I liken the lapping process to truing your bolt gun receivers, or blueprinting an engine. Does the act assure accuracy in itself? Maybe/maybe not. You do it to take one more variable out of the equation to insure you’re doing everything possible to get to the goal. Just my take, but I’ll do it on every build just to confirm dimensions.

Exactly it's like the difference between a shadetree mechanic and a precision engine shop. High power shooters/smiths have ben doing it since the late 80s.
If the receiver is tight enough that the extension must be tapped into place it will not make much difference because the ID of the receiver and OD of the extension hold the barrel and lugs in line with the receiver bore.
The other part of it is a rigid connection. The receiver is the connection between the scope and the barrel.

 

[bfoosh006]

Here is my results with a PSA PA65... it isn't a definitive test.. but it is enough for me to start doing it to all my uppers large and small.

In a nut shell... it resulted in much smaller groups compared to before.


"Some of the rounds that showed the most improvement are ... ( no specific order.. ) Again group size does not have .264 subtracted from them.

Difference in group size, FGMM 130gr Hybrid OTM..... Before 2.3660" 5rds, .... After .9580".

Difference in group size, .Hornady 140gr ELD Match.... Before 2.2045" 5rds, .... After .9290".

Difference in group size, PRIME 130gr HPBT Match.... Before 1.9165" 5rds, .... After .9620"...

Difference in group size, Federal Fusion 140gr..... Before 2.1445"... After... 1.4355"

Difference in group size, Hornady American Gunner 140gr BTHP.... Before ...1.1950" .... After.... .7520"

Difference in group size...Creedmoor Sports 140gr Nosler BTHP... Before 1.5135"... After... .8770"

https://www.ar15.com/forums/industr...-again-UPDATED-with-Tn-G-results-/301-285762/

 

[Snuby642]

If I had any ar that held 1/2 moa I would not touch anything on it till I shot out the barrel.
For people not getting 1 moa I think the lapping is a good deal to try.

I have to re barrel a carbine that was at 7/8 - 1 moa and went south on me.
I will if I have the time do an honest test but to be fair have to break it in unlapped,
Document groups and re assemble.

Problem with that is I want to use some loktite .
Last barrel was locktited in place so I will see how big a pain it is to remove soon.

If the reciver was not lapped the bolt may need replaced due to uneaven ware?
This upper was assembled befor I had the tools by a local smith.
A couple of turns with the tool will quickly tell.

 

[Ravenous]

Here is my results with a PSA PA65... it isn't a definitive test.. but it is enough for me to start doing it to all my uppers large and small.

In a nut shell... it resulted in much smaller groups compared to before.


"Some of the rounds that showed the most improvement are ... ( no specific order.. ) Again group size does not have .264 subtracted from them.

Difference in group size, FGMM 130gr Hybrid OTM..... Before 2.3660" 5rds, .... After .9580".

Difference in group size, .Hornady 140gr ELD Match.... Before 2.2045" 5rds, .... After .9290".

Difference in group size, PRIME 130gr HPBT Match.... Before 1.9165" 5rds, .... After .9620"...

Difference in group size, Federal Fusion 140gr..... Before 2.1445"... After... 1.4355"

Difference in group size, Hornady American Gunner 140gr BTHP.... Before ...1.1950" .... After.... .7520"

Difference in group size...Creedmoor Sports 140gr Nosler BTHP... Before 1.5135"... After... .8770"

https://www.ar15.com/forums/industr...-again-UPDATED-with-Tn-G-results-/301-285762/

That's a pretty extreme shift in accuracy with your before and after. I'd be pretty pissed if I had 6.5 shooting groups around 2MOA. I'd certainly call it a success with achieving sub MOA with all the rounds after truing the receiver. Was the barrel broken in before you started the tests?

If I had any ar that held 1/2 moa I would not touch anything on it till I shot out the barrel.
For people not getting 1 moa I think the lapping is a good deal to try.

I have to re barrel a carbine that was at 7/8 - 1 moa and went south on me.
I will if I have the time do an honest test but to be fair have to break it in unlapped,
Document groups and re assemble.

Problem with that is I want to use some loktite .
Last barrel was locktited in place so I will see how big a pain it is to remove soon.

If the reciver was not lapped the bolt may need replaced due to uneaven ware?
This upper was assembled befor I had the tools by a local smith.
A couple of turns with the tool will quickly tell.

It's certainly a process to do a proper before and after but it would also be neat to see the results, if not only for your own pleasure. Just throw a torch to that receiver for a couple seconds and you should be able to remove the barrel without an issue from the Loktite.

 

[bfoosh006]

The barrel fired all the various factory ammo's first... then I TnG'd it. And fired the same boxes of ammo over again.

For that matter, I still have some of the original ammo left over.

If you read through the thread, I did TnG it around the 23 Nov. .. and did fire it at the 200 / 300 yrd ranges between the 11-23 Nov. ... if memory serves me correctly , I probably fired >50ish rounds at the 200/300

There was about slightly less then a month of time between the before and after.

The PSA fired 4 different factory rounds sub-MOA out of the box. Nosler, SiG, Federal AE 140, Horn. 120 ELD.

AND I have never claimed to be a great shot... so while some of the small before groups, might now be larger.... Lol, that is just me

I would like to point out, some results were worse.. but there was enough difference / improvements that I still lap a upper every time.

I do feel like it helps diminish fliers as well.

And as I have mentioned before IMHO ... you really have nothing to lose, and a decent amount to gain. Given the bargain aspect of the PSA upper I bought , I felt the risk was negligible. ( Again the thread discribes my thought process. )

I can't say I would be as comfortable doing it to JP / GA Precision ? insert your favorite high $ build here...

If you feel like your upper might benefit from it.... I say try it.

My results exceeded my expectations.

 

[bfoosh006]

A word about the Wheeler Tools... From My purchases...This is a perfect example of you are going to get what you pay for.

And YMMV... but ...

I bought each Wheeler size lapping tool , out of curiousity, and the overall Wheeler fit was very loose compared to my Pacific Tool and Gauge ones.

Be sure to wrap tape or something around the Wheeler shank that inserts into the upper, If you bought one.

The tape, will help center the Wheeler tool.

You really NEED the guide shank riding "true" ... if the shank tilts in the upper... you probably aren't lapping the face true / flat.

IMHO, I would wait / spend more money on a higher quality tool. I have only used the PTG tools... the snug fit requires oil / lube to turn without binding.

This is a perfect example of you are going to get what you pay for. The $10 difference is nothing compared to ammo cost.

Any savings from the poorer fitting tool, will be spend at the bench.

After all... the goal is to help not hinder.

 

[Eoddave27]

Hi @Eoddave27

What was the approximate accuracy of the guns prior to lapping and bedding?

All of them were right around 1 MOA. The lapping basically cut the group size in half. I would guess a lot depends on the barrel you are using too. If you have a battle rifle that is only capable of 1 1/2-2 MOA you probably wouldn’t see a noticeable difference. If you are trying to squeeze every last little bit of accuracy out of an AR though I think it is defiantly worth your time. Once you have the tool it is just a few extra minutes during assembly. Based on the accuracy you are already getting with your AR I would guess you had a really tight fit with your barrel and receiver. As in you needed to tap it in. If this is the case I don’t think you will see much of a benefit. Now if the receiver is out and the barrel is not a tight fit which was the case with mine the difference can be pretty substantial.

 

[Back Spin]

Thanks for the reply.

I wonder how much of the accuracy improvement was due to bedding the barrel as well?

I didn’t true the receiver face (from DSG arms), but I bedded my 16” light weight Lothar Walther blem barrel (5.56 chamber) with Loctite 271 (red). I saw approximately a 20% increase post bedding across 3 factory loads I had on hand (Sig 77 gr, Magtech 77 gr, and Gold Dot 64 gr).

Approximate 5 shot group numbers pre/post bedding:
Sig 77- pre: 1”
Post: .8”

Magtech- pre: 2”
Post: 1.6”

Gold dot- pre: 1.5”
Post: 1.2”

So there was a definite increase in accuracy with bedding alone, but not a world of difference.

 

[Primus]

Only shitty uppers need lapping. Buy a quality upper made to spec and it’s not needed. For forged BCM or billet of your choice. Most forged uppers are not machined correctly, but bcm is and they QC it.

 

[Primus]

This whole topic proves Mil-Spec is a sales pitch. No one makes a Mil-spec gun unless you are COLT or another company who is contracted, May Be FN. Spend the dough on an actual military gun from Colt. Not their AR versions $800-$1400, sporters, ect. Even now, Colt mostly cheaps out on the civilian versions as to many complained about the cost. All those QC checks cost, the extra $ for more time on a machine... A real M4, M16 ect would not need this as the dimensions would be perfect.

Correction, no one makes a commercial gun to tdp except for colt. Fun and bushmaster are prohibited from using the TDP on commercial guns. Colt isn’t because they own/owned the rights.

 

[SupressYourself]

This is a brand new Aero M5.
Note the right-hand side where the tool meets the receiver face. I put a light behind it to help illustrate.
Who knows if lapping it will make any real difference, but it will help me feel better about it.

 

[Snuby642]

Guessing 0.010 or more?

 

[Primus]

That is disgusting. With modern CNC it's actually more work to fuck it up like that than cut a 90* face

 

[SupressYourself]

Guessing 0.010 or more?

I don't know, I didn't gague it, and I haven't actually tried to lap it yet. I just got the lapping tool and was testing out the fit.

 

[Rocketvapor]

If that is the area of the index pin, so what?
How many degrees of contact do you have.
I would lap just enough to mark it. Then post a pic.

Lapping with polish, just to mark will show if that was cut straight across.
Might have been a gouge milling the slot or the threads that someone tried to cover up with a cross cut.
Don't Lap, Polish with the tool to remove anodize, photo, post here, contact your seller.

 

[SupressYourself]

It is in the index pin area. I think the way I positioned the light behind it may make it look worse than it is. However, I'm a bit hesitant to do anything with it if that hinders the possibility of returning it. Luckily, I don't really have a specific plan for this receiver at the moment, so I'm not too pressed to decide a course of action.

 

[Snuby642]

Come on you know you want to use the new tool.

Just do it.

 

[bfoosh006]

Only shitty uppers need lapping. Buy a quality upper made to spec and it’s not needed. For forged BCM or billet of your choice. Most forged uppers are not machined correctly, but bcm is and they QC it.

FWIW... even both my Rainer Arms UM billet set's showed that it "needed" it. A visual check while doing it, showed it was obvious.

I don't think it is a only low priced uppers issue.

And frankly, there is nothing to lose.

 

[Rocketvapor]

- - - so I'm not too pressed to decide a course of action.

and you are just going to let us hang here? ?

A little Metal Polish or ToothPaste will shine the anodize, maybe remove some, but will show the nature of the low spot. It could be a shipping ding, a corrective cut, and still be mostly square.
I do agree that it probably LOOKS a lot worse in the picture. To the camera it is a high contrast zone producing flare. Blowing up the image we see,

there are too few pixels to measure the gap. A macro of the area with less light might be better.

 

[SupressYourself]

Sorry, I didn't know this would be so intriguing to some, or I would have tried out some feeler gauges to see exactly what I got. I may do that when I get home.

 

[Rocketvapor]

 

[phlegethon]

"JP might.. but who takes apart their expensive JP to check ? "
Taking a JP apart might be tough since someone said they use a Hydraulic Press to push the barrel into the receiver.

JP just posted a video about their process. They make a slight large barrel extension and heat the receiver to fit them, but they are easily assembled by hand. I ended up doing the same thing when I built my AR with a Noveske billet receiver set and Larue barrel, and at ended up being my most accurate AR. Maybe it would have been even better if I’d lapped it.

The video:

 

[Almonz]

I personally do not lap my receivers. However I have never had an AR that was unusually inaccurate that made me consider doing it. I won't argue with the results, just not something I personally do.

 

[SupressYourself]

and you are just going to let us hang here? ?

I put the feeler gauges to it last night, and it's slightly less than .002 (the smallest I have).
So I think the way the picture was taken definitely makes it look worse than it is.