Beleiver in AR lapping

IMO it's the right way to do it because even if accuracy is not the main consideration, mechanical sympathy still should be. I have no idea if it will even actually make a difference in that regard, but as rule of thumb proper engagement is ideal.

Tagging to hear your results

I don't know if it made a difference with my latest build since I did it before I shot it, but it made me feel better about it.

Cheyenne Bodie said:

IMO it's the right way to do it because even if accuracy is not the main consideration, mechanical sympathy still should be. I have no idea if it will even actually make a difference in that regard, but as rule of thumb proper engagement is ideal.

Click to expand...

This. IMO it's not so much strictly about accuracy as it is about mounting the barrel truly parallel to the receiver and achieving full and consistent bolt lug engagement.

I definitely agree with the OP; once you have the tools to do it, lapping the receiver is so easy and quick, there's really no downside.

Most of you guys using the wheeler kit?

How much is a kit? I’m watching and waiting to see the results. I agree that it can’t hurt anything.

I can't speak to the wheeler kit. I'm a machinist and made my own lapping tools for small and large frame ARs. I do use the Wheeler lapping compound sometimes, but usually just use fine valve lapping compound (available from most auto parts stores).

Sogan said:

Most of you guys using the wheeler kit?

Click to expand...

I just received my three (3) G&G Rifle Works units, yesterday:
David S

http://www.gandgrifleworks.com/AR10-Lapping-Tool-ar-15-lapping-tool-p/arlap.htm

************7954


Shipping Method:

Priority 2
Order Details:

CodeItemQtyPriceGrand Total
ARLAPAR Receiver Lapping tool [AR Type:AR10]1$37.99$37.99
ARLAPAR Receiver Lapping tool [AR Type:AR15]1$37.99$37.99
ARLAPAR Receiver Lapping tool [AR Type:AERO M5E1]1$37.99$37.99

DSC-17PREZDAY
1-$17.10-$17.10

Subtotal:
$96.87

Tax:
$0.00

Shipping Cost:
$15.50

Grand Total:
$112.37

After lapping, when doing the barrel install, It's worth it to bed the barrel extension with loctite (620 I think the # was). It cut my groups almost by 1/2.

IMHO, it has worked very well for me and my AR's , Large Frame and Small Frame.

This thread show the before and after in a PSA PA65 ( 6.5CM ) , with quite a few factory loads
Please note, I also Loctite'd the barrel in place.
https://www.ar15.com/forums/industr...-again-UPDATED-with-Tn-G-results-/301-285762/

Just the best improvements....
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"




I am not a big fan of the Wheeler Tool though... it needed to be wrapped with tape for a "truer" fit into my various uppers.

I use the Pacific Tool & Gauge version... much, much better fit. As in , you better lube that shank.

Since that test, I have done it to all my uppers.

All of those barrels TnG'd ( trued and Glued ) in place , have produced excellent results.

After the purchase of the lapping tool, ( $30 ) it is just a matter of minutes to lap the upper receiver face truer.

I will continue to do it to every AR I own

riverside jeep said:

After lapping, when doing the barrel install, It's worth it to bed the barrel extension with loctite (620 I think the # was). It cut my groups almost by 1/2.

Click to expand...

How much and where do you apply the Loctite?

.001 stainless shim stock will tighten a barrel. Heat with a heatgun and install the barrel, rap it with a mallet to seat and once it cooled it will be tight as you could ask for.

Shim stock is available on eBay cheap.

timesublime said:

How much and where do you apply the Loctite?

Click to expand...

To the receiver extension , there are various different Lotite's for various different " gaps". I used Loctite 609 Sleeve retainer.

Ultimately, I believe Lapping the upper receiver face has helped minimize the dreaded flyers. And results in much more consistent groups.

My FN barrel .308 , after TnG'ing Shoots damned fine groups with about everything... who says a CHF CL Mil'Sped barrel won't be precise.... the photo is 10rds, 100yds, benched scoped bagged front and rear.. rapid fire. ( Horn. 155gr AG )



Every time I think about it... I think about the barrel extension ( when heating up ) not being able to "shift" in the upper ( no matter how little ) ... like that noise you hear when metal goes "tink" after get warm.

I realize that is an overly simplized comment... but...

Oops... here is a video that shows how easy it is... Video #3, about the 48 second mark.... ( but I suggest watching all the videos.. It is well worth it. )

https://criterionbarrels.com/media/accurizing-the-ar-15-video-series/

I've built two ARs, and used Aero upper receivers on both. Both benefited from lapping, as I could see visually that the face was not completely true. I used the Wheeler tool, and bedded both barrels with loctite. Never shot them pre-lapping, so can't do a comparison. But I do know that both barrels fit the receivers nicely and really snugged up with a good "feel". I can't say lapping is essential, but I'm pretty sure it can't hurt.

hitman said:

I see a lot of guys using Indian head gasket sealer. That is what I go to re-install this barrel since the fit is slightly loose. Do you think that is as good?

Click to expand...

I'm not sure that is quite as good as the Loctite 609.... ( and frankly, Criterion recommends the Loctite 609 in the video. )

Here is the Tech Data Sheet for the 609...
And a brief description...

• Low viscosity
• Prevents loosening and leakage from shock and vibration
• Augments press fits
• Tested to the lot requirements of Military Specification Mil-R-46082B (this is a regional approval)

LOCTITE®609is designed for the bonding of cylindrical fitting parts. The product cures when confined in the absence of air between close fitting metal surfaces and prevents loosening and leakage from shock and vibration. Typical applications include rotor to shafts infractional and subfractional horsepower motors. Locks bushings and sleeves in housings on shafts. Augments press fits.

https://tdsna.henkel.com/NA/UT/HNAUTTDS.nsf/web/3E906D6B842166B0882571870000D855/$File/609-EN.pdf

Learned something new again here. Great, I love buying reasonably priced tools that actually do a good job. My AR family will be getting some attention soon. Good Loctite recommendation as well. Thank you Hide shooters.

Looks like I’ll be purchasing some loctite and lapping tools soon

Just ordered my Loctite 609 and primer from McMaster.

Anyone use one on a seekins upper? I'd imagine it needs a smaller diameter tool since the handguard mount is built into the upper.

Lawless said:

Also, instead of loctite I used 1” wide .001 stainless shim stock to tighten my barrel. Heated with a heatgun and installed the barrel, rapped it with a mallet to seat and once it cooled it was tight as you could ask for.

Shim stock is available on eBay cheap.

Click to expand...

I do the same, also keep .0015 on hand. McMaster Carr has shim stock.

I too lap my uppers. I use the brownells tool instead of the wheeler but use wheeler compound. Loctite 609 on the barrel extension and thread anti seize on the barrel nut.

I do this to all of my ARs, can’t say if it improves things but surely can’t hurt!

My Loctite preference for this stuff is #680. It seems to have more or less the same properties as 609, but cures in a larger air gap, up to .015", so it's a bit more versatile. It's just not good for press fits, because it'll sometimes cure before you get a part pressed in place. That generally doesn't apply to this discussion though.

I posted this in another thread.
Sorry but I don't have before and after accuracy data.
I can tell you that I feel better about the fit after lapping.
That matter?
Here's what I do that NO ONE else does.
I check for squareness by lapping a little with polish. Break through the anodize.
Then lap for 360 contact.
For diameter fit I measure OD of the extension, check extension slop in the upper, then mask and spray a thin coat of High Temp paint.
Let that dry well and burnish with 800 grit paper for about a .002" increase (about 0.001" of paint).
Do a warm/cold fit up then lock in place with a barrel nut with just a heavy hand tight. Let it sit.

This is a great thread.
Good info to have.

timesublime said:

How much and where do you apply the Loctite?

Click to expand...

About 3-4 drops on the outside of the barrel extension, then smooth out so no spots are uncoated the slide into receiver, torque as required. Let cure with barrel pointed down so when in liquid state it doesn't run into chamber area , cleanup excess with rag and you are good to go. I let mine set overnight to cure before playing with it.

I lap and shim. It helps a good bit.

Testing has shown that shims are better than loctite green.

The best way to do it, if you can, take your barrel to the gun store and find which upper it doesn't fit in by hand. That's the one you want, bring it home.

Then, chuck your barrel in the freezer overnight to shrink the steel.

On the upper, use the lapping tool to get to the aluminum underneath the cerakote, anodizing etc... but not too much, you don't want to jack up the headspace. (Aero Precision has told me that all of their things are perfect and that any kind of lapping voids their warranty.... right... tell me not to do it, that's the way...) Lap just enough to show a nice complete ring of aluminum around the top and you're done. Do it vertically too, with your receiver completely vertical in your vise and use gravity to help you lap evenly. Do it by hand and check frequently. Lube the portion of the lapping tool that slides where your BCG goes. Don't you dare chuck the thing in a drill, as the instructions say, too easy to take too much off that way.

Get a heat gun (or even better your wife/gf's hair dryer) and heat the upper for good long while to expand the aluminum.
Get all your barrel nuts, shims, torque tools, M33 grease, reaction rod etc... and other stuff ready.

Pull the barrel out of the freezer, spread some Loctite 620 (sleeve retainer) on the barrel extension, work quick and shove it in the
receiver while things are still cold and hot. Grease the threads, install your nut to the proper torque (30-80 ft pounds) and then loosen it. Use a reaction rod. (Don't stress that poor barrel pin and that weak aluminum slot it goes into.) Do this three times to set the threads and on your last try do what you have to do to make sure the gas tube can get through. Let it all cure overnight and come to room temperature with the barrel vertical.

JP rifles does something similar and they order their uppers slightly out of spec so that they need to use a hydraulic press to cram it in there.

I like the shim method if needed. Question....who has shimed a upper like an Aero M5E1 for example? How difficult was it to keep the shim in place while trying to fit extension to upper.

How does lapping the face effect the headspace? It's my understanding that headspace is set with the barrel extension to barrel fit.

srt-4_uk said:

How does lapping the face effect the headspace? It's my understanding that headspace is set with the barrel extension to barrel fit.

Click to expand...

Headspace in the chamber is measured from the bolt face to wherever the extension chamber stops the bullet, somewhere along the shoulder.
When you lap the upper receiver, you're moving that point in the extension chamber closer to the bolt face.
You can also jack up the alignment of the feed ramps with too much lapping, some bullet tips might catch on the barrel extension if there is a lip there.
That's why you lap very slowly, very carefully and stop just after taking the anno/coat off.

If you can dry fit the extension to the upper you can test how janky the square is and also quick inspect to see if the feed ramps will line up and how much you can go.

No .................

pugnado said:

Headspace in the chamber is measured from the bolt face to wherever the extension chamber stops the bullet, somewhere along the shoulder.
When you lap the upper receiver, you're moving that point in the extension chamber closer to the bolt face.

Click to expand...

NO
You can check headspace without a receiver.

Hint: Some vendors will sell you a bolt 'matched' to your barrel not knowing what receiver you will be using.

pugnado said:

Headspace in the chamber is measured from the bolt face to wherever the extension chamber stops the bullet, somewhere along the shoulder.
When you lap the upper receiver, you're moving that point in the extension chamber closer to the bolt face.
You can also jack up the alignment of the feed ramps with too much lapping, some bullet tips might catch on the barrel extension if there is a lip there.
That's why you lap very slowly, very carefully and stop just after taking the anno/coat off.

If you can dry fit the extension to the upper you can test how janky the square is and also quick inspect to see if the feed ramps will line up and how much you can go.

Click to expand...

On an AR the headspace is controlled by the barrel and the bolt. Where those two are in relation to the upper doesnt matter (within reason). If you dont use reasoning then yeah, take some tenths off the upper and you could have issues. That would be an epic shit ton of lapping though.

As rocket vapor said, to check headspace on an ar you dont even need the upper.

BUT, you do need a barrel.
Just an extension and a bolt won't do it

That's what I thought. I just wanted to make sure.

Rocketvapor said:

No .................


NO
You can check headspace without a receiver.

Hint: Some vendors will sell you a bolt 'matched' to your barrel not knowing what receiver you will be using.

Click to expand...

The way vendors do it is they grab a random bolt from a pile, a random barrel, shove a go/no-go gauge in there, then by hand, twist the bolt in and call it good if it locks on the go and doesn't on the no-go. Is that how your bolt works inside a bolt carrier?

The next time you do an AR, but before you put the barrel on, install the bolt in a carrier and send it home, letting the cam pin and upper twist the bolt and make note of where the bolt face stops and can't go any further. Smash the forward assist a few times if you want. Measure from there to the end of the upper receiver threads. Now imagine the shoulder inside of the cup of the chamber getting closer to that bolt face if you were to grind down those threads. Will the bolt move back a bit if it's too short for the brass you put in it? Sure, there's usually enough play before it'll start grinding too hard on the extension lugs, but it's hard on the bolt and the base of the brass.

Edit: another reason why you might want to square things up, having extension lugs not parallel and aligned to the bolt lugs wears both the bolt and the chamber down.

OK then.
You got it dude.
So sorry I disagreed with you.

Told you guys, NO ONE does it like I do.

Think about what you are doing. Put a no go gauge in the gun. Bolt will not close because the lugs cannot go all the way in the extension and engage. If you move the carrier closer, the bolt still cannot close because the distance the bolt can go into the extension did not change.

Rocketvapor said:

OK then.
You got it dude.
So sorry I disagreed with you.

Told you guys, NO ONE does it like I do.

Click to expand...

You have it correct. A proper headspace is with the barrel and barrel extension in the upper receiver. Otherwise, the dimensions change once installed.

Just being polite.
Let me tell you, I'm a Know-It-All.
I KNOW I got it right

Ripdog, check the second sentence of your post.

srt-4_uk said:

Think about what you are doing. Put a no go gauge in the gun. Bolt will not close because the lugs cannot go all the way in the extension and engage. If you move the carrier further away, the bolt still cannot close because the distance the bolt can go into the extension did not change.

Click to expand...

Someone try this on their next build, before the barrel is torqued on:

1. Assemble the BCG with bolt, cam pin etc... and put it in the upper as you normally would.
2. Without installing the barrel to the upper, put a no-go gauge in the barrel.
3. Dry fit the barrel to the receiver, push it in all the way as far as it can go but don't install the nut.
4. Drop the bolt home gently and finish up with some forward assist. Does it lock on the no go gauge?
5. Where is the barrel now? Did it move forward past the end of where the ring/pin would contact the threads?

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.

You mean like this?


What is stopping the BCG? Why doesn't the bolt rotate into position?

Nice lapping job, right?

how do you increase the distance between the barrel extension and the barrel face by moving the two of them equal amounts forward?

Ripdog28 said:

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.

Click to expand...

There's nothing special about Mil-spec. They're just dimensions with tolerances and as long as accumulated tolerances don't cause a malfunction it's good to go. Military is all about when the trigger is pulled a bullet comes out each and every time without fail, accuracy is secondary.

Lapping the upper and shimming etc... is done for optimizing accuracy, and yeah like others have mentioned if you do it wrong you could introduce failure. That's why military uppers aren't messed with.

Head spacing is only needed on the AR15 market because they are not made to (Mil Spec) TDP (Technical Data Package). Many modern AR manufacturers use 6061, which is also not the specified 7075 according to TDP. Heck if you see a barrel called mil spec 4150, that is wrong as the TDP also calls for MIL-B-11595E which has a higher content of Vanadium than 4150. If a company has the TDP, head spacing is already build into the manufacturing process. The Barrel/Barrel Nut and Receiver are all in spec.

pugnado said:

There's nothing special about Mil-spec. They're just dimensions with tolerances and as long as accumulated tolerances don't cause a malfunction it's good to go. Military is all about when the trigger is pulled a bullet comes out each and every time without fail, accuracy is secondary.

Lapping the upper and shimming etc... is done for optimizing accuracy, and yeah like others have mentioned if you do it wrong you could introduce failure. That's why military uppers aren't messed with.

Click to expand...

I would disagree with you based on the lengthy time I have spent in class with people who manufacturer these guns according to TDP. The dimensions are perfect if build to TDP, no lapping needed/truing of faces is needed.