I saw recently, when looking at X-caliber barrels, that they have a lapping tool for truing AR receivers.

They show still pictures of the lapping process and how on a receiver the anodizing will wear on one side as the lapping progresses.

The lapping tool is about $100.00.

Have any of you guys gone to this length when building an AR? (Ron? anyone?)

Gluing?



What? How?

I prefer to let the BCG do the lapping work for me. During live fire, of course.

Seems unnecessary to me. Plenty accurate AR's exist without this service.

Compliments of Old N' Cranky:

http://bulletin.accurateshooter.com/201 ... -revealed/

I true all of mine

Some uppers are pretty good, others not so much. You can see how off it is as the anodizing gets worn through. Brand doesn't seem to matter. I've had Anderson uppers that barely needed anything and BCM uppers that took a while to get all the way around. Forge marks are the same. Cerro, Anchor Harvey, etc. I haven't noticed a difference, but I've only done a dozen or so.

I can't say that accuracy will improve greatly just by lapping the upper. Reliability and longevity certainly will. The bolt has a bit of freedom inside the carrier. Once it's locked up with the barrel extension it should be fairly square to the chamber (unless the receiver face is terribly off). Even with the face off a bit it will run. Proper alignment just ensures that the bolt hits the barrel squarely every time. One side of the bolt isn't going to hit first and stress that side over and over again.

When I build an upper I'm not satisfied until the bolt slides into the barrel extension with very little effort (gas tube alignment plays a role in this too). The test is to hold the upper (by itself) upside down and release the BCG from the rearmost point of travel. With no other pressure it should slide into the barrel extension and lock up. The angle I can hold it at to make that happen tells me how good of a job I did. The more shallow the better.

Another benefit of lapping is that the barrel will center inside a free float hand guard. That's important for a few reasons. If you run a suppressor under the hand guard with limited clearance it keeps things from touching. It also affects windage on your rear sight. If your front sight is on the float tube and the barrel is pointing somewhere else you're going to have to crank the sights and optics to one side to make it work.

I'm just going to FUD out and say I'm not glueing any barrels to any receivers. I get less than 3/4" groups at 200yds with a good does of anti-seize around the barrel extension.

I believe that’s what he’s talking about.


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Some good bits in there. Thanks.

I’m not getting your point

You’re saying that you don’t glue them together, but you do?


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^^^ I'm confused too.

So... is anti seize the same as "gluing" in the linked article?

No. Dana said he was going to use anti seize. The article says to use GLUE. They have opposite functions, I believe.

Marine-tex rapid set is the glue to which I was directed.

What/who's lapping tool do you use, RS?

No. I am not glueing any receivers and barrels together.

That article said to do so.

I'm still not going to do it.

Based on my myopic opinion of using automotive Anti-Seize on the barrel extension and still getting less than 3/4" groups at 200yds. I ain't glueing or using any thread locker to any barrels and receivers.

We true receivers for any builds we do in shop. Especially if it’s a Cerakoted build to ensure the coating is even.

Some customers do request we skip the step, but for the most part everyone is happy with the process. Especially when they watch us during assembly and don’t realize it’s included for no charge.

We do not glue barrels in. It’s not necessary, especially if the install is after coating.