If you’re like us, you not only enjoy shooting your guns, you also take pride in cleaning and modifying them as well. A little bit of customization turns a great firearm into an even better one by tailoring it to suit the shooter’s methods and style and even increasing its performance potential.

In our new section, Specialized, we take a look at the dedicated armorer’s tools that you won’t find at your local hardware store. Armorer’s tools can be used to improve, repair or maintain firearms with ease. We figure out what these (sometimes obscure) tools are used for, put them through their paces, demonstrate how to use them and tell you what we think about them. In this installment, we focus on two AR-15 upper receiver–specific tools.


Brownells AR-15/M16 Upper Receiver Lapping Tool

What Does It Do?

Brownells claims that this lapping tool “helps true upper receivers for precise barrel fit and maximum accuracy.” In other words, it helps ensure a precise fit between the barrel extension and the receiver’s surface for added shot accuracy.

Because metal coatings can create an uneven surface where the receiver meets the lip of the barrel extension, it’s possible the barrel may not sit completely flat against the upper receiver, causing the barrel not to “point straight.”

The lapping tool attaches to a 3/8-inch hand drill to easily “square” the upper receiver face on your AR-15. By using a lapping compound, the tool sands down excess metal coating and allows for a more precise mating of the barrel and upper receiver.

How To Use It

  1. Strip the upper receiver of the barrel, clean, inspect and remove any burrs or debris if found. (Not Pictured)
  2. Mount upper receiver onto an action block and vise. (The vise should be bolted onto a sturdy surface. The image shown is for demonstrative purposes only.)
  3. Clean lapping tool and lubricate its pilot sections. Here, we use a lubricant called FIREClean.
  4. Apply lapping compound to the face of the lapping section of the tool. Be careful not to allow lapping compound to get onto the pilot section. You want to smooth down the receiver’s face without scratching its interior.
  5. With the upper receiver held securely in an action block, insert Brownells AR-15/M16 Upper Receiver Lapping Tool into the front of the receiver. Make sure the tool rotates freely in the upper.
  6. Attach an electric hand drill to the tool’s 3⁄8-inch shank. Apply firm forward pressure and use a moderately high drill speed. After 10 to 15 seconds of lapping, remove the tool and inspect the receiver face. You should see that a portion of the face has been shaved and the anodizing has been removed.
  7. Clean the tool and the upper, and repeat the lapping procedure until a minimum of 80 percent of the receiver face has been trued. Reassemble the firearm according to the manufacturer’s instructions. Check for proper and safe functioning before firing with live ammunition.

Does It Work?

From what we observed, yes it does. If you think about it, it’s a simple solution to a problem many of us never realized we had. We had an upper where the gas block was clearly sitting a fraction of an inch closer to one side of the interior of the rail than the other. After using the Brownells AR-15/M16 Upper Receiver Lapping Tool on this upper, the gas block sat perfectly dead center. After seeing that firsthand, we now use it to square all of our uppers.

  • Make: Brownells
  • Model: AR-15/M16 Upper Receiver Lapping Tool
  • MSRP: $34.95

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