3-Gun Rifle Build

Here is our completed 3-Gun rifle. We are more then satisfied with the results.

3-Gun AR15 Rifle Build

Our custom built 3-Gun rifle.

If you haven’t shot a 3-Gun match, you haven’t lived.  This demanding sport requires shooters to deliver fast, accurate shots, from close to distant targets.

The rifle is perhaps the easiest of the 3-Gun firearms to customize and build for competitions.  The ideal 3-Gun rifle is quick handling, reliable, and capable of accurate fire at long distances.  Requiring just a few tools, most of which are available in the Brownells AR15/M16 Critical Tools Set, building your own 3- gun rifle can be a rewarding endeavor.  A review of the completed rifle can be found here.

Seeking the competitive edge, we carefully selected the following parts from Brownells:

Upper Receiver Parts:

Lower Receiver Parts:

This project begins by lapping the upper receiver to ensure that the barrel is square

This is our stripped YHM upper and a AR-15 lapping tool.
The lapping bar requires silicon carbide abrasive. 180 grit is recommended.
The upper is secured in a set of blocks from our Critical Tools set. The portion that contacts the inside of the upper is coated in oil. Once inserted, the 180 grit abrasive is placed on the contact surface of the lap. NOTE: It is critical that the abrasive does not enter the inside of the receiver.
We use a power drill to turn the lap and contact the face for a few seconds. We look at the face to access progress and then contact again as needed. Ideally, you want at least 80% of the surface lapped.
Here is the finished surface. The front of the receiver is now completely true.
Next, we install the forward assist.
Note the orientation of the forward assist when inserted into the upper.
Prior to inserting the forward assist, we start the forward assist retaining pin with a pin punch. The upper is supported on a bench block.
The forward assist is then inserted and the pin driven flush.
Next, we install the ejection port cover. Here are the parts: the ejection port cover assembly, hinge pin, spring and snap ring.
The snap ring is attached to the hinge pin. It simply snaps into the groove on the pin.
The hinge pin is then inserted into the upper and ejection port cover door until it reaches the cut out for the spring.
The spring is then inserted as shown. The tension holds the door open.
To install the barrel, the bolt-up plate from the RIS 2 and barrel nut are oriented as shown.
The upper is secured in vise blocks from the Critical Tools Kit. The barrel nut is torqued to 50-foot pounds using the RIS II wrench provided with the rail.
Using a roll pin punch, the gas tube is secured to the gas block with the gas tube pin.
With the gas tube inserted and pinned into the low profile gas block, the gas block is slid into position on the barrel.
Thread lock is applied to the set screws to ensure that the gas block remains secured and aligned. The White Oak Barrels are dimpled to aid in alignment.
The RIS II is slid into place and secured with the provided hex head cap screws.
Once the screws are seated, the top rail and receiver are aligned and the screws are tightened. We use a QD mount to align the rail and upper.
We selected the excellent FSC556 muzzle brake. We have found that this brake does an excellent job controlling recoil.  It includes shims to allow for proper indexing.
We selected the excellent PRI gas Buster Charging handle and WMD nickel boron coated bolt carrier group.
The oversize flat latch provides positive manipulation in match conditions, while still maintaining a small snag free profile.
A Trijicon 1-4 scope is mounted in an ADM quick detachable mount.
The ADM Recon mount has two lockable quick- detach throw levers.
The Dueck Defense rapid transition sights provide the shooter with a means to engage close range targets when the optic is magnified.  Here is the rear sight.
Here is the Dueck Defense Rapid Transition front sight. Both sights are standard A2 style.
Completed 3 Gun Upper! Note: We always check head space prior to live fire.

Building the lower receiver:

To assemble the lower, we begin with the bolt catch spring and detent. The spring is placed over the tenon of the detent and inserted into the hole.
With the spring and detent in place, we use the roll pin punch from our Critical Tools Kit to drive the bolt catch pin flush.
The magazine catch is dropped into the left side of the receiver.
The magazine release spring is placed over the threaded end from the right side. The magazine release button is threaded onto the catch.
The magazine release button can only be turned a few times before it touches the receiver. To finish installing the button, we secure a brass punch in our Multi-Vise, facing up. We align the magazine release button with the punch and press down, this drives the other end of the magazine catch out of the receiver.  We turn it to finish installing the magazine release.
Here you can see that the threaded end of the magazine release is now flush with the magazine release button. Installation of the magazine release is complete.
Installing the trigger guard in a lower requires patience. If the ears on the lower aren’t properly supported, or the pin is slightly over-sized and driven with too much force, the ear can break off and ruin your lower.
The lower is placed on a bench block and the trigger guard assembly is aligned. The trigger guard pivot pin is started with a roll pin holder.
A roll pin punch is used to drive the tigger guard pivot pin flush.
The front pivot pin spring and detent can be difficult to install. The Critical Tools kit includes the right tool to ease installation. The hole on the tool is aligned with the hole in the receiver. The spring and detent are inserted and then a small punch is used to depress the detent as the tool is slid slightly inboard. The detent and spring are now retained for front pivot pin installation.
The pivot pin is now slid into place with little effort.


For this build we selected the excellent Geiselle Super 3-Gun Trigger. The trigger includes detailed installation instructions. Notice that the trigger has two different colored trigger springs. According to the manufacture’s instructions, the gold trigger spring provides a heavier pull and is less likely to “double” then the lighter, black spring. Having seen a S3G trigger double a few times, we decided to use the heavier gold spring.
Geiselle provides a slave pin (metallic pin in trigger hole) to keep the trigger and disconnector assembly in place during installation. For a standard trigger, the parts are aligned once they are in the lower.
The trigger and disconnector assembly are dropped into place. We use a .154″ alignment tool to drive the slave pin out of the opposite side of the receiver and then guide the trigger pin into place.
The hammer and hammer spring are lowered into position. Using our alignment tool, the holes are aligned and the hammer pin is inserted.  NOTE: When the trigger and safety installations are complete, they need to be function checked to ensure safe operation.
The fire control selector is dropped into the left side of the receiver.
The fire control selector detent is placed into the bottom of the receiver.
The selector detent spring is inserted into the top of the pistol grip.
The pistol grip is slid into position and attached with the included screw.
The rear pivot pin is inserted into the right side of the receiver. Note the channel in the pin, this should be facing the rear when the pin is in place.
The buffer retainer spring and buffer retainer are placed in the hole which is forward of the threads for the receiver extension.
The receiver extension is screwed into the rear of the receiver. The buffer retainer is depressed, so the extension can clear it. Once in place, the extension holds the buffer retainer and spring in place.
The rear pivot pin detent is inserted into its hole.  The spring shown above is placed into the front of the fixed stock.
The stock is then slid into place with the detent spring placed at the front of the stock. Fixed stocks, like this MOE Rifle stock, are secured to the back of the extension with a screw.
The lower receiver is fully assembled.
Here is our completed 3-Gun rifle. We are more then satisfied with the results.


A review of the completed rifle can be found here.

For parts and ammunition for your all your 3-Gun firearms, visit Brownells.  Like everything Brownells sells, their rifle parts are backed by their 100% satisfaction guarantee

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