January 03, 2011
Building an accurate AR varminter in .204 Ruger from a pile of parts is so easy, even the author could do it.
Despite the best efforts of our enemies and the insane rants of the clueless on both sides of the Second Amendment fence, the AR-15 truly is America's rifle. Doubt me? Take a quick stroll through the aisles of your local gun show (provided you don't live in, say, California), or peruse the latest Shotgun News, and you'll see that AR-style rifles and parts make up a solid percentage of the available wares. And when it comes to accessories, no rifle I know of has as wide a variety of parts and doodads just begging to be bolted, strapped, or clamped on as the good ol' AR.
The right tools make everything easy. This barrel fixture makes it easy to hold a barrel securely without damaging it.
Besides the obvious benefit of being the semiautomatic twin of our country's service rifle, the AR is so popular because it is so darn versatile. Different barrel lengths and contours, countless sight and scope configurations, and a wide variety of calibers mean there is almost certainly some AR flavor to suit your fancy.
I am a good shooter and a reasonable handloader, but I am not the most tool-savvy guy in the world. Still, it seems that I am constantly stumbling my way through assembling and disassembling various AR-15s as I add or replace parts in my quest to bolt as much as I possibly can onto my black guns.
Recently, as I helped a friend replace the trigger on his AR-15, I came to the realization that for once I actually knew what I was doing. That realization and my recent infatuation with the fun little .204 Ruger cartridge inspired me to order the parts necessary to build my own rifle.
good bench block makes driving the AR's many roll pins easy.
I became interested in the .204 Ruger because of its low recoil and its excellence as a prairie-poodle death ray.
Consequently, I decided to build a heavy-barreled precision rifle to take advantage of the flat-shooting cartridge. Based on an excellent reputation as a manufacturer of quality rifles and parts, including .204 Ruger rifles and uppers, I ordered my components from DPMS.
Parts & Tools
Coming up with the parts was fairly simple. I called up DPMS and ordered a stripped lower, a Lower Receiver Parts Kit, a fixed A-2 buttstock, and all the necessary parts to mount it. I also ordered a flattop upper; a round, aluminum handguard; a 24-inch fluted barrel in .204 Ruger; a Picatinny gas block; and a rifle-length gas tube.
Next, I called Timney Manufacturing Inc. and ordered a modular AR trigger. I have installed this trigger before on other carbines and found it to be reliable, safe, and easy to install. The Timney modular trigger gives a light, crisp, single-stage pull that I really like. These units have been so popular that they are constantly on back-order. Fortunately, a new batch had just arrived, so I got my hands on one immediately.
Before assembling the upper or lower, lay out all the parts and make sure they are all present.
Once I had all the parts gathered up, I called Larry Weeks of Brownells to discuss my project. He asked a few questions and helped me put together the perfect tools for the job. They showed up on my doorstep two days later.
This photo shows the lower with the stock attached and magazine catch assembled. It is still shy a few parts, including the trigger, which is clearly visible here.
I will not go in to a step-by-step description of how I assembled the rifle. Rather, I would like to cover a few key parts of the assembly process. If you require complete instructions, both
My new tools included an AR-15 receiver action block, a roll-pin punch set, and an AR-15 armorer's wrench. A vise, mallet, No. 10 screwdriver, antiseize lubricant, and some duct tape rounded out my armorer's kit.
MidwayUSA and Brownells offer several good books and videos on the subject. Internet sites like AR15.com also have good information on building your own AR.
The Lower Receiver
I built the gun under the watchful eye of my good friend Wes Webber. Wes is a firearms instructor and armorer at a suburban sheriff's department, and he's very knowledgeable when it comes to ARs. Fortunately, he is also quite patient.
A good action block enables you to get a good grip on the receiver without marring or crushing it.
I started out by laying out all the parts for the lower on the workbench. Next, I compared my parts to the diagram and parts list DPMS provided with the kit. When I verified that all the parts were present, I started putting it together.
First, I taped the raised portion on the left side of the receiver, which contains the offside of the magazine catch to keep from scratching it before inserting the magazine catch from the left side of the receiver. Then, I put the magazine-catch spring on the catch and screwed the magazine release onto the threaded portion of the magazine catch. After giving it a few turns, I pushed it in with my punch and turned the magazine catch clockwise. I stopped when the post fit flush in the magazine release.
The bolt catch was the next bugaboo. Installing it was pretty straightforward, but the challenge was doing it without marring the receiver. I know two tricks to make it painless. Unfortunately, I didn't think to use either.
The indexing detent on the upper receiver is shown here, and the corresponding pin on the barrel is also clearly visible.
One way to install the bolt catch without marring the finish is to tape the receiver just behind the catch and tap in the pin with a roll-pin punch. That's how I did it, but I forgot the tape. Consequently, I have a few little marks on my receiver that I wish weren't there.
Once the barrel is in place, the handguard is threaded onto the upper receiver to approximately 30 ft-lbs. The gas tube hole in the handguard must match up with the one in the receiver, so make sure they are properly aligned.
To avoid this, use an old trick a buddy taught me--press the pin in with pliers. To do it, wrap the jaws of a set of Vise Grip pliers with tape and adjust them so they barely hold the pin lengthwise with the handles together. Then hold the roll pin in place on the receiver with needle-nose pliers (a little lubricant helps a lot here), open the Vice Grips, and place one jaw on the end of the pin and the other on the protrusion on the receiver. Twist the handle of the Vise Grips a turn or two at a time so the pin slides through the holes in both the receiver and the bolt catch. With the pin almost seated, a few gentle taps with a mallet--don't forget to tape the receiver--will drive it all the way home and leave the finish unmarred. Many of the AR's pins can be pressed in this fashion, resulting in a gun that looks new, as opposed to the rode-hard, put-up-wet look that's all too common among hobbyist-built rifles.
Without the right tool, the pivot-pin assembly is, in my opinion, the hardest part to install on the whole rifle. I have a tool, but I left it on the counter when I drove an hour to Webber's house to assemble the rifle. So I had to monkey with it for half an hour to get the pin in place.
With the installation tool, it's simply a matter of inserting the tool, sliding the spring and detent into the receiver, compressing the detent pin with a punch, and rotating the tool. Once everything is in place, insert the pivot pin from the other side and slowly rotate it until the detent is in the groove and push it in to push out the tool. Without the tool, it's a matter of luck, manual dexterity, and lots of bad words. Buy the tool.
With the hard bits out of the way, I installed the trigger. This can take a bit of effort, but playing with the parts ahead of time to see how they fit together is a big help. Installing a Timney trigger is the easiest fix.
The handguard is tightened with the aid of an armorer's tool and a torque wrench.
I simply dropped in the Timney, installed the safety selector and the trigger pins, and then I tightened the two hex-head screws in the trigger assembly. The entire process took less than five minutes.
From there, all I had to do was install the trigger guard, buffer tube, buffer spring, buffer, stock, pistol grip, and various pins, springs and detents before moving on to the upper receiver.
The Upper Receiver
I must confess that DPMS made a mistake on my upper. I ordered parts but received a complete upper instead. I would have thought of it as a gift had the subject of this piece not been assembling my own AR. So, I disassembled the whole damned thing and laid out all the parts so I could put them back together.
My Brownells action block was a big help in assembling the upper. After tightening it down in the vice, I applied some antiseize lubricant to the barrel extension and tapped the barrel in to the index point.
Before heading to the shooting range to test-fire the AR the author built, he put the finished rifle through a thorough inspection and installed a Leupold 3.5-10X LR/T scope.
Next, I applied lubricant to the receiver threads and tightened the handguard. The manual says to torque the handguard to 30 ft-lbs, but you may have to tighten it a little more or less to align the gas-tube holes.
Once the barrel and handguard were installed, the gas block was a cinch. First, I slid the gas tube in and out a few times to make sure it was not binding in the gas-tube holes in the receiver or the handguard. When I saw that was problem-free, I installed the gas block and tightened the setscrews securely. After function-testing everything, I tightened the gas block's set screws with Loctite.
With its black finish and stainless, 24-inch bull barrel, the finished rifle is a good-looking piece. Fit and finish were excellent (save for a few builder-added "beauty marks"), and the Timney trigger provided a crisp, clean trigger that broke religiously at a hair under 3 pounds. I was anxious to shoot it, but I had to do a basic inspection before I could safely fire my new rifle.
The author fired this 1.46-inch group at 200 yards; it's darn good given the unbearable heat and gusting wind.
I started out by checking to make sure everything was tight and that the controls functioned as they should. I tested the safety, the trigger pull, and the forward assist. I also checked to make sure the charging handle didn't bind and that the bolt worked smoothly.
The bolt and bolt carrier also required a close examination. I checked the carrier to make sure it was nice and tight, and that its screws were securely staked. I checked the extractor hook for damage and correct tension by inserting a cartridge case in the boltface (with the bolt out of the gun, of course), and then I checked for firing-pin protrusion. I also checked the headspace with go/no-go gauges.
You should always check the headspace before shooting a rifle you have assembled. However, for this project, since the upper originally came assembled, I knew the headspace had already been checked at the factory, so I did not perform this step.
When everything checked out, I cleaned and lubricated the rifle in p
reparation for test-firing.
On The Range
For my shooting test, I mounted a Leupold 3.5-10X LR/T scope in a set of Leupold Mark 4 rings on the AR. Although I ordered ammunition from Hornady, Winchester, and Federal, only the Federal ammunition arrived in time to meet my deadline for this story, so I packed up what I had and headed off to the South Texas ranch of Irvin Barnhart to see the results of my handiwork.
This five-shot group was fired at 100 yards. It measured an impressive 0.564 inch, but the author believes the rifle will shoot even better once it is properly broken-in.
I fired the first few rounds by single-loading from the magazine to verify that everything was assembled correctly and that the bolt catch worked properly. It did, so I fired another dozen rounds that I loaded two at a time to verify feeding. Things were moving along nicely, so I loaded a 20-round magazine and fired it as fast as I could squeeze the trigger. The new rifle performed perfectly.
Once the rifle passed my function tests, I zeroed it at 100 yards and got it hitting where I wanted it to hit. I then fired 10 five-shot groups with the aid of a solid benchrest, a Harris bipod, and a rear sandbag.
My first group measured a disappointing 2 inches, but I suspected that poor performance was my own doing. My persistence paid off as subsequent groups got better and better. My best 100-yard group measured 0.564 inch. From the 200-yard line, I shot several five-shot groups under 2 inches despite searing heat and gusting wind; two of the groups measured 1.46 inches and 1.58 inches, respectively.
The author test-firing the new rifle in South Texas. Note the ejected brass near his right hand.
Time was running short, and I didn't have any other ammunition, but the Federal load, which pushes a 32-grain Nosler Ballistic Tip at a claimed 4030 fps, definitely showed promise. A different load may shoot even better, but I'm quite certain a clean, properly broken-in barrel will yield a significant improvement.
Just Do It Yourself
A few years ago, changing grips was about the extent of my gunsmithing ability. But with a little patience and a willingness to learn, I have performed countless AR modifications over the last 2 years. Heck, I've even built an entire gun successfully.
The cartridge indicates some minor marring. The author should have taped these areas before tapping in the pins. Or better yet, he could have pressed in the pins.
If a do-it-yourself project appeals to you, just do it. It's a lot easier and more fun than you might think. And nothing can match the sense of pride you'll feel from zapping prairie poodles way out yonder with a gun you built yourself.