Best AR-15 Tools to Build the Ultimate DIY Rifle – Firearms News


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Unlike many of my contemporaries, I have been building, repairing and customizing AR-15 type rifles for several decades. I think I have a pretty good feel for what tools are needed and those that are mainly luxuries. Some tools fit more into the realm of the professional builder, and some are mainly geared toward home hobbyists. I will try to point out the differences. Many tools/fixtures designed for AR-15s are simply holding devices designed to hold the upper or lower receivers rigidly in a vise while the build commences (yes, you need a good vise). So, we’ll start with those.

Complete Tool Kits

Real Avid’s AR15 Master Armorer’s Kit displaying its contents.

Many of the tools in this article are mostly used by professional gunsmiths, but let’s say you’re a home hobbyist interested in building ARs for your personal use. You currently have no tools to accomplish that task. Maybe you need a basic tool kit to get you started. Also, you have limited space. There is one bench available, but you’re sharing it with your spouse. It’s your gunsmithing, auto repair and general maintenance bench but also her crafting bench. What to do? Real Avid has a solution in their AR15 Armorer’s Master Kit. In one convenient carrying case, they packed all the basic tools necessary for AR assembly, including punches, torque wrench, barreling spud, Armorer’s Master Wrench combination tool, Smart Fit lower receiver block, bench block and more. You will still need a vise, but they make a unique vise for working on guns, too. When you’re done with your project, simply stuff the tools back in the case and slide it under the bench. Also included in the kit is a booklet entitled Top 18 Mods Every AR Owner Should Master with helpful hints and projects for your new tool set.

Lower Receiver Holding Devices

The Real Avid Smart Fit block (Left) that adjusts for tightness in 5.56mm magazine wells which can be slightly different in size. Midwest Industries vise block/bench blocks (Right) for 5.56mm and .308 receivers. It can be used as a bench block or to pin a gas tube.

Forty or even thirty years ago, there were few AR-15 tools available commercially. You could get a G.I.-type-barrel wrench back then, which also had features to remove flash hiders (three-prong and birdcage), but most specialized tools had to be fabricated. Luckily, I had a good local machine shop that would make anything I wanted. How would I hold a lower receiver in the vise? I had an aluminum block in the shape of a 20-round magazine fabricated, and I have used it since the 1980s. Clamp it in the vise, drop the lower on to it and done. Yes, the block had to be made a bit smaller than the mag well so it would fit all of them, and the lower wobbled slightly with this setup, but it has served faithfully for many years. Now, of course, there are many variations of the vise block available commercially. We will touch on a few below. From Real Avid, we have an interesting variation on my old vise block that adjusts for tightness (!) to fit any 5.56mm size magazine well. This tool caught my eye before I was assigned this article, so I have been using it for a while. It works. Constructed mainly from plastic and aluminum, the Real Avid Smart Fit block is inserted into the mag well, and the handle on the bottom is tightened to expand the block for a tight fit. This design seems so logical I can’t believe someone didn’t manufacture one sooner. The lower receiver can be held securely either right side up or inverted allowing a vise to be your third hand when installing triggers, buffer tubes, pivot pins, etc. I think the Smart Fit block has really raised the bar for mag well blocks in general, and it’s a must have item if you are a hobbyist or armorer assembling rifles.


From Midwest Industries comes their take on a lower receiver block with a twist. It’s a combo mag well vise block and bench block. Molded from a dense blue polymer, it provides screw holes for mounting to your bench if you wish. As a bench block, it is claimed to fit any mil-spec lower receiver (I understand semi-auto receivers aren’t really mil-spec, but you know what I mean). Your typical forged standard lower receiver from any number of makers will sit level on the block with the right side down without the pistol grip installed. The block could be easily modified for clearance of the pistol grip, and I don’t see why it isn’t manufactured that way. Due to variations in the outside dimensions of billet receivers, they may or may not fit. With the receiver sitting flat in the bench block, the right ear of the trigger guard should be supported for driving in the roll pin. These ears are relatively fragile, so good support is important to avoid breaking one off. The trigger and hammer pins can also be pushed out in this position. On the flip side of the block is a spot designed to support low-profile gas blocks while pinning the gas tube. This is the best feature of the block in my opinion. A typical Mk12 style gas block fits quite well. Of course, the installer will still have to be careful not to let the gas tube rotate as the pin is driven into the block.

I test fitted the mag well vise block in six different receivers from Salient Arms, Aero (M4E1), Aero standard, Rock River, Mega Arms and Spike’s Tactical. All these lowers fit the block although the mag catch on the Rock River and Spike’s receivers did not lock into the groove. Shaving the top of the groove in the block very slightly would remedy that situation but I don’t think it’s important. The sides of the block are machined parallel for a secure fit in a vise and the contact area is five-inches long, so it was very solid in my eight-inch-jawed vise.

Buffer Tube Holding Device

Geiselle Reaction Block buffer tube holding fixture.

How do you hold the lower receiver assembly at the buffer tube to tighten/torque a castle nut, stake the nut to the end plate, install a pistol grip and hold the lower in different positions while assembling it? Geissele Automatics has a solution they refer to as the “Reaction Block.” When mounted in a vise, the Reaction Block will capture the buffer tube in four positions at 3, 6, 9 and 12 o’clock and hold it rigidly. I mainly use it to torque castle nuts. Slide the buffer tube into the block in the desired position and tighten the three nylon screws finger tight. It’s that simple. 


Gas Block Tools

A front sight in position for pin removal with a Brownell’s Front Sight Bench Block (Top Right) and drive punch. A collection of barrel dimpling tools from SLR Rifleworks, KAK Industries and Black Rifle Disease Engineering (bottom right). Dimpling a barrel with an SLR Rifleworks dimpling tool (Left).

And, speaking of bench blocks, a block I have used for many years to remove/install taper pins in AR-15 front sight assemblies is the Brownell’s Front Sight Bench Block. Although pinned front sights are not as common as they used to be, there are many still out there, and removing the taper pins can be a chore. Supporting the front sight on a solid block inletted to fit it makes the job easier. The block is clearly marked “IN” and “OUT” on the appropriate sides, so you don’t try to drive the pins from the wrong end. My personal block in the photo shows a lot of hard use, but I have found it invaluable. Make sure you pair the block with a Starrett taper pin starter punch. Factory taper pins have rounded ends, and its concave tip is designed to start them moving without slipping off the pin and scarring the front sight housing. Nothing screams “amateur” like scratches around taper pin holes. I have worn out several of these punches over the years. Consider them expendable and buy a couple.

Have you ever wished you could pin a gas block? A couple set screws holding your run of the mill gas block are ok for range play, but pinning the block makes it bomb proof for tactical use. For more than a dozen years I have used a block from Black Rifle Disease Engineering designed to pin a standard Vltor or BCM gas block in a drill press. Position the gas block on the barrel with set screws. Slide the fixture over the gas block and run a drill through the hole (or drill bushing on newer blocks). Done. Now drive a straight dowel pin through the drilled hole and the gas block will never move. You could also use a taper pin reamer to install a taper pin instead of the straight pin if you wish. All Black Rifle Disease products are made in the USA in Minnesota. They also make an excellent barrel dimpling tool.

It always ticks me off when I buy a premium quality barrel and it is not dimpled on the bottom side opposite the gas port to position the gas block. How tough is it to add an extra line of code to the program on a CNC machine to spot drill a barrel? Sometimes, you must do it yourself. Most dimpling tools consist of a collar which fits over the gas block journal on the barrel with a pointed screw that is inserted into the gas port on the top and a drill bushing or drill sized hole directly opposite it on the bottom. The barrel is held in a drill vise upside down and a drill is used to spot a shallow dimple for the rear screw of the gas block. When the gas block is installed, this dimple will align the block perfectly with the gas port. The holes in gas blocks are usually much larger than the gas port itself, so alignment isn’t tough. Different diameter barrels will require different collars, with .750 inch being the most common. You can dimple the barrel for both screws on the gas block, but keep in mind that the distances between screws may vary. I don’t think spotting both screws is necessary, but it doesn’t hurt. Always use set screws with serrated tips when possible. The serrations bite into the steel for better holding power. Don’t forget the Loctite. Dimpling tools are available from Black Rifle Disease Engineering. Many barrels today are nitride, so the finish is hard but thin. Grind off a spot where your dimple will be or a standard HSS drill may not cut. A dimpling jig is a small investment with big rewards.

Gas Tube Wrench

Ever try to remove a gas tube that is stuck in a front sight/gas block without destroying it? This has happened to me many times. What do you use to grab the tube? I use a Mark Brown Gas Tube Wrench from Brownells. You don’t need it all the time, but when you need it, you REALLY NEED it if you get my drift. I didn’t initially consider adding it to this article until I was using it a few minutes ago to remove a tube from a 30-year-old rifle. Indispensable!

Upper Receiver Holding Devices

(Top Left) Barreling spuds left to right: Real Avid, Geiselle, 2 Unique, Brownell’s, Geiselle (.308) and Knight’s Armament. The Device Manufacturing upper receiver holding fixtures (right). A Device holds an upper receiver in a vise for port door installation.

Over the years, there have been numerous attempts to create an upper receiver vise block of some kind, and I have a few kicking around the shop, but none were successful in my opinion. Usually, they consisted of a block of nylon or aluminum with slots cut to fit the receiver lugs and cross pins to lock it in place. None of them were durable enough to be considered professional grade. Enter “The Device” by The Device Manufacturing, LLC. This product consists of a beefy block of 7075 aluminum with square cuts to accept the receiver lugs and a t-handle wedge that inserts through the rear of the receiver to hold it tightly against the block. The upper receiver is held solidly and level in a vise. In this position, forward assists and ejection port doors may be installed or removed, optics may be mounted and leveled, A2 rear sights can be worked, and rail systems may be installed. Flip The Device over and you are looking at a 1913 Picatinny rail. In this position, an optic may be mounted and leveled in rings or a one-piece mount, or an optic may be repaired. I have been using the Mk1Mod0 version of The Device for a while, and I like it. The biggest drawback from the point of view of the home hobbyist is price ($299.99 from Brownell’s. Unless you’re a licensed manufacturer or professional armorer, that cost may be a bridge too far. Recently, a new Mk3 Device “Lite” was introduced at a lower cost. Made from 6061 aluminum with no pic rail on the bottom, this version is more suited to everyman. At $199.99, it’s still not cheap, and it retains most of the functions of its predecessor for a lower cost.

Barreling Spuds

An upper receiver held on its side by a Real Avid Lug Lok barreling spud.

The most useful AR-15 tool introduced into the retail market in at least the last decade is the barreling spud. Commercial assemblers had been using a similar device for years, but they weren’t available to the hobbyist or gunsmith until Geissele released the “Reaction Rod.” Essentially, a one-inch piece of round steel stock with flats machined on one end to fit in a vise, the working end has splines which fit into the AR-15 barrel extension, providing solid steel on steel resistance when torquing or removing a barrel nut. Prior to this, there were hokey plastic blocks designed to support the upper receiver when installing a barrel. When a tight barrel nut was being removed, the blocks would twist in the vice, and a percentage of the torque would be lost to poor tool design. I have removed factory barrel nuts more than once that required close to 100 foot-pounds to break loose. The Geissele product has been around for a while, and many clones have appeared. Let’s look at a couple of new and improved barreling spuds.

From Real Avid comes the Lug-Lok upper vise block. This tool is machined from a bar of aluminum with a flat end to fit in the vise and a splined end for the receiver extension like most barreling spuds. Unlike the others, this spud has holes drilled through the tail for pins that fit above and below the vise jaws to stabilize the tool in the vise preventing it from drooping downward toward the bench when an upper receiver assembly is installed. I modified my Geissele Reaction Rod with two pieces of flat bar years ago to keep it stable at a slight upward angle so the receiver wouldn’t slide off. Kudos to Real Avid for correcting this problem with barreling spuds. Holes drilled in the circumference of the Lug Lok accept a block which is inserted through the open bottom of the receiver to keep it from rotating and for positioning it at multiple angles for various tasks. I haven’t used this product extensively yet, but for $80 it looks like a good value.

There is also a slightly more expensive version for .308 ARs. From 2 Unique, LLC in Maine comes their “M16 Barreling Spud.” Beautifully machined from 4140 steel and black nitride treated, this tool incorporates a block that fits into the charging handle channel to prevent receiver rotation. Not cheap at $175, but professional grade tools never are. The owner of the 2 Unique machine shop used to work for Bushmaster assembling rifles, so he has a good idea what makes sense in the realm of AR tooling. Midwest Industries Upper Receiver Rod is similar to the 2 Unique product and is also machined from 4140 steel with an anti-rotation block installed for $109.95 from Brownell’s. A .308 version is also available.

Geissele Automatics has introduced an improved version of their original Reaction Rod, the Super Reaction Rod which incorporates an optional system to keep the upper receiver from rotating. The anti-rotation locks can be removed so the tool functions like the basic Reaction Rod. Barreling spuds are a must-have for AR-15/M-16 armorers. I think for a professional armorer or gunsmith who barrels ARs a lot, I would go with a steel spud. But for the average hobbyist who barrels guns occasionally, the aluminum product is fine. Spuds will not work on blowback operated pistol caliber or .22LR ARs that lack conventional barrel extensions.

Barrel Nut Wrenches

The Master Fit A2 Crowfoot Wrench (Top) set from Real Avid includes a 10 to 150 ft-lb torque wrench. The Real Avid Armorer’s Master Wrench serves as a barrel nut wrench, castle nut wrench and hammer.

Years ago, if an armorer had a G.I. barrel nut wrench, a breaker bar and a torque wrench, he was good to go. There was only one type of nut to contend with. With the rise of free-float handguards and rail systems, everything changed. Some nuts became proprietary to different manufacturers, so armorers had to adapt. The breaker bar and torque wrench were still needed, but wrench heads appeared in a wide variety of patterns. You can literally fill a toolbox with accumulated wrench heads if you do commercial work on AR-15s. I think manufacturers should provide a wrench head with their product if it employs a proprietary nut like Aero Precision does, but some sell them separately, so you have to add the cost of the wrench to the total cost of the job.

Most full-length nut wrenches are designed to fit G.I. type barrel nuts and include a 3/4-inch notch for tightening muzzle devices and a 1/2-inch square drive hole for a torque wrench. Magpul, Smith Enterprise, Real Avid, Brownell’s, Midwest Industries and 2 Unique all produce full-length wrenches along with other companies. Barrel nuts may vary slightly, so having more than one wrench on hand is not a bad thing. Select a wrench that fits a particular nut without a lot of play and drive on. It’s not unusual for me to test fit two or three wrenches before I select one for a particular job. Remember, you use a long handle or breaker bar to REMOVE a tight nut and a torque wrench to INSTALL one. Forty-five to 55 ft-lb is a good range for installation, and shims can be employed on nuts that need to be timed for gas tube clearance. Let’s look at a few current offerings.

From Real Avid comes their Master-fit A2 Crowfoot wrench set for AR-15s. This would be a good starter package if you’re tooling up to work on AR-15s. The set includes a ratcheting 10 to 150 ft-lb, 1/2-inch drive torque wrench and four wrench heads: one to fit standard barrel nuts, one to fit some free float barrel nuts, a 3/4-inch wrench for muzzle devices and a 5/8-inch wrench for rifle buffer tubes. The wrench heads are the crowfoot type that support two thirds of the nut while still leaving an opening for the barrel. Ideally, a big socket would be used for barrel nuts, but that is impossible with the barrel protruding through the nut. A crowfoot wrench is somewhat like a socket with an opening cut in one side. Armorers sure have it good these days with kits like this. Always remember to back off the torque setting before storing a torque wrench to preserve calibration.

Also from Real Avid is their Armorer’s Master Wrench, which is sort of a big multi tool for AR armorers. It serves as a barrel nut wrench, hammer (with interchangeable nylon, brass and rubber heads), castle nut wrench, fixed stock receiver extension wrench and muzzle device tightener. This would be a great item to throw in your range box if you test fire AR-15 platform rifles away from your shop. As a gunsmith who frequently runs to the range to function test rifles, I will be putting one of these in my truck.

Using a Real Avid Crowfoot wrench (Right) to remove a tight nut on a match rifle with a float tube. The massive head of the 2 Unique barrel nut (Left) wrench sports nine pins.

From 2 Unique, LLC comes a wrench I’ve been using for a while I dubbed the “Mother of All Barrel Nut Wrenches” in a previous article. At 19-inches long and weighing two pounds, six ounces, this solid-steel, made-in-USA tool is suited for those stubborn barrel nuts that won’t budge with the usual coaxing. The wrench head is reminiscent of a G.I. barrel nut wrench but provides nine points of contact rather than just three. The handle is solidly welded to the head. They also produce the toughest castle nut wrench I have ever seen. Professional grade stuff.  

From Midwest Industries comes their Professional Armorer’s wrench. This is a typical double ended barrel nut/castle nut wrench that is manufactured from 4140 steel and includes wrench heads for G.I.-style and MI barrel nuts along with a castle nut driver, rifle buffer tube wrench, hammer head, muzzle device wrench, 1/2-inch drive torque wrench sockets on both ends and even a bottle opener. 100% made in the USA with a lifetime warranty. Torque specs are engraved on the handle.

Castle Nut Wrenches

There are some good standalone castle nut wrenches out there. My favorite is the aforementioned heavy-duty wrench from 2 Unique LLC, but sometimes when dealing with various end plates a different approach is required. A wrench head may be more appropriate if you wish to torque the nut, and Real Avid provides one of those in their Masterfit wrench set. An interesting one from Forward Control Design is their JCW or Joint Castle Nut Wrench which is a combination two or three lug design with a square drive hole for only $35. And, after you torque the nut don’t forget to stake it to the end plate. Forward Control Design can provide an excellent staking punch.

Gas Key Staking

What if your pet AR-15 suddenly starts to short cycle? The problem could be caused by a loose gas block, worn gas tube or loose bolt carrier key. I’ve seen carrier keys loosen in competition. Some people say that simply using thread locker on carrier key screws will work. No. I believe in thread locker AND staking keys. You’re not going to do this with a punch and hammer. You need a fixture that will hold the carrier securely while the screws are staked. The first and only fixture I ever used for this purpose was the MOACKS (Mother of All Carrier Key Stakers) from Michiguns. It is basically a block that is mounted in a vise holding the carrier while four hardened screws are tightened to stake the screws. Very fast and efficient. My original tool is slightly different from the current offerings, but they are all similar. Brownell’s also offers a staking tool which is functionally similar to MOACKS. Made in USA. Always remember that Brownell’s guarantees products they sell and if you’re unhappy with a purchase they will take it back. I have personally tested their return policy and it works.

If you have any thoughts or comments on this article, we’d love to hear them. Email us at [email protected].

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