In our Shooters’ Forum, one member recently asked: “What makes an AR accurate? What parts on an AR can really affect accuracy — such as free-floating handguards, barrels, bolts, bolt carriers?” He wanted an honest, well-informed answer, not just sales pitches. Robert Whitley posted a very comprehensive answer to this question, based on his experience building and testing dozens of AR-platform rifles. Robert runs AR-X Enterprises, which produces match-grade uppers for High Power competitors, tactical shooters, and varminters.
Building an Accurate AR — What is Most Important
by Robert Whitley
There are a lot of things that can be done to an AR to enhance consistent accuracy, and I use the words “consistent accuracy” because consistency is a part of it (i.e. plenty of guns will give a couple great 5-shot groups, but won’t do a very good 10- or 20-shot groups, and some guns will shoot great one day and not so good on others).
Here are things we think are important to accuracy.
1. Great Barrel: You’ll want a premium match-grade barrel, well-machined with a good crown and a match-type chambering, true to the bore and well cut. The extension threads must also be cut true to the bore, with everything true and in proper alignment.
2. Rigid Upper: A rigid, heavy-walled upper receiver aids accuracy. The typical AR upper receiver was made for a lightweight carry rifle and they stripped all the metal they could off it to make it light to carry (which is advantageous for the military). The net result are upper receivers that are so thin you can flex them with your bare hands. These flexible uppers are “strong enough” for general use, but they are not ideal for accuracy. Accuracy improves with a more rigid upper receiver.
3. True Receiver Face: We’ve found that truing the receiver face is valuable. Some may argue this point but it is always best to keep everything related to the barrel and the bore in complete alignment with the bore (i.e. barrel extension, bolt, upper receiver, carrier, etc.).
4. Barrel Extension: You should Loctite or glue the barrel extension into the upper receiver. This holds it in place all the way front to back in the upper receiver. Otherwise if there is any play (and there typically is) it just hangs on the face of the upper receiver completely dependent on the face of the upper receiver as the sole source of support for the barrel as opposed to being made more an integral part of the upper receiver by being glued-in.
5. Gas Block: You want a gas block that does not impose pointed stress on the barrel. Clamp-on types that grab all the way around the barrel are excellent. The blocks that are pinned on with tapered pins that wedge against the barrel or the slip on type of block with set screws that push up from underneath (or directly on the barrel) can deform the bore inside of the barrel and can wreck the accuracy of an otherwise great barrel.
6. Free-Float Handguard: A rigid, free-float handguard (and I emphasize the word rigid) really makes a difference. There are many types of free-float handguards and a free-float handguard is, in and of itself, a huge improvement over a non-free-float set up, but best is a rigid set-up. Some of the ones on the market are small diameter, thin and/or flexible and if you are shooting off any type of rest, bipod, front bag, etc., a rigid fore-end is best since ARs want to jump, bounce and twist when you let a shot go, as the carrier starts to begin its cycle before the bullet exits the bore.
7. Barrel Contour: You want some meat on the barrel. Between the upper receiver and the gas block don’t go real thin with a barrel (we like 1″ diameter if it’s workable weight-wise). When you touch off a round and the bullet passes the gas port, the gas system immediately starts pressuring up with a gas impulse that provides vibrations and stress on the barrel, especially between the gas block back to the receiver. A heavier barrel here dampens that. Staying a little heavier with barrel contour through the gas block area and out to the muzzle is good for the same reasons. ARs have a lot going on when you touch off a round and the gas system pressures up and the carrier starts moving (all before the bullet exits the bore) so the more things are made heavier and rigid to counteract that the better — within reason (I’m not advocating a 12-lb barrel).
8. Gas Tube Routing Clearance: You want a gas tube that runs freely through the barrel nut, through the front of the upper receiver, and through the gas key in the carrier. Ensure the gas tube is not impinged by any of them, so that it does not load the carrier in a stressed orientation. You don’t want the gas tube bound up so that when the gas tube pressures up it immediately wants to transmit more force and impulse to the barrel than would normally occur. We sometimes spend a lot of time moving the gas block with gas tube on and off new build uppers and tweaking gas tubes to get proper clearance and alignment. Most gas tubes do need a little “tweaking” to get them right — factory tubes may work OK but they typically do not function optimally without hand-fitting.
9. Gas Port Tuning: You want to avoid over-porting the gas port. Being over-gassed makes the gas system pressure up earlier and more aggressively. This causes more impulse, and increases forces and vibration affecting the top end and the barrel. Tune the gas port to give the amount of pressure needed to function properly and adequately but no more.
10. Front/Back Bolt Play: If accuracy is the game, don’t leave a lot of front/back bolt play (keep it .003″ but no more than .005″). We’ve seen factory rifles run .012″ to .015″ play, which is OK if you need to leave room for dirt and grime in a military application. However, that amount of play is not ideal for a high-accuracy AR build. A lot of front/back bolt play allows rounds to be hammered into the chamber and actually re-formed in a non-consistent way, as they are loaded into the chamber.
11. Component Quality: Use good parts from a reputable source and be wary of “gun show specials”. All parts are NOT the same. Some are good, some are not so good, and some aftermarket parts are simply bad. Don’t be afraid to use mil-spec-type carriers; by and large they are excellent for an accuracy build. Also, remember that just because a carrier says “National Match” or something else on it does not necessarily mean it’s any better. Be wary of chrome-plated parts as the chrome plating can change the parts dimensionally and can also make it hard to do hand-fitting for fit and function.
12. Upper to Lower Fit: A good upper/lower fit is helpful. For quick and dirty fit enhancement, an Accu-Wedge in the rear helps a lot. The ultimate solution is to bed the upper to a specific lower so that the upper and lower, when together, are more like one integral unit. For the upper receivers we produce, we try to get the specs as close as we can, but still fit the various lowers in the market place.
13. Muzzle Attachments: Don’t screw up the muzzle (literally). Leave as much metal on the barrel at the muzzle as you can. People like to thread the muzzle for a flash hider, suppressor, muzzle brake, or some other attachment, but if you really want accuracy, leave as much metal as you can there. And, if you have something that screws on, set it up so that it can be put on and have it stay there without putting a lot of torque and stress on it right where the bullet exits the bore. If you are going to thread the end of the barrel, make it concentric with the bore and make sure what you screw on there is as well. For all muzzle attachments, also ensure that the holes through which the bullet passes through are dead true to the bore. Many aftermarket screw-on things are not so good that way. Anything that vents gas should vent symmetrically (i.e. if it vents left, it should vent equally right, and likewise, if it vents up, it should vent down equally). Uneven venting of gas can wreck accuracy.
14. Quality Ammunition: Ammo is a whole story by itself, but loads that are too hot typically shoot poorly in an AR-15. If you want accuracy out of an AR-15, avoid overly hot loads. Shown below are test groups shot with four (4) different uppers, all with moderate loads. These four uppers all pretty much had the same features and things done to them as explained in this article, and they all shot great.
Here is a very interesting rifle, a true metal/wood hybrid that combines an aluminum front section with figured walnut in the rear half. As you can see, this unique rifle also features a barrel block that allows the Savage action to float. You may be wondering “how is the metal section connected to the wood?” The gun’s owner/builder epoxied a stainless steel tube in the wood and that tube is secured in the aluminum fore-end with set screws.
Forum member Justin V. reports: “Sometime last fall my buddy wanted to build barrel-blocked Bavage. He is a machinist by trade so he was able to build all of the custom components himself. I know he put a ton of time into this thing over the winter, taking his time to get it done right. If you shoot in Cadillac or Midland, Michigan you will probably see him around. He tried to shoot a match this past weekend but was rained out. Hopefully it will stop raining in Michigan so he can see what it can do at 600 yards. Here are the results….” Learn more about this gun in this FORUM Thread.
Brownells’ Do-It-Yourself (DIY) video series provides logical, step-by-step installation help for triggers, stocks, and springs. Nine separate videos cover Brownells various DIY Kits. Not sure if you’re up to the project? Just watch each video to see what’s involved. The nine DIY kits are:
Some folks think you need a new (or nearly-new) barrel to win a benchrest match. That may be true in the centerfire game, but in the world of rimfire benchrest, things are different. Good barrels can remain accurate for a long, long time. That was demonstrated by our friend Joe Friedrich who recently set a new ARA 4-target Aggregate record. Joe was shooting his trusty old “Sweet Pea” rifle with a very well-worn barrel. In fact, Joe’s record-setting Benchmark barrel has logged well over 100,000 rounds. That’s right, a barrel with over 100K rounds shot the best 4-target ARA Agg ever. Will wonders never cease…
In this video, Joe talks about his rifle, the amazing longevity of his Benchmark barrel, and the ELEY ammo he used to shoot two 2500s on the same day (with a 2475 average for four targets):
Here are exclusive “Spy Shots” of a soon-to-be released project, the all-new F-Open chassis system from Competition Machine (Gary Eliseo). Dubbed the “F1″ stock by Gary, this radical new chassis system is designed expressly for F-Open competition. With a super-low Center of Gravity (COG), the F1 boasts many innovative features including an epoxy-lined barrel block that allows the action to float. The F1’s length-of-pull is adjustable for length while the buttpad holder adjusts for height.
The stock, which will work with any type of action, should sell for about the same price as a fully-adjustable fiberglass stock. Competition Machine hopes to start shipping F1 stocks in summer 2015.
The F1 stock will accept any action, long or short, right-hand or left-hand. The F1 is shown below with a Pierce magnum long action.
There’s a great new way to apply an eye-catching finish to fiberglass and synthetic stocks. Water Transfer Printing (aka Hydro-Dipping) can apply beautiful, stylized patterns to your stock, and the process costs less than a custom paint job. Hydro-dipping is ideal for applying amazing photo-realistic effects such as stone, wood burl, snakeskin, or faux carbon fiber. Hydro-dipping requires no harsh chemicals or high heat so there are no negative side effects. You just end up with an amazing, patterned finish on your stock.
Hundreds of different patterns are available. We like the carbon-look finish on benchrest guns and the snakeskin patterns on hunting and varmint rifles. Natural snakeskin designs, in this Editor’s opinion, are the most effective camouflage for the largely arrid backcountry in the American southwest.
Here’s some eye candy for the tactical guys out there. George Gardner of G.A. Precision sent us some images of a cool tactical rifle. GAP fitted a Bartlein barrel to a Stiller TAC 30 action. The barreled action was placed in a J. Allen Enterprises JAE-700 modular stock by Performance Arms of Witchita, Kansas. On top is a U.S. Optics SN-3 scope in Badger rings, with an Atlas Bipod up front. Very nice rig, and the JAE-700 has some nice options installed, including an adjustable palm rest and rear mono-pod.
Even in the “tactical” world, hand craftsmanship is not dead yet. Chad Dixon of Long Rifles Inc. (LRI) is building the lastest Sniper’s Hide Cup Trophy Rifle. These photos show the exquisite stock crafted by Chad and Jesse Kaufman of Black Hills Gunstocks & Engraving. Chad cut the stock on his CNC mill and Jesse did the final sanding and finishing on the wood. Here’s what master craftsman Kaufman had to say about the project: “We delivered the Long Rifles Inc. Mausingfield today! I was so very pleased that Chad and the staff at the shop thought it looked great. It means a lot to be able to support my family and household with the income I receive from my labor. May the Lord bless you all. — Jesse.”
In our Shooters’ Forum, there is an interesting thread showcasing a number of new varmint rifles built for the 2015 season. Here are six of the noteworthy builds highlighted in the thread. See more rifles in this Forum thread: Let’s See Your New For 2015 Rigs.
From member Greg T
6mm AI on RBLP Bat Three-Lug Action
Krieger 1:14″-Twist, 28″ Tube
.274 Neck throated for 75 gr V-Max
Blue / Black Shurley Brothers Lowrider Stock
Comment: I think I have found my favorite caliber as now I basically have twins – one for 87 grainers and one for 75 grainers. Yes this is overkill (and financially not the best decision) but it’s fun, so what the heck. With such a slow twist rate, I think I can push the 75s to 3850 fps or so.
This is one amazing .50-caliber rifle. Along with the lever-actuated falling block, it has a massive swing-out breech block like you’d find on a field artillery piece. The action is so wide that the sights and scope are offset. You’ve heard of the “Beauty and the Beast”? Well here the Beast IS a Beauty….
View looking down at the action from above. Note the hinged Breech-Block.
You have to love it when a prototype product not only performs well, but actually wins a match. For some time, Criterion Barrels has been working on a match-grade barrel for vintage Lee-Enfield rifles. It looks like they got things right…
Over the Easter weekend the New Zealand Service Rifle Association held its annual national service rifle competition. Coming first in the Classic Bolt Action class was Wellington’s Nicole McKee shooting a Lee-Enfield with a new, prototype Criterion barrel. Nicole’s rifle was built by her husband Duncan, a vintage rifle expert who specializes in accurizing the No. 4 and SMLE actions. Nicole’s .303 British handloads featured Hornady 174gr FMJ Boattail bullets (SKU: 3131) pushed by 47.0 grains of ADI 2209 (H4350). ADI 2209 has become the top go-to powder for .303 British shooters in New Zealand.
We first ran this story a couple seasons back. Since they we’ve received many questions about this gun, so we thought we’d give readers another chance to learn about this truly innovative, switch-barrel “convertible” rifle. This gun works for both short-range and long-range benchrest matches.
You interested in a really wild, innovative bench gun that can shoot both short-range and long-range matches? Check out Seb Lambang’s latest “do-it-all” rifle. It’s a switch-barrel rifle combining two very different chamberings: 6 PPC and .284 Winchester. With that caliber combo, Seb’s covered from 100 yards (LV/HV mode) all the way out to 1000 (LR Light Gun mode). But the dual chambering is not the rifle’s only trick feature. Exploiting the new long-range benchrest rules, Seb has fitted a 3″-wide, flat rear metal keel to the buttstock. That counter-balances his 30″-long 7mm barrel, improves tracking, and adds stability. Seb built the stock and smithing was done by Australian gunsmith David Kerr.
Detachable Hammerhead Wing Section Plus Fat-Bottom Keel
To further reduce torque and improve tracking, the stock features an 8″-wide, detachable fore-end fixture. This “hammerhead” fore-end section has extended “wings” on both sides, making the rifle super-stable. The hammerhead unit can be removed, leaving the stock 3″ wide for use in registered benchrest matches where 3″ is the maximum width. The photos below show Seb’s gun in .284 Win Long-Range (LR) Light Gun mode.
Here’s a tale that should make you chuckle. This is the kind of boo-boo any shooter can make (but hopefully only once). Our friend Vu Pham from Sacramento was out testing his .260 Rem tactical rifle. Now Vu, an ace NorCal Tactical marksman, is a darn good shooter — but his first three-shot, 200-yard group looked like a shotgun pattern. Vu was puzzled to say the least. (His actual reaction, as noted on the target, was “WTF?!”)
But there was a simple explanation for the rifle’s miserable accuracy — Vu forgot to tighten the crossbolts attaching the rings to his scope rail. Consequently, his scope was moving after each shot. According to Vu, stunned disbelief followed by embarrassment happens “the moment you realized you forgot to torque your scope rings to the base after moving [the scope] the night before. [I felt like a] Freaking nooooob.”
Can you list all the serious problems that excessive headspace can cause? For that matter, could you even explain what, exactly, is meant by the term “headspace”? If not, you should watch this instructional video from Brownells. This video defines the term “headspace”, explains why proper headspacing is critically important, and illustrates how headspace gauges work.
Headspace is a measurement from the bolt-face to a point in the chamber. This point of measurement will vary based on the type of cartridge. Improper headspace, either excessive or (conversely) under SAAMI specifications, can cause a variety of problems, many serious.
This video from Brownells talks about a the crown of a barrel and how the crown’s condition affects accuracy. As the bullet leaves the barrel of the gun, the shape, alignment and the condition of the crown can affect the accuracy of your shot. A proper crown is essential to ensure that the bullet leaves the barrel correctly and that the propellant gasses behind the bullet are distributed evenly on firing. A square crown without burrs and a smooth transition will normally ensure consistency from shot to shot. By contrast, a damaged crown can cause unpredictable flyers that open your group. That’s why it’s important to have perfect crowns on all your barrels.
The video explains the different types of crowns that can be used. In addition, the video shows how you can chamfer your muzzle in a home shop. If you use a properly-sized pilot, cutting a shallow chamfer is something that most guys with some mechanical skill can handle. Just be sure to use lubricant, flush chips, and don’t rush the job. Cutting the barrel is another matter. At the 1:20 mark the video shows how to use a hack-saw to remove a damaged muzzle section. While this may be fine for an inexpensive rifle that needs a “quick fix”, we do NOT recommend using a hack-saw with a vise for a competition barrel. The reason is that it is too easy for a novice to produce a cut that is not square. We suggest letting a professional gunsmith cut and crown your competition barrels.
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Here is Ernie Bishop’s pride and joy, a specialty pistol nicknamed “Batman” because the black carbon-fiber stock looks like the Batmobile. This is one sophisticated handgun. Complete with scope, the Batman pistol weighs under 7.5 pounds, thanks to the ultra-light stock. The carbon stock is 6 inches wide at the fore-end, yet weighs just one pound. Ernie tells us: “This gun shoots amazing and is easy to shoot especially with my SEB MAX Rest.” Ernie adds, “The gun will soon also have a field-usable rear-grip stock so I can shoot it prone from a bipod as well.”
Click Photo to View Larger Image
The Batman pistol is chambered for the 6mm “Long Dasher”, a 6mm 40°-shouldered variant of the 6.5×47 Lapua. Ernie loads Berger 105gr Hybrid bullets pushed by Hodgdon H-4350 powder.
The gun, crafted by Eric Wallance of Nawaka Firearms, features an XP-100 action, Jewell trigger, and 15″-long, Brux 1:8″-twist barrel with aluminum muzzle brake. Interestingly, this gun does not have a traditional recoil lug. Instead, gunsmith Wallace milled out a lug from the bottom of the XP-100 action to save weight. On top of the action, the rig carries a Sightron Inc S-III 6-24X56mm scope in Kelbly rings on a custom +20 MOA rail.
Here are three FIVE-shot groups at 500 yards, shot by Ernie’s Batman pistol:
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Manners Composite Stocks produces some of the best tactical, hunting, and competition stocks you can buy. Learn more about Tom Manners’s company in an insightful Factory Tour Story in LongRangeHunting.com. Author David Fortier recently visited Kansas City, Missouri to tour the Manners Composite Stocks factory. There, Fortier found an impressive facility, with 37 employees producing stocks under the guidance of founder Tom Manners.
The history of Manners Composite Stocks is a classic American success story of dedication and hard work. Tom Manners, a competitive long-range shooter, started producing stocks at home as a hobby. Demand for stocks rose and Tom had to finance expansion. To do that, Manners sold his beloved 427 Cobra replica to purchase a mill and compressor, and pay shop rent for a year. After that initial sacrifice, business has boomed. Tom’s dedication has been rewarded. Fortier reports:
Since he expanded from working at his home, [Tom’s] business has grown by 30 to 40 percent every year. Within five years he had outgrown the shop and secured a larger facility. Business growth has continued, and when I met with him he had just added another 4,000-square-foot building. Today he has 37 employees and runs two shifts trying to keep up with orders. Over the years, his offerings have steadily grown. Some of his biggest supporters have always been George Gardner (G.A. Precision) and Marty Bordsen (Badger Ordnance). They combined and created one of his first tactical stocks, the MCS-GAT. This stock became his first piece to be torture tested. To see just how rugged it was, he took it and put it on the arms of a chair and stood on it (USMC stock test) to try to break it. The stock shrugged off the abuse, so he used it to hit softballs, without issues. He then drove over it with a truck. When this failed to harm it, he put angle iron under each end and parked the truck on it. Despite all the abuse, it never failed and therefore the MCS-GAT caught people’s attention.”
This is the kind of family-friendly, “feel-good” story we like. Texan Richard King created a rimfire benchrest rifle using a classic Martini Mark III smallbore action. He fitted the gun with a new flat, wide forearm and a new buttstock, allowing the gun to sit steady on the bags and track smoothly. The narrow action was also fitted with a cantilevered top rail to hold a high-magnification scope.
Here is Vicki King, with Martini Mark III and her trophy.
But here’s the best part. Richard provided this updated classic to his wife Vicki, who proceded to win a rimfire benchrest match (Vintage class) with the old Martini. Richard reports: “Here is my lovely wife with her High Overall Vintage trophy. That is a Martini Mark III that I re-stocked in walnut for 50-yard, .22-caliber benchrest matches. It’s great to have her shooting with me again.” FYI, last summer Richard and Vicki celebrated their 50th wedding anniversary!
Bravo Richard — kudos to you AND to your lovely bride. It’s great to see a couple shooting together. It’s also great to see a classic rifle brought back to the winner’s circle with some inspired stock-work and other upgrades.
Here is Richard King, with his handiwork — an updated Martini Mark III smallbore rifle.
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