Maximizing The AR-15

The AR-15 was never meant to be a target rifle, having been designed by Eugene Stoner for battlefield use. Previous U. S. service rifles were difficult to work on, required special tools, and a training period for military armorers that was long and difficult. Stoner corrected a lot of that. With two halves held together by captive pins, AR-15s can share one lower with uppers dedicated to self defense, hunting, target shooting, or other uses.

Barrels can be replaced quickly with a minimum of tools and armorer skill. Bolt carrier assemblies can usually be swapped as needed as it only takes minutes to check headspace with Go/No- Go gauges and I have yet to have a single Stoner rifle fail to pass. Unfortunately, these useful characteristics limit the rifle’s ability to shoot really tight groups. Fortunately, the design shoots better than it has a right to.

Part of the problem is a lack of accuracy influence from a conventional stock as was the case with previous rifles. While Stoner corrected problems found in firearms with wooden stocks, he failed to correct the attachment of the front sling swivel to the barrel. Soldiers, hunters, and competitive marksmen can benefit their shooting with sling support but that benefit is hampered when sling tension bends the barrel.

This isn’t caused by the sling swivel itself, just when tension is applied with a sling, such as it will when used for support during shooting. This tension problem is cured with a float tube, an improvement on Stoner’s design. Service Rifle competition uses modified handguards to retain an as-issued look. These tubes can add a fair amount of weight, which can be good or bad depending on the rifle’s purpose.

Geissele Automatics makes another popular handguard for Service Rifle that’s ventilated for enhanced barrel cooling. Match Rifle, F-Class, and tactical rifles have a plethora of options doing the same thing and allowing attachment of various sights, bipods, lights, and other accessories. All of these relieve pressure from the barrel and have proliferated in recent years. A poor trigger also leads to lessthan-stellar shooter performance. M16 triggers as Stoner designed are stout but repeatable.

When the military decided to limit full auto and redesigned the trigger to fire threeround bursts it created an over-engineered marksmanship nightmare with a clockwork-looking cam with teeth yielding three distinctly different trigger pulls. Outside of the military and Service Conditions matches, only NFA Class III shooters opting for the burst option have to deal with this.

Better options such as from Geissele Automatics and the Wisconsin Trigger Company (makers of the new version of the Milazzo-Krieger design) help. Research the appropriate match rules for minimum trigger pull and any other restrictions. Barrel break-in and barrel cleaning also influence accuracy potential. Done properly, break-ins make cleaning easier leading to less mess and potential for damage. Checking magazines is also important as they can influence point of impact. Sights are obviously critical.

The issue A2 sight

Rails allow attachment of various sights, etc. is pretty good and usually repeatable. Some competition shooters want finer adjustments, most easily accomplished by replacing the stock parts with ones having finer threads. Issue apertures are too big for some younger shooters and too small for more senior folks. These can also be replaced. My sight parts are from White Oak Arms. Owner John Holliger is an accomplished competitive shooter and I believe he knows more about AR sights than anyone else.

Gunsmiths need a sight checker, such as the Ray-Vin Rear Sight Verifier, that clamps on and click adjustments in the sight. I check tracking of every sight that comes into my shop. Replacing worn out sight parts was probably my number one repair job as a former military team armorer. Recent rule changes by the Civilian Marksmanship Program and National Rifle Association allowing optics has seen a decline in iron sight use at these matches along with demand for A2 uppers and integral iron sights.

March and Nightforce are the early optic sight favorites. These combined with properly set up 90 grain loads may end the long stagnation of the AR-15 and rocket shooters to new levels of marksmanship excellence. As I’ve mentioned before, I spent a number of years with the Army Reserve Marksman ship Program as a competitor and armorer. Most civilians imagine all military shooting teams have deep financial pockets, however, the Army Reserve was always the poor kid on the block with a low purchase budget.

I had to find ways to improve accuracy performance with a tight purse. Most of my fixes are either inexpensive or can be done at no cost and don’t require expensive tooling. Some of this tuning does require range time and actual shooting skills. While some gunsmith may shun detailed live-fire testing, if you’re working with a good shooter serious about optimal performance, the onus of the range testing can fall to him. These methods aren’t a "how to do it" essay but more of a "what to do" guide and overview.

I’ve covered topics under each of the subheadings in other articles in depth if you require greater detail. If you lack a particular issue with an article the interests you and can’t obtain a copy, email me at and I’ll help you. Also, if you’re at Camp Perry during They remove sling tension from the barrel and are better ventilated to aid barrel cooling. The same gauge will also check windage. the CMP National Service Rifle Matches visit me on Commercial Row at Building 910-A.

Upper/Lower Fit In "The Accu-Wedge" (April 2017) I recount my initial tests with the USAR Team uppers. Using the same Colt AR-15 in a machine rest, I rated the upper-to-lower fit as "average" tightness. The results were horrible! Average ten-shot groups with match-grade 77 grain ammo were in excess of MOA. I didn’t initially use an Accu-Wedge but did part way through the test.

Resting the exact same equipment and ammunition, adding that $5 piece of red bubble gum resulted in an enormous 26% average reduction in group size! I have never tested or fired an AR without a fresh, tightly-fitted Accu- Wedge in place since!

My machine rest grips the lower firmly while also securing the upper. With everything tightened down you’d swear there couldn’t possibly be any movement, yet an Accu-Wedge allowed significant improvement. Considering the potential improvement gained when the upper and lower are contained in a machine rest, you can well imagine how much an Accu-Wedge can help when held and fired from the shoulder.

You’ll never achieve maximum possible accuracy with a Stoner rifle with a loose upper to lower fit no matter how much money and effort you invest on other improvements. In addition, there are two pins holding these rifles together. The influence of the Accu-Wedge is exerted on the rear pin, however, both pins need to be tightened for best results. Use either thin shim stock (shown) or a BAT Machine Barrel Extension in conjunction with green Loctite.

Below center: Automotive tubing bender is used to help align the gas tube. Premium Barrel The barrel is the foundation of any firearm and AR-15 gunsmiths must make the effort to harvest all the potential accuracy the barrel maker built in. In "Barrels For Custom AR- 15s" I noted that almost every custom barrel manufacturer makes a really good barrel, sometimes. However, they do so at widely varying rates.

Some barrel companies only produce one really good barrel in ten while other makers go as high as eight in nine. That is a huge spread in quality and it behooves custom gun makers to hedge their bets by purchasing from those makers on the high end. Based on my tests, the two custom makers consistently producing the highest ratio of exceptional barrels are Bartlein and Krieger. Both use a single point cut rifling method coupled with quality steel, meticulous workmanship, and good tooling.

Don’t overlook chrome-moly steel as stainless is sometimes overrated. Consider gain twist rifling for applications that warrant it as these are more readily available now. For more information, see "Revisiting Gain Twist" (November and December 2013) and "Gain Twist Barrels For Palma" (December 2016). Stabilize Barrel Extensions "The Relationship Of Barrel Extension Diameter To Accuracy In The AR-15" (March and April 2013) was the first topic I discussed in this magazine.

I explained how the barrel fits in the upper receiver and how the barrel nut holds it captive. While the mounting system is simple and easy, it results in a lot of movement in the back of the barrel. One cure uses thin shim stock and the second a custom oversized BAT Machine match barrel extension. Both are locked in with green Loctite. Done properly, these will cut groups about a third.

Gas Tube Alignment Very few gas tubes will be correctly in line with the bolt carrier key without about 15 minutes of extra fine tuning. Getting this right will not only tighten groups but

From front to rear, Young Manufacturing, JP Enterprises, Les Baer. Expect an 8.8% average reduction in group size. Add anti-tilt pads to these carriers and enjoy another 14% group shrinkage. This provides improved support to the rear of the barrel extension. will minimize fliers. The only tool needed is a tubing bender available at auto parts stores. For more information, see "Gas Tube Alignment" (March 2014).

Chamber Selection There is a lot of encyclopedic error circulated about how jumping magazine-length ammo long distances before entering the rifling won’t create accuracy problems The very assertion is false! In "AR-15 Chamber Selection" (July-September 2014) discusses the ideal chamber that is best for your customer’s needs. Match Bolt Carriers If you are building anew rifle or upper you have to purchase a bolt carrier anyway.

Why not spend a few extra bucks and buy a match carrier that gives more consistent lock ups? There are three brands of match carriers that work well available in black or stainless finish. Average reduction in group size will be 8.8% as detailed in "AR-15 Upper Quick Fixes: Match Bolt Carriers" (May 2014). Anti-Tilt Pads With so much slop between the carrier and upper receiver, the back of the carrier can tilt down. This throws the bolt face out of perpendicular to the axis of the bore.

Gunsmiths knew about this when the AR-15 was first released. Some tried to correct it but function can be impaired, so everybody buried their heads in the sand for decades and tried to make believe the problem didn’t even exist. In "Combating AR- 15 Bolt Carrier Tilt" (May 2017) I offered a couple of cheap and quick solutions and suggested that mine are baby steps. Use whatever method your own ingenuity comes up with to correct the problem.

Significant accuracy gains can result to about a 14% reduction in group sizes based on my study. Some stock bolt carriers are candidates for anti-tilt pads if the customer doesn’t wish to invest in anew match carrier. Barrel Harmonics I detailed good ways to tune this in "AR-15 Barrel Harmonics" (October 2016). Unfortunately, in order to properly influence harmonics someone must spend time shooting groups and making changes in pressures and angles applied to the barrel.

While none of this is difficult it does require shooting skill or a machine rest with expertise in its use. Many gunsmiths will want to encourage the shooter to perform their own range testing. Done properly, accuracy gain can be expected to be about 20%. Heavy Upper Receivers These are currently available as the DPMS Lo-Pro and Sun Devil Heavy- Walled Billet Receiver. Both are flat tops. The Lo-Pro comes without either a dust cover or forward bolt assist and is made to be mounted on regular lower receivers.

The Sun Devil is available with any combination of dust covers and forward assists and looks best when mounted on their matching heavy-walled lower but will fit regular lowers as well. The advantage to the heavy walls is they provide better support to the back 2/3 of the barrel

extension that lives behind the barrel nut threads. Barrel extensions still must be fitted to these receivers the same as conventional skinny ones. Check match rules as these are not legal in Service Rifle events. Cryogenic/Fire Lapping Both of these are last ditch efforts to fix sick barrels. Cryo was covered in "AR-15 Barrel Treatments For Maximum Precision" (September 2016).

My records show applying cryo to under-performing barrels resulted in a 9.4% average reduction in group size but does nothing for healthy barrels. "Electropolishing & Fire Lapping" (May 2015) discussed how I On right, the rounds outlined in the square at 4 o’clock and 6 o’clock just outside the group were the first and second fouling shots after cleaning. ) on bores when storing firearms, even for short periods.

These reduce cleaning rod damage to paper-thin lands. fire lapped about 100 sick barrels for an average accuracy gain of 19.3%. I do not recommend proactive application of this process to healthy barrels. I have not used either treatment in about a decade since I concluded my massive barrel accuracy study and began purchasing barrels from only Krieger and Bartlein. My mind set is that it’s best to purchase a quality barrel already capable of sub-minute groups without performing work arounds.

The next tips are on the shooter to perform. Here is a to-do list to provide your customers. Bore/Carrier Cleaning The bolt carrier assembly and bore need to be cleaned every time the gun is fired unless you are using it as a hunting rifle firing one or two rounds a day. Of the two, bolt carrier cleaning is more straight forward. Most gunsmiths will want an ultrasonic cleaner for this. Lacking such a unit, shop rags work fine.

Most ultrasonic cleaners use solvent with water in it so let the parts dry thoroughly before running through a second time with the manufacturer recommended lubricant. These lubricants work better to prevent rust than to actually lubricate so I always finish with regular gun oil and add oil to the bolt rings during range sessions as they dry out fast. Anti-tilt pads require daily lube and I like something thicker, such as Tetra Gun Grease. Bore cleaning is damned if you do and damned if you don’t.

On the one hand, you are damned for cleaning as there’s risk of damaging the delicate, paper-thin lands due to cleaning rod flex. Cleaning must remove baked-on carbon and copper fouling and these require different methods to remove. Most of the worry goes to copper fouling but it’s easier remove and less likely to damage to the bore. There are plenty of good copper solvents on the market, just follow the manufacturer’s instructions. Many copper solvents result in a greenish or bluish coloration to the patches.

Cleaning until patches no longer have these colors is a fair indication the copper is gone. Carbon fouling is more difficult to get out. Lacking a bore scope, it’s difficult to know when you have removed it all. Solvents don’t a discoloration with carbon and I don’t know of a solvent, incantation, or snake oil that reliably removes it. Carbon fouling requires an abrasive for removal and that is where we get in trouble. It is not the abrasives themselves so much as the back and forth scrubbing with a bore brush.

Being fatter than the lands and

Stop when your index finger hits the leading edge of the ejection port. grooves (anew bore brush typically measures 0.235" for a .22 centerfire with 0.218-0.219" lands and 0.224" grooves) there is quite a bit of resistance, causing the cleaning rod to flex and scrape into the easilydamaged lands. Bore guides help keep the rod straight but aren’t fool proof. J-B Bore Cleaning Compound is a common abrasive used on a patch for fouling removal.

The direction of the patch is actually changed inside the bore before the patch can exit the muzzle and this reversing of the patch can cause significant rod flex and resultant bore damage. You are also damned by failing to clean the bore as accuracy will suffer. Each barrel differs as to how many rounds or how severe.

I had a customer bring in an upper at the end of a shooting season to reset 308 and .223 long range loads in full-value cross winds. bullet seating depth and update the sweet spot to compensate for throat erosion. The customer had been letting the bore soak overnight with Hoppe’s Bench Rest as per the directions. My bore scope revealed no copper fouling but I could see some remaining carbon fouling at the back third of the barrel.

Not severe but enough that I recommended using a few more brush strokes on each cleaning. I decided to perform a machine rest test to find out the importance of getting the carbon out. The test targets revealed a very significant 47% reduction in group size clearly brought about by the removal of the carbon fouling. I had used J-B short stroked back and forth in the rear third of the barrel and let the bore soak in between applications.

Each time I ended up with several patches showing copper fouling finally removed after being laid down and covered by carbon in layers over many shooting sessions. People have maintained fouling can be layered over time and I believe it. When patches of Hoppe’s proved the copper was gone, I went back to another session with J-B to remove the next layer of carbon and another soak of Bench Rest revealed more copper. When the bore was finally truly clean it shot a much tighter sub-minute group.

Another cleaning topic is salt bath nitriding, such as Isonite or Melonite. It works both on stainless and chrome-moly steel and differs from regular bluing because the salt bath coats both the inside of the bore and the outside of the barrel. I have tested the process extensively. It has no negative impact on accuracy or velocity and makes cleaning much easier. More frequent cleaning with and easy-to-clean bore means damage is much less likely.

The bore should still be coated with a corrosion inhibitor, such burnishing with WD-40 or Boe Shield T-9 prior to storage. Caution: If you plan to send a barrel off to be nitrided, read "Retention Of AR-15 Barrel Extensions" (September 2013). The nitriding process is performed at very high temperatures and can cause your barrel to unscrew from the extension later on. The article will detail two very good ways to avoid this problem.

Concentricity Management Getting the bullet lined up perfectly with the center axis of the bore has been known for decades and is practiced religiously in some precision shooting disciplines. Un-

fortunately, AR-15 shooters seem to have migrated away from the practice. Compared to the M14, AR-15s are much more accurate. I think shooters have taken some things for granted and sometime get careless with their ammunition concentricity. This is unfortunate because barrel makers and gunsmiths can’t build a rifle that will shoot crooked ammo well. Managing concentricity is fast, easy, and cheap and will improve performance. See "Better Ammunition" (April 2016) for details.

Outside Neck Turning Another ammunition topic in the same article, some shooters perform neck thickness uniforming in an attempt at more concentric ammo. More uniform case necks can improve accuracy by helping line up the bullet straighter with the axis of the body of the casing. Case necks that are fatter on one side hold the bullet at the moment of firing differently. The thick side of the neck will be more tenacious and tend to let go of the bullet less than thinner section.

Even with the bullet seated straight it can tip a little going into the throat. Shaving off areas of thick brass from case necks during the neck turning process helps eliminate some of this tipping. However, neck turning is gun specific. Some guns really benefit while others don’t. I think that the dimensions of chamber necks have a lot of vote in this. Chambers with tighter necks seem to like the neck turning process more so than chambers with overly fat necks.

Case Forming Concentricity has to do with getting the bullet lined up in the center of the case neck. A related topic involves getting the whole cartridge properly lined up in the chamber itself. This is best accomplished by fire forming brass in the specific chamber and then neck sizing and bumping the shoulder back a little during the loading process. The case body isn’t touched and this eliminates accuracy-robbing slop in the chamber. Such around will center in the chamber much better.

Expect an average reduction in group size of about 16% when using this technique. For reliability sake, this technique is mostly reserved for shooting situations where single rounds are hand fed into the chamber. Full-length resize for magazinefed ammunition. Also, when feeding singles shove each round to the same point up into the chamber each time. This will uniformly position each round and result in more consistent velocities and a 13.8% average tighter groups for no extra real work.

Bullet Seating Sweet Spot This also is best with hand-fed cartridges and requires load development with range testing. It takes me about half a day with a machine rest to arrive at the exact seating length to hit a firearm’s sweet spot. The improvement to accuracy, especially when combined with the previously discussed ammo topics, can be astonishing. Expect about a 20% average reduction in group size.

I do this for every firearm I build or rebarrel and the customer gets sample rounds that he can measure and set up his die to duplicate the exact length. This custom seating length combines well with other hand loading tailoring such as varying powders and charge weight to produce optimal accuracy. More details are in "Bullet Seating Sweet Spot" (June 2016). 90 Grain Bullets 90 grain bullets are the next logical step in the evolution of the AR- 15.

They first came on the market around 2004 and, like any new bullet, took about a decade to work the kinks out. For those shooting long range slow fire disciplines, 90 grain bullets are the ticket. In equal length barrels, 90s fight wind drift as efficiently as anything you can load in a .308 for fraction of the recoil and expense. This creates from about 17% (with the Berger boat tail and its 0.512 ballistic coefficient) to 24% (with the improved second generation Sierra Match King and its 0.563 B.

C.) of "wind proofing" over popular 80 grain options with a B. C. of 0.420. 90 grain .224 bullets shoot about 7.7% tighter groups with half the fliers and of less severity than the 80s. These gains assume the rifle is barreled with the stellar Bartlein 5R gain twist (1:13-1:6.5) having 0.218" lands and 0.2245" grooves. Chromemoly steel is preferred. What’s not to like about those statistics? Detailed information is in "Building The 90 Grain AR-15" (April-May 2014).

I also suggest going to Bartlein’s website (BartleinBarrels.com) and read their testimonials. At the time of this writing, everyone featured shoots Service Rifle using this gain twist/90 grain combination. Customers should consider making the switch and achieving similar marksmanship excellence to get their pictures placed on the website next.

Marksmanship I have saved the most difficult shooter’s task for last. All of our work as gunsmiths and all of the shooter’s work on preparation goes into the dumpster if the shooter makes marksmanship errors. We are trying to build guns that guarantee holding to the Xring will keep a bullet inside there. That same guarantee holds, unfortunately, if the shooter points into the 7 ring at the moment of truth.

Many shooters want to spend extra money in the hopes that gunsmiths can make life easier for them so they don’t have to put in the tremendous effort of mastering the fundamentals of marksmanship. Unfortunately, I don’t possess a shortcut for this. If I did I would rush to the Patent Office! I provide my customers with a copy of the final test targets fired from machine rest. Given such hard evidence, it’s difficult to argue a bad shot was the fault of the gun.

Accuracy wise, the AR-15 has been on a roller coaster for about a half century. There are design features that make it shoot surprisingly well. However, accuracy stagnated in early life. Even when the A2 was adopted not much was done to get it shooting better. In fact, things like the burst cam, a 1:7 twist over-spinning bullets, and issue M855 ammunition with steel penetrators made it shoot worse!

In "Improving Rack-Grade AR- 15s" (December 2014) I mentioned how Derrick Martin with the National Guard and I with the Army Reserve both found that 1:9 twist shoots green tip much better. I even tested 1:10 with good accuracy. We made those discoveries a quarter century ago. When the Army Marksmanship Unit and individuals like Bill Wylde, Albert Turner, and Frank White became interested in improving ARs, several innovations took place.

Float tubes removed barrel pressure, improved triggers from people like Charlie Milazzo and Bill Geissele, and true match bullets from Sierra, starting with their 69 grain Match King. Heavy premium barrels with an appropriate twist filled out the rest of the bill. Sierra soon released their 77 grain SMK, still magazine-length but with improved ballistic coefficient. The 80 grain SMK seated longer than magazine length but improved long range capability a bunch.

Twist rates had to go back up a bit to stabilize these longer bullets and chambers were adjusted by increasing free bore. In my opinion, some of that free bore got carried away and actually compromises the performance of magazine-length ammo and the life of the barrel to this day. The rear sight improved a little as clicks were made finer and a single pin was added to the front to aid in tracking. When a second pin was added at the back, a "double pinned" rear became the new standard.

The AMU took the lead along with John Holliger at White Oak. However, after that all too brief surge, the design stagnated for a period. I guess guys thought that it was as good as it was going to get. I often compare the AR- 15 to my 1966 Dodge Charger as they were born about the same time period. The Charger was equipped with a four-barrel carburetor, manual window operation, an AM-only radio, and no air conditioning. Average sticker price was around $3,100! Compare that to features common today.

Automotive designers and mechanics have not been afraid to redesign and improve, nor was the auto industry afraid to risk failure. Are we collectively risking failure with firearm designs? I assure you not everything I have tried has resulted in improved accuracy. In fact, "AR-15 Build Problems" (May 2016) chronicles some of those mistrials. During a two-decade hiatus while other gunsmiths were reluctant to innovate, I was happy to experiment for the Army Reserve.

I borrowed, dusted off, perfected, polished, and sometime invented affordable, effective, and easy techniques that worked. In 2006 I also started working with bullet and barrel manufacturers to push performance further with 90 grain bullets. With Sierra’s successful second generation 90 grain Match King my research in that arena is finished. This makes for a 90 grain long range bullet that’s easy to get, to handload, totally reliable, and really bucks sudden wind changes.

Using the methods and parts detailed in this article I was able to fully cut in half the average group sizes of my Team’s uppers. When I came on board only 37 out of 135 of the uppers I inherited would shoot ten-shot groups to an honest one MOA in a state-of-the-art machine rest. When I left every single upper could shoot that well. Most of this work is simple enough.

As you read through the supporting articles ask, "Why didn’t somebody think of this stuff forty years sooner?" If you employ the tips in this article there is no reason you can’t cut your group sizes in half and achieve true sub-minute groups as well. Most of the work is easy to do, not all that time consuming, and relatively cheap. AG