M16/AR15 as a Sniper or Designated Marksman Rifle
I deployed to Iraq with an infantry company that was attached to different infantry brigade. They were to supply our company with weapons and equipment, but as our deployment date came nearer, we had not received our sniper rifles. A sniper instructor recommended that I purchase a varmint upper for my M4. (At this time infantry and cavalry units of the 3rd Infantry Division and others were purchasing similar uppers from their unit funds for issue to their squad designated marksmen.) I contacted M & A Parts and ordered a Lewis Machine and Tool 20″ varmint upper, bolt and carrier, and bipod. I specified 1 in 8 twist rifling to best stabilize the 77gr. Mk 262 LR 5.56 ammunition. I purchased an IOR 2.5-10×42 tactical scope with MP8 illuminated reticle. At the time, variations of that general type of weapon were loosely designated Mk12 rifles, although the concrete specs for the current Mk12 SPR were solidifying. I have made the following observations after using this weapon system in Iraq as a company level sniper.
The M16/AR-15 based sniper weapon system is ideal for company level snipers and for squad designated marksmen. The sniper or DM is able to field a highly accurate sniper rifle that fires the same caliber ammunition as of the rest of his squad carries. A company level sniper or SDM must also be able to operate with his unit and fill a standard infantry role as a squad member. A traditional bolt-action sniper weapon is not ideal for clearing buildings and other close-in work that is common on today’s battlefields. I quickly found that the 20″ bull barreled M16, while heavier than an M4, is short and light enough that the shooter can dial the scope down to 2.5 power for CQB type work and yet quickly be ready to engage long distance targets. I found that the heavy barrel stabilized the rifle and I could fire slightly faster and more accurately than I could with the short M4 upper. Controls are familiar to anyone who has trained with the M16 family of weapons. Because the rifle looks similar to rifles carried by the other infantrymen, the sniper is not as likely to stand out as a target.
The M16 based sniper rifle is also ideal as a spotter’s weapon. The spotter then has the defensive firepower of light semi-auto, with long-range capabilities to match his training should the need arise. The rifle can also be used as a backup for the sniper’s rifle should it become disabled for any reason.
I was later issued a Barrett XM107 .50 cal. rifle and found that the match upper on the M4 lower was a perfect companion to the heavy rifle, giving the option of engaging hard or long-range targets with the .50 and soft short to medium range targets with the 5.56. This combination also allows a sniper to have a sniper rifle ready while moving into position with the Barrett in its case. Once again, the sniper has a backup option if his main weapon is disabled.
Law enforcement snipers often operate at closer ranges than military snipers. Their missions often involve more precise planning and shooting due to concerns about over-penetration and proximity of threats to civilians. While definitely falling short for tasks such as glass or barrier penetration, the better 5.56 ammunition is often ideal for close-in situations where over-penetration is an issue. The 5.56 also offers the advantage of faster followup shots, as the sight picture remains stationary and the shooter can observe hits through the scope.
It is possible to build a highly accurate rifle on the M16/AR15 platform at very little cost; a very important consideration for law enforcement agencies on a limited budget. Because of limitations of the caliber, a law enforcement team would want to field a .308 or similar caliber rifle as well.
Accuracy from the AR Platform
When I first joined the military I had very little respect for the M16. I grew up reading about soldiers and marines who battled German and Japanese soldiers with Garand rifles, routed the hun with bayonet-tipped Springfields, and charged up San Juan hill with Krag carbines. I owned each of the above rifles and an assortment of mausers and other classic rifles. Those were rifles. M16s were toys.
The performance of the worn-out old M16 I shot in basic training did nothing to impress me. The FN manufactured M16A2 I was issued several years later was far more accurate, but I still had no desire to own one. About this time I started hearing soldiers who were into long range shooting talk about AR rifles that they built for that purpose. The long range and varmint hunting crowd had discovered something that the military was slow to recognize; by an accident of design, the M16/AR15 rifle is an ideal platform upon which to build a highly accurate rifle.
In the AR rifle the barrel is threaded to the barrel extension, which functions as the receiver on a traditional rifle does. Headspace is set between the barrel and the barrel extension. The bolt locks into the barrel extension when it is in battery, and this group of parts lock together to contain the cartridge in the chamber and guide the bullet toward the target.
In any rifle, accuracy is largely the result of the perfect alignment of the bolt, barrel, and receiver, and the quality of the barrel. Interference with the barrel is generally detrimental to accuracy. Much time and expense is spent on truing and matching the mating surfaces of these parts when accurizing a bolt rifle.
In the AR rifle, the upper receiver is simply a housing for the bolt and carrier and an attachment point for the barrel. The barrel, barrel extension, and bolt are locked together. The upper receiver touches only the barrel extension where the barrel is held in place by the barrel nut. The bolt floats in the bolt carrier, which floats in the upper receiver. This allows the bolt to align itself perfectly with the face of the barrel. Attempts to tighten the fit of parts in the upper receiver have often decreased accuracy.
The beauty of this design is that free-floating a quality barrel in an AR rifle results in accuracy that rivals very expensive finely tuned bolt-action rifles.
Accurately Shooting Stock Military Rifles
Not everyone will have the luxury of a free-floating match barrel on their M16 rifle. The military is generally pretty uptight about soldiers modifying their weapons, with good reason. Law enforcement personnel are often stuck with what their agency purchased in the past or was handed down to them as surplus by the federal government. When I was deployed our designated marksmen fielded standard M16A4 rifles topped with ACOG optics.
The military has a long history of doing their best to hide the accuracy potential of the M16. The first rifles had pencil-thin barrels. The government recognized this deficiency and increased the diameter of the barrels – except for the part of the barrel under the handguard, which remained thin to save weight and so that the M203 grenade launcher could be installed. The handguards are attached by the delta ring on the barrel nut in the rear and to the barrel in the front with the thin part of the barrel between. The sling is attached to the barrel in the front. This design is the cause of the generally poor accuracy of service rifles. These rifles themselves are not necessarily inaccurate: shooters are taught to fire them an a way that hurts accuracy.
We know that the barrel is very thin under the handguards. Therefore we know that anything that puts pressure on the barrel forward of the handguards will probably affect the point of impact. Two things contact the barrel forward of the thin section at all times; the handguards and the sling. To avoid influencing the barrel, the shooter must simply avoid putting pressure on the handguards or sling.
If possible, avoid attaching a sling to the forward sling swivel at all. If the armorer can be persuaded, have the forward sling swivel removed. A single-point sling can be utilized, or a two or three-point sling that is attached to a band that is wrapped around near the delta ring. Obviously utilizing a sling for shooting is not an option. If a sling must be attached to the forward swivel, allow the sling to hang free so that it puts a minimal amount of tension on the barrel.
Do not touch the handguards. Do not allow anything else to touch the handguards. When firing without a rest, hold the rifle by the front of the magwell with the off hand. When firing from a rest, rest the rifle on the magazine, not the forearm. I was originally taught to avoid resting a rifle on a magazine, but I have since seen thousands of rounds fired from M16s and M4s rested on their magazines with few malfunctions, and none that I thought resulted from a magazine rest. (Since this article was written, FAB Defense and the Mako Group have introduced a new accessory, the MWG, to turn the magazine well into a forward vertical grip. See the article on it here)
Take a rifle with a military barrel contour, hold the receiver so that it cannot move, and pull down on the barrel with one finger. You will be shocked to see how much the barrel moves. If the barrel moves while shooting with iron sights, the front sight moves as well and will partially compensate for the variation. If optics are employed, the variation will be much more evident downrange. Some sniper instructors did a demonstration while training designated marksmen that really drove these points home. They took a good shooter and had him zero his rifle resting on the magazine. He then shot a tight group on a target at 100 meters from the magazine rest. They then placed sandbags and had the shooter rest the forearm on the sandbag. The group fired from the sandbag rest was several inches higher on the target at only 100 meters.
The obvious solution is to replace the handguards with a free-floating system. For those who have a sympathetic armorer but need to stay under the radar, several companies offer float tubes for service rifle competitors that are almost indistinguishable from issue configuration. You can see an example at the following sites: Compass Lake DCM Tube Fulton Armory DCM Tube
If replacement with a rail system is an option, there are several systems that can free-float the barrel without gunsmithing. For carbine length barrels, the VFR by the Mako Group is a great option. The rails are removable, so only necessary rails need to be installed in any of 8 locations around the handguard. There is also a model with the top rail designed for a carry-handle upper. The VFR attaches to the top rail or carry handle and also locks onto the barrel nut with no disassembly of the carbine required. The VLTOR CASV-EL also requires no disassembly of the rifle for installation. For rifles, the civilian version of the A.R.M.S. S.I.R. System can be user installed without modifying the rifle This system attaches only to the upper rail. If an armorer is willing to take a hacksaw to the delta ring and weld spring, a two-piece design such as Midwest Industries Two-Piece Free Float Rail System can be installed without removing the front sight tower and flash hider.
If a bipod is used, it should always be attached to the free-floating handguards and not to the barrel.
Adapting the M16/AR-15 for long-range shooting
There are several things that need to be taken into consideration when building a long-range AR. The first is that it is very difficult to mount a long optic far enough forward. For SDM work, some of the 1 – about 4x type optics solve this problem and fulfill that role perfectly. At 1x the optic works basically as a reflex sight. adjusting to a higher magnification allows more precision at for longer ranges or smaller targets. Companies such as Leupold, Schmit & Bender, Valdada IOR, Millett, and Burris make this type of optic. I have used the Leupold, which requires more precise eye relief and head placement than I like for this type of optic. I would not recommend it for a harder recoiling rifle, but for 5.56 it serves just fine. I have never used Schmitt & Bender’s Shot Dot, but from all I have heard it is a superior optic, with a corresponding price. Valdada’s IOR optics are very impressive. Clear, bright, and containing very well designed reticles, they are built like tanks. I used an IOR optic when deployed and preferred it to any of the others I used (mostly Leupolds). Both the 1-4x and the 1.5-8x optics are very nice and provide great flexibility to the SDM. Millett’s DMR-1, while not a Schmitt & Bender by any means, provides solid quality for the price. Optics are clear and it works well at all magnifications. There is slight distortion around the edges of the sight picture at the one power setting, but it does not interfere with function and disappears as soon as the magnification is increased. The Burris optic looks like it should work well, but I have not yet had the opportunity to test one. It seems that most of the optics with ballistic drop compensating reticles for the 5.56 are designed for the M855 or or cartridges with similar trajectories.
For dedicated long-range shooting, more traditional scopes usually work if mounted as far forward as possible in standard rings. The charging handle generally will end up under the scope in this case and an extended charging handle such as Badger Ordnance’s Tactical Latch makes operation easier. Backup iron sights will rarely fit under the scope and would require removal of the optic if they did. I would recommend a secondary sighting system such as a J-Point or Docter Optic reflex sight mounted to the scope instead.
Long optics can be moved forward if mounted in a purpose-built mount such as the LaRue Tactical SPR/M4 mount.
Mounting optics on a flat-top upper requires the use of high rings to get the necessary height, unless a riser rail of some type is used. I see no reason to use a riser for the sake of using a riser, but there are excellent risers that extend the length of the top rail. Many hanguard systems also have a top rail that attaches to the flattop rail. Some manufacturers also offer uppers with taller rails built in.
Secondly, a good stock makes a big difference. Important considerations are durability and simplicity. There are very expensive stocks out there that have buttons and wheels and really cool looks that would require three hands and an engineering degree to operate. Everyone also seems to want collapsible sniper stocks with adjustable cheekpieces. We have already established that it takes an effort to mount optics as high and as far forward as is necessary. Therefore, a shorter stock and higher cheekpiece make little sense. They also work against each other: the shorter the stock, the shorter a cheekpiece must be for the charging handle to clear. I know from experience that a collapsible buttstock on a scoped M16 never seems long enough even when wearing body armour. I like a little more length on a buttstock and a rubber pad to grip body armor when necessary. An adjustable cheekpiece is ok to adjust for different shooters.
The standard A2 buttstock, while longer than ideal for a tactical rifle, works well for a scoped rifle. My favorite stock is The Mako Group’s SSR-25 Sniper Stock. This is the buttstock used by Israeli snipers. It is simple and rugged and has an adjustable cheekpiece and a rubber buttpad. The best feature is the built-in monopod that deploys to the desired height with the touch of a button. The monopod has both fine and coarse elevation adjustment. Unlike other monopods which must be released, swung down, and then adjusted to the desired elevation, this spring-loaded monopod drops straight down to the height the rifle is held at when the release is pressed. Another stock worth mentioning is the Magpul PRS, which is well built and has an adjustable cheekpiece and length of pull. It is also fairly heavy for those who wish to add weight. Detents are captive so disassembly is easy.
There are an overwhelming variety of free-float handguards available. I prefer something with only the necessary rails for the equipment I am mounting. I used a cheap round tube in combat because I was short on cash. If I had the extra money, I would have gone with Badger Ordnance’s Stabilizer Handguard and added a rail for the PAQ-4 laser. Yankee Hill Machine and JP Enterprises both have nice, simple customizable hanguards.
As with handguards, bipod designs are becoming more numerous and expensive. Many of the newer designs are very awkward to use and have no real advantage over traditional designs. I have used and like both the Versa-Pod and the Harris bipods. My preference is the Versa-Pod. Shooters Ridge makes a copy of the Harris design as well. There are adaptors available to mount Harris or other sling swivel mount bipods to a Picatinny rail.
For the designated marksman who wants more flexibility in his weapon system, there are several forward vertical grip designs that incorporate a built in bipod of some kind. Most of these bipod grips lack any adjustment and are very unstable. Some of those that allow cant and pivot are even more unstable. The rifle will easily fall over if the shooter lets go for any reason. The exception is the Mako T-Pod and T-PodSL, and now the Gen 2 G2T-POD and G2 T-POD PR. These sturdy grips split in half to become a traditional style bipod with fully adjustable legs. The T-PodSL also features a built-in 120 lumen LED tactical light to combine three essential accessories in one compact package.
The 5.56 cartridge has had a reputation of poor to mediocre performance in combat. While I think that a 6.5mm or 7mm cartridge would be far more effective, I believe the 5.56 deserves a much better reputation than it has. Disappointment with the 5.56 is mainly due to the type of ammunition fielded.
If a 5.56 projectile passes straight through a person it makes a very small wound channel. Unlike larger calibers, for the 5.56 to kill effectively, it must fragment. If the 5.56 fragments well enough and early enough, it is quite effective. Fragmentation requires a properly designed projectile and sufficient velocity to cause fragmentation.
During the cold war, the military 62 grain M855 cartridge was developed. It was designed to be fired from a long barreled SAW at a husky potato-fed Soviet soldier wearing a flack jacket. Today our soldiers are firing that cartridge from 14.5″ barrels at 95 pound insurgents wearing man-dresses. The average target for US soldiers today is 7.3″ thick at the chest. The M855 averages 7″ of penetration before beginning to yaw or fragment. The result is small ineffective wound channels. Multiple hits are required to eliminate threats. From an M4 barrel, the velocity drops to the point that fragmentation often does not occur past 100 meters.
Fortunately, there are better options out there. I used Mk 262 mod 0, which hs now been superceded by Mk 262 mod 1. This ammunition is manufactured by Black Hills Ammunition and fires a 77 gr. open tip boat tail Sierra Match King bullet at 2783 fps from an 18″ barrel. This load is effective for hits out to 800 meters in combat conditions. A civilian version is offered by Black Hills that is safe to fire from .223 chambered rifles. It averages a little slower than the military version. Hornady manufactures a 75 gr. TAP cartridge that provides similar terminal performance. Both Mk 262 and Hornady TAP cartridges begin fragmenting at about 3″.
Black hills now has incredible 55 gr. and 62 gr. TSX cartridges that expand reliably to an average of .45 inches, and tend to maintain about 100% of their weight for deep penetration. It is an excellent intermediate barrier penetration cartridge, with excellent expansion and weight retention after penetrating vehicles or windshield glass.
These cartridges are in use by the US military and are used exclusively by many in the special operations community who have found them to be far more effective than standard M855 ammunition. They are excellent choices for both law enforcement and self defense roles.
With AR rifles now being chambered in a multitude of calibers, including highly effective 6.8 Remington SPC and 6.5 Grendel, and the SR-25/AR-10 style rifles in .308 length chamberings, the AR platform is very flexible and well suited to both military and law enforcement sniping.
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