The mounted Centurion Arms CMR Rail. Note the removable rail segments on the front right side and bottom. Also on the rail are the Centurion arms grip panels. On the top front of the rail is the A.R.M.S. #41l-F folding front sight.
By Christopher R. Bartocci
The AR-10 has achieved near epic popularity over the last 20 years. Ironically, in the late 1950s, the Ordnance Corps of the U.S. Army felt it was not good enough to replace the M14. Although the AR-10 was light years ahead of the M14 in materials, weight and reliability, it was far more of a priority to keep Springfield and Rock Island Armory’s producing the M14 rifles. Politics, careers and personal interests heavily outweighed what was best for the U.S. military. They would soon be called upon not only to answer for that mistake but would lose the M14 in favor of the new AR-15. Much heavier consequence to follow would close down both armories for good and put weapons development and production in commercial hands. The Ordnance Corps was abolished by Secretary of Defense Robert S. McNamara.
Due to the perseverance of Gene Stoner, the AR-10 was brought back to life in the early 1990s when he went to work with C. Reed Knight, Jr., president of Knight’s Armament Company. The introduction of the SR-25 resurrected the AR-10 from the scrap heap of the Ordnance Corps lack of vision and foresight. Since 1994, there are several companies that have come out with their own versions of the AR-10-type rifles; the leading companies being Knight’s, ArmaLite (at the time owned by Mark Westrom) and DPMS. There would be two patterns of receivers, the KAC/ArmaLite pattern and DPMS pattern. What separated these two patterns was the shape of the rear portion of the upper receiver and it’s mating surface on the lower receiver. The SR-25/ArmaLite maintained the same more squared profile of the original AR-10 compared to the rounded profile of the DPMS. Neither was better than the other; perhaps it was just the DPMS way of securing their own brand and keeping out interchangeability between the earlier rifles.
Since then, numerous companies have come on line with their own AR-10-type variants including Rock River Arms, JP Rifles, Colt, LMT, Larue, Bushmaster, Heckler & Koch, SIG, and Remington to name a VERY few. Many of these companies don’t actually manufacture their own components. All of them purchase their receiver forgings from the same forging companies such as Cerro Forge, Anchor Harvey, Aluminum Brass Forge, Cardinal Forge and so on. For those companies who do not have the ability or do not wish to invest in the machinery necessary to manufacture the lower receiver, they subcontract out the manufacturing and finishing of their receivers. One of those companies that has performed this service to several name brand Black Rifle companies is Aero Precision. This author first heard of Aero Precision while researching the ArmaLite SPR monolithic receiver. The top rail was monolithic manufactured from a single forging but the other three sides of the handguard/rail were assembled by removable rail sections. The president of ArmaLite, then Mark Westrom, said that their SPR/COP was a joint effort with a company called Aero Precision. After some research it was determined that Aero Precision manufactured the upper and lower receivers for both the M15 and AR-10 series rifles for ArmaLite.
Aero Precision opened their doors in 1995. Their shop was in the garage of the president of the company, Scott Dover. Around the 1998 time period, the company entered the small arms business doing upper and lower receivers for a wide variety of OEM companies. Aero Precision flourished and grew exponentially and were very busy making receivers for several of the OEM’s during the major rush in black rifle sales. However, they thought if they were making all these receivers for these other companies, why not make and sell them themselves? This was a major opportunity not only to make money but to get the company name out there. Most consumers who bought rifles made of their receivers had never heard of Aero Precision. In 2008 that changed and Aero Precision entered the market themselves. They started with standard upper and lower 5.56mm receivers and flourished with selling their military grade high quality receivers at very competitive prices. At this same point in time the industry began to see a shift in people getting away from buying a complete rifle in favor of building their own custom rifle from the vast pool of extremely high quality component manufacturers.
In 2013, Aero Precision introduced their second generation ambidextrous lower receiver that used the Teal Blue Bravo PDQ bolt catch lever. There is a channel machined into the top of the lower receiver extending the bolt release to the right side and a lever protruded from the right side enabling the trigger finger of a left handed shooter to engage and disengage to bolt. The lower receiver was supplied with a Battle Arms Development Ambidextrous Safety Selector (BAD ASS) and a Norgon ambidextrous magazine release that provides a lever right on the left side of the mag catch, which works easily and smoothly. This product is standard on all Canadian C7A2 rifles and is part of the U.S. M4 Product Improvement that is in part making the rifles ambidextrous.
Aero Precision has offered the standard flat top Mil-Std 1913 upper receiver since the beginning. They added to their lineup both carbine (with extended feed ramps) as well as standard rifle receivers (without feed ramps). They also added an upper receiver minus the forward assist assembly. This was a great deletion due to the fact the forward assist should never have been added to the rifle in the first place. Gene Stoner himself fought the Army on this saying it would create more problems than it would ever solve. You should never force a round into the chamber. If the bolt does not close and lock, the rifle is telling you something isn’t right – get that round out, don’t slam it in.
Aero Precision would continue to diversify with the addition of both 1 inch and 30mm very lightweight scope mounts. They also offer a mount for an Aimpoint optic. The SPR/COP upper receiver is sold by Aero Precision as well as ArmaLite. Rumor has it that Aero Precision is working on an AR-10-type SPR upper though no release day has been set. Aero Precision also offers Cerakote receivers in various colors.
Early on, Aero Precision offered some of their own AR-10-type lower receivers that took the ArmaLite converted M14 magazine. However, it was not until 2014 that Aero Precision would enter the AR-10 market with their new M5 receivers. They offer both a standard upper receiver that includes the ejection port cover, fired cartridge case deflector as well as the forward assist manufactured from 7075 T6 aircraft grade aluminum. The sample receiver provided is very well manufactured and clearly significant attention to fit and finish was paid. The receiver has the DPMS contour on the rear of the upper. The forward assist assembly is held in by a set screw rather than a roll pin and the rails are numbered on the top of the receiver.
The lower receiver is also manufactured from a 7075 T6 aircraft grade aluminum forging. The magwell has an aggressive bevel to make magazine loading in low to no light easy. The receiver will accept either a 90° or 60° selector lever, with the marking on both sides of the receiver. There is a pictogram with a projectile for fire and a projectile with an X though it to indicate safe. There is a magazine well boss to protect the magazine release button from accidental release. The fit to the upper and lower receiver is superb. The bolt catch is held in by a set screw rather than a roll pin, which makes assembly much easier and no chance of dinging up the finish on the receiver. The lower accepts the standard SR-25/AR-10-type magazine. This lower receiver has been tested with Magpul PMag, Lancer L7, KAC, CProducts Defense and ASC magazines. All inserted freely and dropped free.
Also provided for T&E is a newly produced Aero Precision barrel. This midlength gas system barrel is stainless steel and button cut from a barrel blank made of 416 stainless steel. They also offer barrels manufactured from 4150 CMV. The barrels are rifled with a 1 turn in 10 inch twist. This particular barrel is 16 inches in length; Aero Precision offers 7.62x51mm/.308 Win. caliber barrels in 10.5, 14.5, 16, 18 and 20 inch lengths. The barrels are not made directly by Aero Precision but by their sister company Ballistic Advantage. Aero Precision acquired Ballistic Advantage in December of 2014.
The receivers arrived stripped and the barrel only was equipped with the barrel extension. In order to test the rife it needed to be built up into a complete rifle. Starting with the lower, an LMT dedicated 7.62mm receiver extension was used along with the SOPMOD buttstock. The receiver extension is hard coat anodized and then covered with dry-film lubricant – this helps to prevent rattling of the stock. There are six positions for the stock allowing for adjustment from bare chest to heavy body armor. The LMT H3 buffer and spring were used as well. The selector chosen was the Battle Arms Development Ambidextrous Safety Selector (BAD ASS) with the 60° degree throw. This is one of the most comfortable of the lot; it is wide enough to operate with heavy gloves. The trigger chosen was the standard Mil-Spec trigger group – nothing fancy, just old reliable – breaking at 6.25 pounds. The bolt catch is a standard DPMS-type. The magazine release button is manufactured by Seekins Precision and is made from a billet. It is very comfortable and the dimple pattern on the surface of the button prevents your finger from slipping. The front pivot pin and rear takedown pin are manufactured by DPMS.
The upper receiver was equipped with a standard Mil-Spec forward assist assembly and a DPMS 7.62mm ejection port cover door. The fired cartridge case deflector is perhaps the largest I have seen. The charging handle selected was the AXTS Raptor, an ambidextrous charging handle that is easily grabbed from the side. They protrude long enough that they are easily accessible with a large optic.
The bolt carrier group chosen for this rifle is a new production ArmaLite bolt carrier group. This model has forward assist serrations and is very well made. The carrier key is properly staked. There is a rubber O-ring around the extractor, which has two embedded extractor springs. There was a search for this type of bolt carrier that was chrome plated, but the only two chrome plated 7.62 cal. bolt carriers found did not have forward assist notches.
As previously stated, the 16 inch stainless steel barrel came only with the barrel extension installed. This is for good reason as customers all like different types of gas blocks/front sight assemblies. Some may want a low profile gas block so it will be hidden/protected under the handguard. Some may want a gas block with an adjustable gas system. Some may want to use a suppressor and have a gas block with a 2-position valve and others may want a full front sight. Then there are some like this author who want a drilled and pinned gas block instead of it being secured with set screws. Obviously, there is no one configuration that will keep everyone happy, so it is best to let the individual decide what configuration they want. Decided for this rifle was the Centurion Arms CMR (Centurion Modular Rail) 14 inch rail system. Centurion Arms is owned and operated by Monty LeClair. Monty, a currently active duty Navy SEAL, brings real world experience to his designs along with modern manufacturing to come out with a product he would carry on his own weapon if deployed. The CMR rail uses a proprietary barrel nut that does not require indexing of the gas tube. This offers two major benefits. First, it makes installation a whole lot easier. Secondly, it permits the application of proper torque without exceeding the Mil Specs. Ideally, the barrel nut should have a final torque of around 60 ft lbs. When tightening a normal barrel nut you torque to 35 ft lbs 3 times and then adjust to align the gas tube. That indexing torque can drive the barrel nut past the 80 ft lbs maximum. With the Centurion CMR barrel nut, you will torque the barrel nut to 30 back off and then to 45 and back off and finally to 60 ft lbs. The reason for torqueing three times is to ensure you do not get a false torque reading due to a bur on the threads of the upper or the barrel nut which can cause the barrel to come loose during firing. The handguard is manufactured from 6061 T6 aircraft grade aluminum and this particular handguard is 14 inches in length. The 12 o’clock rail is continuous from the upper receiver to the end. The 3, 6 and 9 o’clock positions contain threaded holes for removable rail panels or handguard grip panels. The weight of the handguard is 15.9 ounces with the barrel nut. The inside diameter is 1.25 inches making it comfortable and not overly cumbersome. The overall height is 2.17 inches and width 1.73 inches. There are four quick detachment points on the front and rear side rails. Rail panels come in different sizes so the operator can only use what they need. The rail is held in place by three locking screws. The kit does come with a proprietary barrel nut wrench.
The upper receiver and barrel were sent to Monty LeClair of Centurion Arms to assemble – particularly due to the desire to have the gas block pinned in place, which he was able to do. He then assembled the barrel and rail to the upper receiver. The muzzle was fitted with an Advanced Armament flash suppressor/sound suppressor mount.
For back-up iron sights the A.R.M.S., Inc. #40L-P rear sight and the #40L-4 were used. The #40L-4 was designed for U.S. Special Operations Forces under contract with Crane Naval Surface Warfare Center. The P stands for precision. The sight is adjustable for windage only with a knob on the left side of the sight. There are two apertures. Immediately when the sight is engaged the user sees the standard long range aperture. Pulling rearward on that aperture makes it fold back 90° exposing the larger short range aperture. The #40L-F is a folding front sight that when engaged uses the standard M16 4-position square front sight post. All elevation adjustments are done with the front sight post. These are very durable metal back up sights.
The scope chosen is the Night Force BEAST. BEAST is an acronym for Best Example of Advanced Scope Technology. The BEAST is a 5-25 x 56 F1 with a tube diameter of 34mm/1.34 inches. The objective outer diameter is 65mm with an exit pupil diameter of 5x: 8.3mm and 25x at 2.3mm. The eyepiece outer diameter is 46mm. The field of view at 100 yards is 5x at18.7 feet and 25x at 4.92 fee Eye relief is 3.35 to 3.54 inches. The internal adjustment range for elevation is 120 MOA and windage 80 MOA. Each click is .50 and .250 MOA. The parallax adjustment is 45 yd-∞. The optics are crystal clear. This would be a standard of excellence in long range rifle optics.
The rifle was tested with various magazines that included the new Magpul Gen 3 magazines with 20- and 25-round capacity. The rifle was also tested with the newly released Lancer L7 20-round magazine and the ASC, CProducts Defense and KAC steel 20-round magazines.
The rifle was tested with different types of ammunition. There were 100 rounds of Federal XM80 7.62x51mm NATO ball, 40 rounds of Black Hills Ammunition 7.62x51mm 175gr OTM and Federal .308 Win. 168gr BTHP Gold Medal. There were no malfunctions of any sort and the rifle functioned flawlessly. The best group at 100 yards was with the Black Hills 7.62x51mm 175gr OTM (equivalent to and considered by many to be better than the M118LR) with a 1.5 inch group. Unfortunately, weather was a factor. The brisk 15° weather and -5 wind-chill factor played a part. I do expect under better conditions the group size would have improved. The barrel was also not broken in, it was brand new.
With the AR market still at all time records, the consumers are becoming vastly more educated. With the sheer number of options of components and variations of those components consumers are able to customize their rifle to suit their own needs. Aero Precision provides excellent Mil-Spec quality receivers at competitive prices that may start out as the basic building block of a custom 7.62mm or 5.56mm rifle. They also offer excellent quality barrel at competitive prices. For those who want to purchase an already assembled rifle, Aero Precision offers complete rifles in various configurations as well. Every year they add several new components and complete weapons to their catalog.
|This article first appeared in Small Arms Review V20N3 (April 2016)|
and was posted online on February 19, 2016