The Knight’s Armament Company SR-15 MOD 2 14.5″ Carbine, 10,000+ Rounds Later
My Knight’s Armament Company SR-15 MOD 2 14.5″ Carbine next to Lana, my German Shepherd


In this day and age, a plethora of AR-15s hit the market, get reviewed and are well received. However, there are some rifles out there that simply do not get their fair share of coverage. One of these rifles is the Knight’s Armament Company SR-15. I have felt compelled to follow in the footsteps of John Johnston of Ballistic Radio and provide a longevity report on my SR-15 after over 10,000 rounds. It is my opinion that these are fine rifles that are often under represented and plagued by misinformation (as seen in Chris Bartocci’s YouTube video).

I want to mention that I am not endorsed or sponsored by Knight’s Armament Company. I do not do write ups or videos regularly, but I do try to do my due diligence and make them thorough.

Firstly, Knight’s Armament Company is most well known for their M110 SASS, NT4 suppressors and M4 and M5 RAS for the M4/M16 family of weapons. They aren’t a new kid on the block and have been providing products for Uncle Sam, USSOCOM and NATO allies for decades.

A Knight’s Armament Company SR-15 E3 Mod 0 Legacy pictured next to a Knight’s Armament Company SR-25 EMC. Photo courtesy of Jeremy T

SR-15 History & Overview

In regards to the SR-15/SR-16. The SR-16 is the military and law enforcement only model, which is select fire in nature. Their commercial sales model is known as the SR-15. Iterations of this model include, but are not limited to: SR-15 Match, SR-15 M4, SR-15 E3 (Mod 0 or Legacy), SR-15 Mod 1 and most recently, the SR-15 Mod 2. These rifles did not begin to really set themselves apart from the competition until the introduction of the SR-15 E3 Mod 0 or Legacy.

With the debut of the SR-15 Mod 0 Legacy model, it was one of the first production AR-15s to hit the market with ambidextrous controls on a forged receiver set. It also brought some enhancements to the rifle, particularly the E3 bolt and proprietary extended midlength gas system.

A comparison between a standard GI bolt and KAC’s E3 bolt. Note the webbed lugs and fully supported bolt face. Photo courtesy of rob_s from

The E3 bolt is unique, as it sports three major enhancements over the GI bolt design. Firstly, the lugs are both rounded and webbed, to prevent shearing of the lugs. Secondly, the cam pin hole in the bolt is smaller in diameter than GI TDP calls for to address one of the most common bolt breakages. Lastly, the extractor is lobster tailed, utilizing two extractor springs of lower K values. The extractor pivot pin is also relocated to allow for better leverage over the casing rim. The bolt face itself also fully supports the cartridge base. To date, there have not been any broken E3 bolts outside of factory testing. This tier of robustness is particularly useful for suppressed short-barreled carbines, where bolt breakages are most common.

Photo illustrates the difference between a GI bolt and a KAC E3 bolt. Note the extractor redesign, including dual extractor springs and a relocated pivot pin. Photo courtesy of Roy L of Weapon Outfitters

The proprietary extended midlength gas system (14.5″ and 16″ models only) is longer than conventional midlength gas systems, but shorter than rifle length gas systems. Like midlength gas systems, this allows chamber pressures to drop prior to the extraction process, both easing extraction and increasing bolt life. A much appreciated byproduct of an extended gas system is that it results in a much softer shooting rifle.

I find the proprietary components found in the SR-15 to be a significant upgrade and worth the price of admission.

MOD 2 Exclusive Upgrades

Exclusive to the MOD 2 iteration of the SR-15, there is both the removal of a separate barrel nut and the addition of new gas block installation methods.

With the URX4 handguard, there is no separate barrel nut. The handguard itself acts as the barrel nut. The benefits of this are great heatsinking capabilities, simplicity in installation and minimal rail flex for use with IR sighting systems mounted on the handguard.

A look into a URX4 handguard, revealing the intregrated barrel nut interface

In the search of optimization, Knight’s Armament left behind traditional gas block mounting methods. The MOD 2 gas tube is held to the gas block via a nut, trapping and minimizing gas leakage. The gas block itself is secured to the barrel shoulder via a castle nut, ensuring a good fit and proper 12 o’clock orientation every time.

A photo of KAC’s MOD 2 gas block mounting hardware. Photo courtesy of Kevin Boland, former military operations director at Knight’s Armament Company


10,000+ rounds later, I can report that reliability has been stellar. I almost exclusively shoot suppressed. I have fired American Eagle 55gr and Wolf Gold 55gr .223 Rem loads almost exclusively.

The only stoppages that I can attribute to the gun occurred during an endurance test with a suppressor. I had two failures to go into battery around the 2500 round mark when used in conjunction with a SureFire SOCOM 556-RC2 without any cleaning.

Any other stoppage was primarily due to dud primers ammunition or cracked PMAGs creating double feeds.

To date, I have not changed any springs or components in the gun.


I understand that my rifle is only a sample of one. However, I have not had the experience that nutnfancy and other YouTubers have had their rifles. 10,000+ rounds later, my rifle is still grouping roughly MOA groups with American or foreign bulk ball ammunition. I can replicate and duplicate these groups. I believe shooting match ammunition would yield sub-MOA groups.

A photo of mine illustrating the accuracy capability of the Knight’s Armament Company SR-15 MOD 2 14.5″ Carbine


The base rifle, naked with sights, is fairly light coming in at 6.4lbs. My rifle as pictured in the first photo (Aimpoint Micro, PEQ-15, QDC suppressor, Scoutlight, etc) without a magazine weighs in at 9lbs 3oz.

IR Lasers

The URX4 is ideal for the use of IR lasers. It provides a 1913 picatinny top rail and seven sides of M-LOK mounting for accessories, cable management and anything else you may need. It also exhibits minimal rail flex when loaded with weight comparatively to other handguards in its class.

Action shot of my Knight’s Armament Company SR-15 MOD 2 14.5″ Carbine

MAMS & Knight’s Armament QDC 5.56 Suppressor

The muzzle device found on the rifle is the Knight’s Armament Multi-Axis Muzzle Stability brake. I have found that it is less concussive and exhibits less flash than the SureFire SFMB556 muzzle brake, but is just as effective in taming muzzle rise.

The QDC 5.56 is Knight’s Armament’s most recent answer for a 5.56 suppressor, next of kin to the legendary NT4 corn cob suppressor. The QDC 5.56 has a unique mounting system. As the locking ring rotates, a set of ceramic ball bearings protrude from the suppressor, locking itself into the muzzle device. This allows for a very repeatable and consistent, rock solid mounting system. Point of impact shift is consistent and minimal.

Like the SureFire SOCOM 556-RC2, it too, is also low blowback. It is my unscientific observation that the QDC is louder to other observers, but quieter at the shooter’s ear than the SureFire offering.

The biggest thing that sets the QDC 5.56 apart from the SOCOM 556-RC2 is that it has yet to get stuck to the muzzle. I have had my SureFire suppressors get stuck to the muzzle on numerous occasions.

The QDC’s front end has a three prong mechanism to suppress muzzle flash.

Knight’s Armament Company QDC 5.56 suppressor and MAMS brake pictured next to a SureFire SOCOM 556-RC2 suppressor and SFMB556 brake.


Cost and Value

One of the largest gripes people have about the SR-15 is cost. I will be one of the first to argue that buying an SR-15 is actually a bargain for a quality rifle.

In regards to cost, the SR-15 is most commonly compared to BCM and Daniel Defense offerings with free-floated handguards. Most of these are priced in the 1200 to 1550 dollar range. However, almost all of them come without sights, ambidextrous controls, or an upgraded bolt carrier group and gas system. When you add these items or their equivalents, cost likely exceeds the street price of an SR-15.

With a SR-15, you will receive a set of KAC’s flagship micro sights, their two stage trigger (similar to the Geissele SSA), ambidextrous controls on a forged receiver set along with the E3 bolt carrier group and extended KAC midlength gas system. Street price online for 16″ SR-15s is typically anywhere between 2150 to 2300 dollars (as of this writing, February 2018). Prices on the 14.5″ NFA models are a little higher and require the cost of a tax stamp or a compliant muzzle device being pinned to achieve a 16.1″ barrel length and removal from the NFA registry.


With 10,000+ rounds fired to date, I have yet to see anything out of the ordinary. All of the components are wearing well over time. I do intend to shoot out the barrel in this gun and provide another longevity report in the future.

Next time you are looking for a home defense or professional duty rifle, I highly suggest you take a close look at the Knight’s Armament SR-15.

My SR-15 MOD 2 14.5″ Carbine and my EDC for the longest time


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