The SR-25 designation itself is a contraction, Stoner Rifle-25, formed by adding the 10 of AR-10 to the 15 of AR-15¹. Before any military customer adopted it, KAC sold more than 3,000 SR-25 rifles commercially, building a reputation for accuracy that later drove US Special Operations Command toward the design^1,2. The United States Navy SEALs adopted a shortened version as the Mk 11 Mod 0 in May 2000, and the platform subsequently spread to Israel, Australia, the Philippines, and several other forces³. Despite its age, the SR-25 remains directly relevant to any search for how a 7.62x51mm NATO designated marksman rifle works, what it costs on the commercial market, and how it compares to its own institutional descendant, the M110 family.

Because the SR-25 predates its own military derivatives, confusion between it and the Army's later M110 Semi-Automatic Sniper System is common. The SR-25 is the ancestor platform, the rifle Stoner and Knight built first, while the M110, the M110A1, and the M110A2 are distinct, separately adopted rifles that grew out of it years later. The SR-25's own history below covers the rifle and its direct SOF-era derivative, the Mk 11 Mod 0, without absorbing the M110 family's separate service history.

The Direct-Impingement Action Borrowed From the AR-15

The SR-25's action is gas-operated, using AR-15-style direct gas impingement rather than a piston, driving a rotating bolt with seven locking lugs¹. It fires from a closed bolt, semi-automatic only, and unlike the AR-15/M16 it has no forward assist button, though it keeps the brass deflector behind the ejection port¹. The upper and lower receivers follow the AR-10 pattern, scaled and reinforced for 7.62mm NATO pressures, machined from aircraft-grade aluminum with a flat-top Picatinny rail¹. Controls are fully ambidextrous, and the detachable magazine feeds from 10- or 20-round steel box magazines¹.

Barrel length is where the SR-25 name covers real variation rather than one fixed rifle. The original SR-25 Match Rifle carried a heavy, free-floating 24-inch (610mm) barrel with a 1:11.25-inch twist, made originally by Remington Arms using 5R rifling¹. The SR-25 Enhanced Match Carbine cut that down to 16 inches (406-410mm) for roughly 7.5 lb (3.4 kg) unscoped, while the military Mk 11 Mod 0 configuration split the difference at 20 inches (508-510mm)⁵. A fully equipped Mk 11 Mod 0, rifle, suppressor, optic, and bipod together, weighs about 15.3 lb (6.9 kg), considerably heavier than the bare Match Rifle's 10.75 lb (4.88 kg)⁵. The barrel attaches independently of the handguard on every version, a free-floating arrangement that is a large part of why the SR-25 reaches sub-MOA, often cited around 0.5 MOA, accuracy with match ammunition^1,5.

The trigger is an adjustable two-stage match unit, and the accuracy that trigger and barrel combination delivers comes with a real cost. Some special operations units, 1st Special Forces Group among them, reportedly preferred bolt-action rifles in the field because the SR-25's semi-automatic action demands tighter maintenance than a bolt gun under harsh conditions⁵. Chris Kyle, describing his own combat experience with the rifle, put it plainly, there were other issues with the weapon, however, and personally it was never one of my favorites⁶. That is a genuine, sourced disagreement about the SR-25's field reliability, not a universal verdict, since the same rifle has stayed in continuous SOF and law-enforcement use for over two decades.

Chambering, Ballistics, and Effective Range

The SR-25 is chambered for 7.62x51mm NATO, commercially compatible with .308 Winchester, and it was designed around 168-grain open-tip match (OTM) ammunition, with military M118 and M118LR loads used in service¹. Muzzle velocity runs around 2,571 ft/s (784 m/s) with 7.62mm NATO ball ammunition⁵. Effective range depends heavily on configuration. Carbine-length builds are generally cited around 600-800 meters, while the 20-inch precision configuration has been credited past 1,000 meters in favorable conditions, with a general consensus effective range near 600-800 meters across carbine and combat use⁵. Both the SR-25's caliber and its effective range are directly comparable to the smaller Mk 12 Special Purpose Rifle, a 5.56x45mm design built to fill the gap between the M4 carbine and the heavier SR-25 rather than replace it.

Eugene Stoner's AR-10 and the Rifle It Lost To

The SR-25's design begins with the AR-10, Eugene Stoner's 7.62x51mm NATO battle rifle designed at ArmaLite in the late 1950s. The AR-10 lost the US Army's rifle trials to the M14, and ArmaLite's own commercial fortunes with the design never matched its later influence¹. Stoner's team scaled the same basic layout down for the 5.56mm AR-15, which became the M16, and it was that success, not the AR-10's own military career, that gave the platform its lasting reputation. Decades later, Stoner returned to the larger-caliber AR-10 architecture, this time aiming squarely at a precision role rather than general infantry issue.

Knight's Armament Company and the Stoner-Knight Collaboration

C. Reed Knight Jr. founded Knight's Armament Company in Vero Beach, Florida, in the late 1970s to serve the specialized equipment needs of special operations and counter-terrorism units⁷. Stoner and Knight worked together through the late 1980s and into the early 1990s on what became the SR-25, and KAC moved into a 460-acre former Tomahawk-missile production campus in Titusville, Florida, in 2002 as demand grew during the War on Terror⁷. That Titusville facility now houses Knight's own tribute collection to Stoner alongside one of the largest privately held firearms and armored vehicle collections in the country⁷.

From a Commercial Rifle to the Mk 11 Mod 0

The US Navy evaluated the SR-25 for roughly five years before Naval Special Warfare Command adopted a shortened, 20-inch-barrel version in May 2000 as the Mk 11 Mod 0, under a sole-source contract for an initial 300 units³. The full Mk 11 Mod 0 weapon system paired the rifle with a Leupold scope, folding backup iron sights, a Harris bipod, and a quick-detachable KAC suppressor, aimed specifically at urban-combat sniping where a semi-automatic action's faster repeat engagement mattered more than a bolt gun's simplicity³. That adoption made the SR-25, in its Mk 11 form, one of the earliest purpose-built semi-automatic precision platforms fielded by US special operations forces at scale, and it is widely credited with helping popularize the modern designated marksman rifle concept within Western militaries^1,3.

The US Army's own adoption came later and under a different name. The 2005 XM110 Semi-Automatic Sniper System competition, won by a KAC-modified SR-25/Mk 11 design designated SR-XM110, produced the M110 Semi-Automatic Sniper System, fielded from 2008 with an adjustable stock, modified rail, flash hider, and unified scope mount distinguishing it from the SR-25 it grew out of⁸. USMC snipers adopted a related M110-upper configuration around 2010, and by mid-2011 SOCOM began divesting its own Mk 11 Mod 0 rifles in favor of the FN SCAR-based SSR Mk 20, a transition complete by 2017^3,4.

The SR-25's tan-painted profile is also recognizable well outside military and law-enforcement circles, appearing repeatedly in film, television, and video games over the past two decades.

Tora Bora and Operation Anaconda, Afghanistan 2001-2002

Delta Force snipers carried SR-25/Mk 11-family rifles during the Battle of Tora Bora in December 2001, hunting al-Qaeda leadership in the cave complexes of the Safed Koh mountains during the war in Afghanistan⁹. Roughly 70 Delta Force operators worked from a forward base near the caves, using GPS devices and intercepted communications to call in precision airstrikes rather than mount large infantry assaults⁹. During Operation Anaconda in the Shah-i-Kot Valley in March 2002, Navy SEAL Senior Chief Britt Slabinski reportedly carried an Mk 11 Mod 0, though this specific detail is less firmly documented than the Tora Bora deployment and should be treated with some caution.

Urban Combat in the Iraq War

Army sniper teams and Marine Corps designated marksmen carried the Mk 11 into the Iraq War's urban fighting, notably around Fallujah and Ramadi, where the rifle's semi-automatic action suited the fast, close-range engagements typical of house-to-house combat better than a bolt-action sniper rifle would.

The Maersk Alabama Rescue Off Somalia, 2009

The SR-25's single most publicized combat use came far from any conventional battlefield. During the Maersk Alabama hijacking in April 2009, Somali pirates held Captain Richard Phillips hostage in a lifeboat in the Gulf of Aden after a failed attempt to hijack the container ship¹⁰. On April 12, 2009, three DEVGRU snipers aboard the USS Bainbridge fired simultaneously at night using suppressed Mk 11 Mod 0 (SR-25) rifles fitted with night-vision optics, killing all three pirates holding Phillips and ending the standoff¹⁰. It remains one of the best-documented, highest-profile confirmed uses of the SR-25 anywhere in its service history¹⁰.

Zamboanga and Marawi, Philippine Urban Sieges

In the Philippines, the PNP Special Action Force used SR-25 rifles during the Zamboanga City crisis in September 2013, when a rogue MNLF faction attempted to raise a separatist flag over the city, a nearly three-week siege in which three SAF operators were killed¹¹. Four years later, during the Siege of Marawi from May to October 2017, the Philippine Army's Light Reaction Regiment fielded a dedicated Light Reaction Sniper Task Group armed with SR-25-pattern rifles against pro-ISIS insurgents entrenched in the city, again losing operators in the fighting^12,13. Both sieges sit within the broader, decades-long Moro conflict in the southern Philippines, and both demonstrate the same urban, close-quarters role the SR-25 filled in Iraq.

The SR-25 Match Rifle, the original early-1990s configuration, carried a 24-inch heavy free-float barrel, a fiberglass handguard, and the two-stage match trigger described above. KAC later introduced the SR-25 Enhanced Match Rifle and Enhanced Match Carbine, offering 20-inch and 16-inch barrel options on a URX II modular rail, and the SR-25 Lightweight Match Rifle, a 20-inch-barrel build using KAC's first-generation free-float rail, which the US Navy adopted as the Mk 11 Mod 0 in 2000^1,3. The Marine Corps' Mk 11 Mod 1 substituted an M110-style upper receiver and URX modular rail as a transitional step, and the Mk 11 Mod 2 designation was USSOCOM's equivalent name for the complete M110 rifle⁸.

KAC continues to sell an SR-25 Precision Rifle (PR) commercially, a modern 20-inch-barrel build with an M-LOK handguard, alongside compact K-series models, the K5 (14.5in, 7.62 NATO), K7 (14.5in, 6.5 Creedmoor), K3 (16in, 7.62 NATO), K6 (16in, 6.5 Creedmoor), A2 (20in, 7.62 NATO), and A3 (22in, 6.5 Creedmoor)¹⁴. That current commercial catalog, sold and documented directly on Knight's Armament Company's own site, is the clearest evidence that the SR-25 line itself never went out of production even after its military SOCOM contracts ended¹⁴.

An SR-25 ECR (Enhanced Combat Rifle) is a genuine, documented modern KAC commercial and law-enforcement product. One further designation sometimes cited online, an EKIA variant, could not be verified as a real Knight's Armament product or designation across the company's own materials, reference databases, or dealer listings, and it is omitted here rather than described from unverified sources.

The SR-25's most consequential institutional descendant is really a separate weapon family rather than a single variant. The Army's M110, later the M110A1, the compact M110A1, the M110A1 Squad Designated Marksman Rifle, and the M110A2, all descend from the SR-25/Mk 11 program and share its basic action and 7.62mm chambering, while carrying their own separate adoption dates, service histories, and specifications that belong to their own articles rather than this one.

The United States remains the SR-25's largest user, through Navy SEAL Mk 11 Mod 0 rifles (now largely retired from front-line SOCOM service) and continued law-enforcement and commercial ownership. Israel operates the SR-25 within its special forces community. Australia fields it across the Australian Army, the RAAF Airfield Defence Guards, and state Police Tactical Groups. The Philippines is one of the SR-25's most combat-experienced operators, through the PNP Special Action Force and the Army's Light Reaction Regiment, both of which used the rifle in the Zamboanga and Marawi sieges described above.

Beyond those four, the SR-25 is also in service with Greece's Hellenic Navy SEALs, Italy's Army, Navy, and Carabinieri, the Malaysian Army, Poland's GROM special forces unit, and the Thai Royal Army¹⁵. That spread across nine confirmed operators, well beyond the four countries commonly listed for it, reflects how widely a rifle first sold as a civilian precision product before any military interest at all eventually traveled once SOF units in multiple countries adopted it independently of each other.

Knight's Armament built the M110 family directly out of the SR-25/Mk 11 program, so separating the two is a matter of institutional timeline and added features rather than a mechanical redesign. Both use the same AR-10-derived, direct-impingement, 7.62x51mm NATO action. The M110A1 adds a folding, adjustable stock and a fully modular rail system the original SR-25 Match Rifle never had, reflecting a decade of additional Army requirements layered onto the same basic rifle. A buyer or force choosing between the two today is really choosing between an older, simpler, still-in-production commercial platform and a newer, more accessorized military-specific rifle built from it.

A sharper mechanical contrast comes from the German Heckler & Koch G28, also chambered in 7.62x51mm NATO but running a short-stroke gas piston rather than direct impingement. That single difference drives most of the practical gap between the two rifles, since a piston system runs cooler and typically tolerates harsher field conditions with less cleaning, exactly the reliability trade-off some SR-25 users reported in the field^5,6. Both rifles hit similar sub-MOA accuracy figures on paper, and the difference between them shows up in maintenance schedules more than in a target's group size.

For a lighter, faster-handling alternative in the same US inventory, the Mk 12 Special Purpose Rifle trades the SR-25's 7.62mm punch and longer range for a 5.56x45mm chambering and reduced weight, a role difference (squad-level marksman rifle versus longer-range designated marksman rifle) rather than a simple better-or-worse comparison.

What caliber is the SR-25 rifle The SR-25 is chambered in 7.62x51mm NATO, commercially compatible with .308 Winchester ammunition¹.

Is the SR-25 still in service The US military's Mk 11 Mod 0 SOCOM contracts ended between 2011 and 2017, replaced mostly by the FN SCAR-based SSR Mk 20⁴. The SR-25 itself remains in active service with forces including Israel, Australia, the Philippines, Greece, Italy, Malaysia, Poland, and Thailand, and Knight's Armament still manufactures and sells the rifle commercially today^14,15.

What is the difference between the SR-25 and the M110 The SR-25 is the original Knight's Armament design from 1990. The M110 family is a separate, later US Army-adopted rifle built from the SR-25/Mk 11 program starting with the 2005 XM110 competition, adding an adjustable stock and modular rail the SR-25 itself never had⁸.

How much does an SR-25 rifle cost No official military unit-procurement cost for the Mk 11 Mod 0 contract has ever been published. Complete commercial SR-25-family rifles retail for roughly $4,600 to $5,040 through specialty dealers¹⁴.

What is the effective range of the SR-25 Carbine-length configurations are generally cited around 600-800 meters, while 20-inch precision builds have been credited past 1,000 meters in favorable conditions⁵.