Skip to main content

The Combat Proven MK 12: A Remarkable Victory

Precision Reflex's Mk 12 SPR Mod 0: One of the most successful military AR variants ever!

The Combat Proven MK 12: A Remarkable Victory
The Mk 12 SPR (Special Purpose Rifle) was voted one of the top three weapons systems fielded in Afghanistan, and for good reason. This DMR-type rifle proved its worth in combat. Here Tarr tests out a Mk 12 Mod 0 using Black Hills’ Mk 262 Mod 1 ammunition, which was designed specifically for this weapons system. (Photo Provided by Author)

Affiliate Disclosure: This page contains affiliate links. We earn from qualifying purchases.

One of the most successful military AR variants ever was the Mk 12 SPR (Special Purpose Rifle). This designated marksman’s rifle was in military service from 2002–2017 and was voted one of the top three weapons systems fielded in Afghanistan (the others being the Mk 19 full-auto grenade launcher and the M240 machine gun). It sprang to life right at the start of the war on terror, and sports an excellent combination of commercially available components which appeared during the early days of the AR boom, specced by people who knew what they were doing.

When it comes to small arms, as a general rule, innovation doesn’t come from government or the military, it comes from private industry. As David Fortier wrote almost fifteen years ago, “The Mk 12 family, along with its ammunition, is perhaps the best example of technology developed by competitive shooters being put to use by the military.”

Two SPR Uppers displayed on bench top
Early SPR upper receiver assemblies on hand at PRI and used for reference. The camouflaged upper was sent back from Afghanistan in 2008 or so as after about 10,000 rounds the barrel was shot out. (Photo Provided by Author)

There were three distinct Mk 12 variants—the Mod 0, Mod 1, and Mod H. SPRs were built for all U.S. Special Forces, and were fielded by Navy SEALs, the U.S. Army’s 5th Special Forces Group, Army Rangers, and others. Whether you’re interested in “clone” military rifles, or simply accurate ARs, the Mk 12 SPR is a fascinating piece of history. And they’re still available—for this article I secured a Mk 12 SPR Mod 0 in FDE and Mk 12 SPR Mod H in black from Precision Reflex, Inc. PRI has been involved with the SPR project from the beginning, and many of their parts were specifically requested for the initial builds.


Around 2000, the SPR program grew out of the SOPMOD program and the “Recce” rifles (pronounced “recky” and short for reconnaissance) being fielded by some Navy SEALs and other SF troopers. SOPMOD stands for Special Operations Peculiar Modification kit, and is an accessory system for M4s, etc., that offers improved optics, grips, handguards, etc. The SEAL Recce rifles were ARs with longer and/or heavier barrels than the M4, often free floating inside commercially available handguards, topped by magnified optics. SEALs, and other SF troops, began fielding accurized ARs in the 1990s.

The Mk 12 SPR grew out of a desire for a rifle more accurate and with longer range than the M4, but shorter/lighter than the SR-25, which was an accurized .308 AR-10 variant produced by Knight’s Armament Company. SPR originally stood for Special Purpose Receiver, and the idea was soldiers could field an accurized, improved complete SPR top end they could put on their M4 lower receiver when bad guys popped their heads up at distance. This isn’t what happened; the SF troopers in the mountains of Afghanistan much preferred their SPR uppers, and soon were leaving their M4 uppers back in the barracks.

The Special Purpose Receiver was a hit, but standard M4 triggers were not a good match for a precision upper. Soon SPR became the Special Purpose Rifle and type-classified as the Mk 12 as complete guns were sent into the field. The SPR program was run by NSWC (Naval Surface Warfare Center Crane Division, in Indiana), with the intent to develop an AR-15-based designated marksman rifle for use by all U.S. Special Forces. Unlike the SEAL Recce rifle, which was more of a concept, the people behind the SPR program (which included Navy and Army personnel) came up with a number of rigid specifications for this new rifle.

First, the Mk 12 SPR would sport a heavy, 18-inch barrel. Officially, the 18-inch barrel of the original SPR was a stainless steel Douglas tube, but according to Tony Holdren at PRI, the men at NSWC used whatever match stainless steel barrels they could get when building the original SPRs, and that included tubes from Douglas, Schneider, Krieger, and Knight’s Armament. These barrels had a rifle-length gas system 
and a 1:7-inch twist rate.

Muzzle brake and threaded cap for suppressor attachement
The Ops Inc muzzle brake has a removable collar which protects the threads meant for the 12th model Ops Inc suppressor, which mates to the tapered collar forward of the front sight. (Photo Provided by Author)

The barrel muzzles were threaded the standard 1/2x28 and tipped with a muzzle device not often seen these days, a muzzle brake suppressor mount made by Ops Inc. (which still exists as AE, Allen Enterprises). This single chamber muzzle brake has a threaded exterior (with a thread protector) designed to work with their suppressor. Two inches behind the muzzle brake you’ll see a tapered collar on the barrel that is meant to stabilize the Ops Inc. Suppressor.

Before I dive too deep into the weeds, let me point this out—the Mk 12 SPR was such a huge success not because of the rifle, but because it was a complete system, including rifle, suppressor, magnified optic, and improved ammunition—the Mk 262 Mod 1 cartridge, which I will cover in a bit. Mk 12 Mod 0 SPRs are distinctive in part because of their handguard. While handguards which free float the barrel of an AR-15 have been around since at least the 1980s, almost all of them circa 2000 were meant for competition, and either too heavy or not strong enough for military use.

PRI’s round carbon fiber forearm was the exception to this, some would say the perfect balance between strength and weight, and soon became very popular with 3-Gun shooters. My first competition AR from TTI sported this same handguard. But it wasn’t just the gamesmen who liked this handguard but some serious folks as well, which is why it was specced for the original SPR. It added weight when compared to a GI polymer handguard, but it was far stronger. The round carbon fiber forearm is attached to the barrel nut and then secured/covered with an aluminum collar, which is what you see. The carbon fiber forearm is 1.75-inch in diameter.

Recommended


Carbon fiber rifle barrels are all the rage these days, for two reasons: their light weight, and their resistance to heat. The PRI handguards are somewhat thick, and between the thickness and the heat resistance of the carbon fiber material it is almost impossible to get the handguard too hot to hold—another bonus for a military rifle meant for use in hot climates. They are also strong, with very little flex even without an ARMS monolithic rail bolted to the top. It is possible to attach rail sections to the handguard at 3, 6, and 9 o’clock. While you can buy a handguard from PRI with a natural carbon fiber finish, the ones supplied for the Mk 12s all had either black or FDE Cerakote finishes. PRI was Cerakoting their parts before anyone else had even heard of Cerakote.

Coyote tan colored Rail and Flip-up front sight gas block
The original #38 Swan Sleeve has sections meant for different purposes, including the forward portion meant specifically for a PEQ IR laser. (Photo Provided by Author)

The original SPR wore a #38 Swan Sleeve from ARMS. This MIL STD 1913 rail attached to both the upper receiver and the handguard, providing one continuous monolithic rail surface, long enough not just for a daylight optic but for night vision optic in front of that, as well as a spot at the front for a PEQ (IR laser). It had a flip-up rear sight which worked with the PRI front sight. It adds 0.45 of an inch in height to the receiver.

Let’s talk about that flip-up sight. The first-generation front sights had an elevation drum that was removed in later models. It sits atop a gas block just in front of the handguard. It’s said by many that any serious guns meant for combat should have pinned gas blocks, and at first glance it appears the PRI sight is held in place by two crosswise pins, front and back.

In truth, these aren’t two pins but rather four set screws which insert into recesses drilled into the barrel—like done with pins, except not all the way through. With this design, you would have to have all four pins not just loosen but fall out before your gas block could migrate. If the general design of these flip-up sights looks familiar, if you’re going, hey, those are a copy of the (X) sights…no. The PRI sights came first. Any sights on the market which look similar are a copy of the PRI sights.

Precision Reflex Inc. (PRI) has been in the AR business since 1979, and their products were innovative and successful enough that the folks at NSWC specced them on the SPR. Not just that, when the military came up with the idea of the SPR, PRI supplied several of the prototypes, although the guns sent to the field starting in 2002 were all built by NSWC.

And a quick note—guns meant for serious work should have back-up iron sights. That’s why you see them on the SPR and why you should have them on any AR you own meant for defense. Optics break.

When the SPR program was in its infancy and the R in SPR stood for Receiver, the SPR uppers were installed on older M16A1 or M4A1 lower receivers. However, standard GI triggers were not what you want in a precision rifle, and they were swapped out for aftermarket options. Officially, the KAC 2-stage precision trigger was chosen as the standard when the SPR became a complete rifle, but before and after that point SF trooper were installing various improved aftermarket triggers, preferring (in later years) the Geissele SSF.

Image of rail attachment to handguard and receiver
The ARMS Swan Sleeve provides a continuous rail surface from the lower receiver to the handguard. It is 0.45" taller than a standard flattop receiver, but traditional scope mounts work just fine. (Photo Provided by Author)

The ACE stock was specced for the original SPR. This was a skeletonized aluminum stock, and I suspect that it was chosen simply for its strength—it was durable enough to club a rhino unconscious. However, you can find photos of SPR top ends on lowers with adjustable carbine and fixed A1/A2 stocks. Many rifles, once they ended up in the hands of the SF troops, were customized with different grips and stocks.

The Ergo grip was specced for the SPR as well. Most likely many of you haven’t even heard of the Ergo pistol grip for ARs, even though it is still available. Let me slap you around with some knowledge, and a little history—the GI A2 pistol grip is designed to fit everyone, which means it fits no one. The finger groove on the front is in the exact wrong place unless you have fat banana fingers, and yet the grip itself is so skinny that unless you have tiny hands, you can wrap your trigger finger all the way through the trigger guard.

This isn’t what you want for precision shooting, or a precision rifle, where you should be working the trigger with the soft pad of the tip of your trigger finger. At the time, the Ergo grip was the only aftermarket grip available which added extra meat under the web of the shooter’s hand to help position their finger properly on the trigger. Before it was introduced, people were screwing spacers onto the back of their A2 grips in an attempt to make them more ergonomic (which is where the ergo in Ergo Grip comes from).

What about Magpul, you say? In 2000, the only product Magpul was making was the Magpul, the rubber thing you slip over your aluminum magazine to make it easier to pull out of its pouch. It wasn’t making stocks, grips, or magazines. The number of companies making accessories for ARs in 2000 was a fraction of what you see today. Heck, the number of companies making ARs in 2000 was a fraction of what you see today.

Charging handles displayed on white background showing different design shape
The military specced PRI’s Gas Buster charging handle (top) for the Mk 12 SPR. A standard GI charging handle is below. The Gas Buster has an oversize handle and you can see the internal curve which directs gases from a suppressed gun away from the shooter’s face. (Photo Provided by Author)

When the original Mk12 was designed, there were a few oversize charging handles on the market, but PRI’s Gas Buster was the only one specifically designed for use on suppressed rifles. Suppressors were far less common then than they are now, but if you’ve never shot an AR tipped with a sound suppressor you might not know just how much gas comes back into the upper receiver and into your face, shooting out (mostly) past the charging handle and straight up your nose, smelling of chlorine and smoke and cancer. The Mk 12 SPR was meant to run suppressed as often as possible, so equipping it with this charging handle only made sense. The Gas Buster features an internal curve on the front, which redirects gases away from the shooter’s face. It also has an oversize latch, so it is easier to work, especially while wearing gloves.

As I mentioned earlier, the SPR wasn’t so effective simply because of the rifle, but because it was a weapons system. The SPR was tipped with a sound suppressor, and topped with a variable power magnified optic, often a Leupold 2.5-8X, 3-9X, or 3.5-10X. LPVOs (low power variable optics) were not nearly as common back then as they are now, and big Army still preferred fixed-power riflescopes. An 8x or 10X top end magnification was huge increase over the 4X ACOG usually found in the field. The SPRs were usually outfitted with a bipod as well

In addition to the more accurate barrel, the SPR was fed the new 77-grain Mk 262 ammunition which was more accurate and provided better terminal performance. I spoke with Jeff Hoffman, President of Black Hills Ammunition, about the Mk 262 ammunition. It was the first operational (as opposed to training or competition) military contract for Black Hills. Their 5.56 match ammunition was accurate and consistent enough, from lot to lot, that they had contracts to load match ammunition for ALL the Armed Forces rifle teams. The Mk 262 ammo was developed at the same time and specifically for the SPR and was to be accurate out to 700 yards. The cartridge slightly evolved over time, ending up as the Mk 262 Mod 1, which features a 77-grain Sierra BTHP bullet with a cannelure to prevent bullet setback.

MK 12 SPR rifle displayed on stone shooting bench with fall forest background
The Mk 12 SPR (seen here is a new Mod 0 from Precision Reflex) is the most accurate AR-15 rifle ever fielded by our military. It sports an 18-inch heavy match stainless steel free floating barrel, and the military guns had match two-stage triggers. (Photo Provided by Author)

Actually, the military does not like the term BTHP (boat-tail hollow point) because of the (H)ollow (P)oint in the name, so the bullets in the Mk 262 cartridge are officially OTM—Open Tip Match—projectiles. I think the term OTM was invented for this ammunition, but it is accurate. That hollow tip is a result of the manufacturing process, and not designed to expand. But it does tend to break off upon impact. Hoffman told me, “The Mk 262 round is more accurate than M855, and more terminally effective—the commercial bullet tends to yaw upon impact and then break apart, even at increased distance [slower velocity], whereas M855 at that distance just pokes holes.” Not only does the tip break off after impact, the bullets would often fracture at the cannelure, producing multiple wound tracks.

Hoffman explained to me that, unlike standard military ammunition, the Mk 262 is loaded with flash-suppressant powder. When combined with a suppressor, it made soldiers equipped with SPR almost invisible at night while shooting. Invisible means no accurate return fire, which increases your lethality. The main difference between Mk 262 Mod 0 and Mod 1 is the cannelure on the bullet of the latter, to prevent setback in the case under recoil.

The development of the Mk 262 wasn’t without its hiccups. Hoffman told me, “I was contacted in 2003 or so. Some SEALs were training at Blackwater, and reported that they were having some reliability issues with the ammunition. I asked them, okay, what are the conditions? They said, rainy, cold, maybe thirty degrees, and the guns are really dirty. They cycle no problem when suppressed, but are having problems unsuppressed. Any idea what the problem is? And I told them, yeah, you built a gun with the same size gas port as a 20-inch gun, but cut two inches off the barrel.” But Hoffman is a perfectionist, did a little research and testing, and ultimately changed the powder to eliminate the problem.

The long, tapered 77-grain bullet in Mk 262 has a high ballistic coefficient (BC), which means it retains velocity better than the bullets found in standard military 5.56 ammo. It is also loaded hot even for 5.56 ammunition to get the highest velocity possible without sacrificing accuracy, and the longer barrel of the Mk 12 maximizes that velocity. I’ve been to Black Hills Ammunition, and whether they’re making ammo for the commercial market or to fulfill government contracts, it is made on small, individually-run in-line ammunition loading machines and physically inspected by a human at least three times before it ends up in a box.

Mk 12 next to ammo can of Mod 0 and Mod 1 ammo
Black Hills developed the Mk 262 Mod 0 and Mod 1 cartridges specifically for the SPR. It features a 77-grain bullet with a high BC and improved accuracy and terminal performance when compared to standard military ball. Mod 1-C is the commercial version of Mod 1, identical except not in stripper clips. (Photo Provided by Author)

Black Hills provides an accuracy guarantee with their Mod 1-C (Commercial) load, which is identical to the military load except it is not supplied in stripper clips. This ammunition will do 10-shot two-inch or better groups at 300 yards (guaranteed 0.64 MOA or better). In comparison, the military requirement for M855 is a maximum dispersion of 4 MOA from 100 to 600 meters. Hoffman told me that he contacted someone high up in SF during the height of the war on terror, wondering why the hell they were buying/using so much ammunition, as he knew there were only 200 SPRs in use.

The answer—everyone wanted the Mk 262 ammo. Everyone who could get it, whether or not they had an SPR, was using Mk 262. It was more accurate, and hit harder at every range, so SF troopers were using it in their M4s, and Marines and regular Army guys were trading whatever they could for it in the field. Out of standard M4s, the Mk 262 ammunition would produce groups half the size of standard military ammunition, but it was the vastly improved terminal performance that everyone was after.

At the beginning of this article, I mentioned how there are several different versions of the SPR—let’s dive into them. The original soon became known as the Mod 0. It sports the round PRI handguard, but there are several generations of the Mod 0. The differences are minute and have to do with small improvements to the handguard and SWAN Sleeve. The PRI handguards which have a barrel collar the same diameter as the carbon fiber handguard are the earlier ones. The later (current) gen handguards have a wider smooth aluminum collar, and that is referred to as the Mod 0 Gen 3.


The Mk 12 SPR Mod 1 is identical to the Mod 0 but for the handguard and sights. The round PRI handguard was replaced by a long KAC quad rail which also free floated the barrel. It adds a couple ounces over the PRI handguard. Also, the PRI flip-up sights were replaced by KAC models, the front sight moved back onto the handguard. Other than that, the Mod 0 and Mod 1 guns were identical. The Mod H, however, is an entirely different animal.

The Mk 12 SPR Mod H was only fielded by the U.S. Army’s 5th Special Forces Group. The Mk 12 SPR Mod H was the brainchild of Master Sgt Steve Holland with the 5th Special Forces Group based in Ft. Campbell, Kentucky, and he oversaw the project. He was also instrumental in the development of the 6.8 SPC cartridge, and PRI was heavily involved in the development of the 6.8 SPC cartridge as well. The idea was to create an SPR rifle that still provided more performance than an M4, but would be shorter and lighter than the Mod 0/1 SPR for more utility in urban settings.

Ironically, that was the recipe for the original SEAL Recce rifle. Kyle Defoor, a former SEAL, has talked at length on the subject, and I first interviewed him way back in 2012 about Recce rifles. According to him, “The original whatever you want to call them—Recces, SPRs, MK 12s [we usually just say “sniper M4”] had a 16-inch barrel, Leupold 2.5-10 and a PRI handguard. They were first used operationally in ‘93 in Somalia by our guys that were attached to our Southern brethren.”

black finished MK12  made by PRI displayed on white background
Precision Reflex Inc. (PRI) has been in the AR business since 1979 and involved in the SPR project from the beginning. Many of their proprietary parts were specced for the original builds.(Photo Provided by Author)

In regard to the SPR, he stated, “(It) went to 18 inches quite frankly because the big Army got involved. Most of us that have a lot of time on one think that 16 inches is better for a number of reasons: two inches does make a difference, especially with a (suppressor). Weight (it’s not pounds at this stage it’s ounces) and remember that balance has a factor here too.I’ve shot both together on the same range at the same time. I don’t really care what charts and scientists say, me and [my fellow SEALs] can hit just as good with 16 inch as 18 inch.

In 2007, several Precision Reflex Inc. employees drove down to Ft. Campbell and built the first 75 Mk 12 Mod H rifles. Ultimately, they built a total of 125 of these rifles for 5th Group. Perhaps “built” isn’t the correct term, as these new Mod H rifles were rebuilt out of older Mod 0 guns. For the Mod H, a very specific barrel was specced—a 16-inch stainless barrel made by Noveske. But the different length is only part of the story—this shorter tube sported a mid-length gas system and a 1:8-inch twist rate.

I was under the impression that U.S. Special Forces hadn’t specced a mid-length gas system on any of their guns until the creation of the URG-I (Upper Receiver Group—Improved) in 2018. And I was wrong. Compared to the shorter carbine-length gas system, a mid-length lowers the pressures in the system, and slows down your bolt, both reducing felt recoil and increasing bolt life.

Author shooting SPR Mod H against pole as rest
The shorter, lighter Mod H is still eight pounds empty even before you add an optic and loaded magazine, plus it sports a single-chamber muzzle brake, so recoil is minimal. (Photo Provided by Author)

The U.S. military went to a 1:7-inch twist in their rifles and carbines decades ago. A faster twist is considered better for longer/heavier bullets, as it stabilizes them more quickly. However, the 1:8-inch twist is considered by many people the best one-size-fits-all twist rate for the AR platform. While the intention was to use 77-grain Mk 262 ammo whenever possible, 5th Group wanted the Mod H to work well with bullets of all weights, because apparently their operators when overseas were often stuck using a variety of ammunition.

Under the handguard you’ll see the barrel has a low-profile gas block that is secured with two set screws. The Mk 12 Mod H barrel is tipped with the same OPS Inc. (now AE) muzzle brake that is threaded for use with their suppressor. Two inches behind the muzzle brake you’ll see the tapered collar on the barrel that is meant to stabilize/center the Ops Inc. Suppressor. The original SPR was specced to have a PRI flip-up front sight mounted directly on the barrel. With the shorter Mod H, that front sight was moved back onto the handguard. Both front and rear sights lock into place when up. The Mod H uses the exact same handguard as the Mod 0, but the rail is different.

With the Mod H model, the full-length ARMS #38 rail was replaced by a shorter Recce rail. It ties the receiver to the handguard but doesn’t extend the full length of the handguard. Overall, it is 11.5 inches in length, compared to the 19.5-inch length of the original rail. Forward of it you’ll see the handguard sports a lower rail. The rear/taller rail is meant for your daytime optic, and the forward lower rail is meant for your night vision/IR lasers. The Mod H upper receiver assembly is two inches shorter than the Mod 0, and according to my scale it is 9.8 ounces lighter, with all of that weight taken off the front half. That is a not-insubstantial amount of weight.

Unknown Soldiers holding Mk12 rifles  wearing military fatigues
Two unnamed SF troopers early on in the war on terror sporting Mk 12 SPRs in-country. With suppressors, scopes, and night vision, SPR-armed soldiers were able to rack up an impressive number of kills. (Public Domain Photo)

The U.S. military officially discontinued the Mk 12 SPR program in 2017, with that DMR role going to other weapons including the FN SCAR SSR. If you’re interested in the SPR Mod 1, Knight’s Armament doesn’t sell rifles, or complete uppers, but you can buy their Free Float Rifle RAS handguard found on the SPR Mod 1 and use it to build up a Mod 1 yourself. However, PRI has been selling Mod 0 SPR uppers/rifles since 2003, and also offers SPR Mod H components, upper assemblies, and complete rifles. Mod 0 and Mod H rifles and complete upper receiver assemblies are available from PRI in 1/7-inch or 1/8-inch barrel twists, in black or FDE Cerakote. The upper assemblies are identical to those used in combat, apart from barrel manufacturer. While all the Mk 12 Mod H SPRs fielded used Noveske barrels, PRI’s current Mod H sports a 416 stainless steel barrel from Douglas. Precision Reflex currently sells their Mod H complete rifles with B5 Systems Bravo stocks, and the Mod 0 with fixed A2 stocks or adjustable B5 Bravos.

SPR uppers are accurate and sturdy and tough—they were built for the mountains of Afghanistan and proved themselves in combat there—but what they aren’t is light. The heaviest single part in any AR is the barrel, and an 18-inch barrel with a heavy SPR profile weighs approximately 41 ounces. The Mod H complete upper receiver assembly from PRI weighs five pounds, 12 ounces, and a complete Mod H gun from them weighs eight pounds. Add a loaded magazine and an optic, and you’re already at or over ten pounds…before you add a bipod, or suppressor. The Mod 0 weighs 9.8 ounces more. But that weight (with or without the recoil reducing properties of the muzzle brake, depending on whether you’re using a suppressor) means that recoil is darn near zero. Not only are these rifles accurate, but that reduced recoil (when compared to a .308 or an M4) means you have the capability of rapid follow-up shots at surprising distance.

MK 12 broken down to show bolt and charging handle
SPRs are broken down and cleaned like any other AR. The Mod H is supplied from PRI with a standard carbine buffer. (Photo Provided by Author)

Plenty of stories made it out of Iraq and Afghanistan of the SPR in action. A two-man team surrounded in the dead of night scoring 75 kills with 77 rounds. Another duo killing 93 Taliban while expending just 99 rounds. A five-man Special Forces team looking for Scuds in Iraq was attacked by a reinforced Iraqi infantry company. Three men with SPRs covered the retreat back to the LZ. In doing so, they killed 167 Iraqi soldiers, with the rest either running away or surrendering. In truth, slapping an LPVO on an M4 would increase anyone’s performance shooting at distance, but once you add in a free floating match barrel, suppressor, a magnified optic, match trigger, and Mk 262 ammo, you have a formidable combination.

For accuracy testing on both rifles, I used the Nightforce ATACR 4-16X that I recently used out to 1,040 yards at a long range shooting course written up in these pages. 16X is all the magnification you need to shoot out to the maximum range of the Mk 262 cartridge, which is officially 700 meters…but has been used effectively beyond that.

While they weren’t available at the time, I feel a modern 1-8X or 1-10X LPVO scope might be a good choice for the shorter, lighter Mod H SPR—it gives you capability at CQB distances while having a top end magnification that allows you to reach out to the max effective range of the 5.56 cartridge. I mounted the Primary Arms Compact PLx 1-8X FFP on the Mod H upper. This to me seems a great match. The top magnification matches the 2.5-8X Leupold MR-T found on many SPRs overseas. The Mod H is short and light enough to use offhand (at least without a suppressor), but where it and its big brother shine is hammering targets at distance from a bipod. The lack of recoil means being able to spot your hits and provide rapid and accurate follow-up shots.


From my experience, and what I’ve heard, commercial SPR rifles will do MOA or better with most ammunition. The original SPRs fielded by the military reportedly would do eight-inch groups at 600 yards (1.3 MOA) which is more than acceptable for a DMR. For testing I used a number of different loads, including the Mk 262 Mod 1 load from Black Hills Ammunition. PRI doesn’t provide an accuracy guarantee but says that you can expect MOA or better performance from their SPRs with good ammunition. And that is what I found with my test guns.

Two targets showing groups fired from different Mk12 SPRs
(left photo) Black Hills Mk 262 Mod 1-C ammunition was the most accurate tested in the rifles, and while most of the time it did 0.75–1.0-inch MOA groups, occasionally it produced tighter ones like this 0.68 of an inch group out of the Mod H. (right photo) The military was saddled with OTM ammo because they don’t want to use expanding bullets, but there are better choices for personal defense including one of Tarr’s favorite’s Federal Fusion load, a bonded SP which hits hard and is darn accurate, too, consistently sub-MOA in the Mod 0. (Photo Provided by Author)

The only negative is that the PRI rifles are equipped with standard, GI-style trigger pulls, which means you’re going to have to work to shoot to the accuracy level the barrel promises. While the trigger pulls on the PRI guns are the best GI-style trigger pulls I’ve tested in quite some time (each 5.5 pounds with a rolling break), that’s a low bar to hurdle. I wish PRI offered a rifle closer to “clone” status, meaning a match two-stage trigger (the Geissele SSA would be a good choice) and the Ergo pistol grip…but in truth the people obsessed with building period-accurate clone rifles wouldn’t be satisfied with anything less than exact reproductions of fielded rifles, and the KAC 2-stage match trigger specced for the military SPR would add $300 to the cost of the rifle….

Precision Reflex was involved in the SPR program from day one, and apart from barrel manufacturer the SPR uppers they’re producing today are the same as our troops used overseas to such great effect. Even if you’re not into buying or building clones, the Mk 12 SPR is a functional piece of history, and the most accurate AR-15-pattern rifle ever fielded by our troops even before you start feeding it Mk 262 Mod 1 ammo. It is accurate, distinctive, and combat proven.

Data from Mk12 with 4 brands of ammo
(Data Provided by Author)

PRECISION REFLEX Mk 12 SPR MOD 0 SPECS

  • Caliber: 5.56 NATO
  • Weight: 8 lbs. 10 oz.
  • Overall Length: 37.75 in.
  • Receiver: 7075 T6 forged aluminum
  • Barrel: 18.0 in. Douglas 416 stainless steel, rifle-length gas system, 1/8 in. twist (1/7 in. available)
  • Gas Block: Integral with front sight,secured with four horizontal set screws
  • Muzzle Device: Ops Inc. (AE) muzzle brake
  • Stock: Fixed A2
  • Pistol Grip: A2
  • Handguard: PRI carbon fiber
  • Charging Handle: PRI Gas Buster
  • Trigger: Single stage, 5.5 lbs (as tested)
  • Sights: PRI flip-up front and rear
  • Finish: FDE Cerakote (black available)
  • Accessories: Hard case
  • MSRP: $2,220
  • Contact: (419) 629-2603, PrecisionReflex.com
data on Mk12 SPR Mod H with 4 types of ammo
(Data Provided by Author)

PRECISION REFLEX Mk 12 SPR MOD H SPECS

  • Caliber: 5.56 NATO
  • Weight: 8 lbs.
  • Overall Length: 33.0 in. (stock collapsed), 36.5 in. (stock extended)
  • Receiver: 7075 T6 forged aluminum
  • Barrel: 16.0 in. Douglas 416 stainless steel, mid-length gas system, 1/8 in. twist (1/7 in. available)
  • Gas Block: Compact
  • Muzzle Device: Ops Inc. (AE) muzzle brake
  • Stock: B5 Systems Bravo
  • Pistol Grip: A2
  • Handguard: PRI carbon fiber
  • Charging Handle: PRI Gas Buster
  • Trigger: Single stage, 5.5 lbs (as tested)
  • Sights: PRI flip-up front and rear
  • Finish: Black, FDE Cerakote available
  • Accessories: Hard case
  • MSRP: $2,099
  • Contact: (419) 629-2603, PrecisionReflex.com



GET THE NEWSLETTER Join the List and Never Miss a Thing.

Recommended Articles

Recent Videos

KelTec releases their PR57 pistol and SUB2000 rifle in 5.7x28mm as the demand grows for more firearms in this unique and...
Gear

Firearms News Gets the Rundown on Burris's New XTR-PS

KelTec releases their PR57 pistol and SUB2000 rifle in 5.7x28mm as the demand grows for more firearms in this unique and...
Guns

SDS Arms Releases New Tactical Shotgun Lineup

KelTec releases their PR57 pistol and SUB2000 rifle in 5.7x28mm as the demand grows for more firearms in this unique and...
Guns

New Hunting Shotguns Available in Mossy Oak and Realtree Camo

KelTec releases their PR57 pistol and SUB2000 rifle in 5.7x28mm as the demand grows for more firearms in this unique and...
Guns

Inglis MFG Launches New P35 Pistol

KelTec releases their PR57 pistol and SUB2000 rifle in 5.7x28mm as the demand grows for more firearms in this unique and...
Guns

MAC Firearms unveils New 5' Comp Barreled Double Stack 1911

KelTec releases their PR57 pistol and SUB2000 rifle in 5.7x28mm as the demand grows for more firearms in this unique and...
Gear

New Iron Lady Gun Safes from ATI

KelTec releases their PR57 pistol and SUB2000 rifle in 5.7x28mm as the demand grows for more firearms in this unique and...
Guns

American Tactical Releases GSG Anniversary 1911 Pistol

KelTec releases their PR57 pistol and SUB2000 rifle in 5.7x28mm as the demand grows for more firearms in this unique and...
Gear

First Look at ATI's new Rukx Rifle Case

KelTec releases their PR57 pistol and SUB2000 rifle in 5.7x28mm as the demand grows for more firearms in this unique and...
Guns

American Tactical Showcases their Latest GSG-16 22 LR Pistol and 410 Bull Dog Shotgun

KelTec releases their PR57 pistol and SUB2000 rifle in 5.7x28mm as the demand grows for more firearms in this unique and...
Guns

ATI Launches New Double and Triple Barreled Shotguns for 2025

KelTec releases their PR57 pistol and SUB2000 rifle in 5.7x28mm as the demand grows for more firearms in this unique and...
Gear

New Glock 17/19 18-Round Magazines Offered by Mec-Gar

KelTec releases their PR57 pistol and SUB2000 rifle in 5.7x28mm as the demand grows for more firearms in this unique and...
Guns

KelTec Launches PR57 Pistol: The Best and Lightest 5.7

Firearms News Magazine Covers Print and Tablet Versions

GET THE MAGAZINE Subscribe & Save

Digital Now Included!

SUBSCRIBE NOW

Give a Gift   |   Subscriber Services

PREVIEW OUR CURRENT ISSUE

Buy Digital Single Issues

Magazine App Logo

Don't miss an issue.
Buy single digital issue for your phone or tablet.

Get the Firearms News App apple store google play store

Other Magazines

See All Other Magazines

Special Interest Magazines

See All Special Interest Magazines

GET THE NEWSLETTER Join the List and Never Miss a Thing.

Get the top Firearms News stories delivered right to your inbox.

Phone Icon

Get Digital Access.

All Firearms News subscribers now have digital access to their magazine content. This means you have the option to read your magazine on most popular phones and tablets.

To get started, click the link below to visit mymagnow.com and learn how to access your digital magazine.

Get Digital Access

Not a Subscriber?
Subscribe Now

Enjoying What You're Reading?

Get a Full Year
of Guns & Ammo
& Digital Access.

Offer only for new subscribers.

Subscribe Now

Never Miss a Thing.

Get the Newsletter

Get the top Firearms News stories delivered right to your inbox.

By signing up, I acknowledge that my email address is valid, and have read and accept the Terms of Use