Seekins SP10 Review: Testing the AR-10 Used by Delta Force

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The Seekins SP10 is the choice of professionals. This high-end AR-10 pattern rifle has been fielded since 2019 by the United States Army Special Operations Command (USASOC), specifically within the Combat Applications Group (CAG), more commonly known as Delta Force. They selected the Seekins SP10 after extensive testing, basing their decision on its superior accuracy, softer recoil, long barrel life, and demonstrably better reliability compared to other gas guns they evaluated. But I wasn’t about to take Delta Force’s word for it, so I ordered my own to see what all the fuss was about. Seekins SP10 Specs See It Cartridges: 6.5 Creedmoor (tested), also 6mm Creedmoor and .308 Win. Barrel: 22 inches, 1:8 twist, threaded 5/8-24 Stock: Magpul PRS Gen 3 Trigger: Triggertech Single-stage Duty AR; 3 pounds 9 ounces (measured) Handguard: 15-inch SP3R Gas System: Full-length Weight: 11 pounds, 7 ounces (measured) Price: $2,795 Key Features Ambidextrous controls: safety, magazine release, bolt stop Adjustable stock Free-float barrel High-mass bolt carrier group Adjustable gas block M-Lok slots on handguard and buttstock Full length Picatinny rail Review Highlights Flawless operation Great ergonomics Smooth action, soft recoil Accuracy: 0.650 inches (average of ten best 5-shot groups) Configuration as Tested Scope: Nightforce 7-35×56 ATACR Scope Mount: Seekins Hit Precision Mount LRF   Bipod: Warne Skyline Lite Suppressor: Elite Iron STFU Top Performing Ammunition Freedom Munitions 140-grain HPBT (0.726-inch average) Sierra 140-grain Tipped Gameking (0.824-inch average) Sierra 140-grain Matchking (0.906-inch average) Federal Gold Medal Center Strike 140-grain OTM (1.018-inch average) Two of the groups turned in with Sierra 140-grain Matchking ammo. John B. Snow Seekins SP10 Overview To appreciate what the SP10 brings to the party you need to delve into the details of how it is constructed. We tend to lump AR rifles together, which is an understandable reflex given their Lego-like ability to mix and match parts. And, without doubt, we’ve seen many AR-15s and AR-10s that are indistinguishable other than cosmetic differences in their furniture. But as they say, the Seekins SP10 isn’t like the other girls. The extension on the upper supports the handguard and allows for a free-floating barrel. John B. Snow Free-floating Barrel One shortcoming of the original AR design is how the barrel, receiver, and handguard connect. Instead of threads, AR barrels have a smooth barrel extension that surrounds the chamber. The extension, which has a raised collar, slides into the AR upper until the collar comes in contact with the upper. A barrel nut—which slides over the barrel—is then screwed onto the threads on the upper, pinching the barrel and upper together. AR handguards typically attach to the barrel nut in some fashion. In essence, this makes the barrel nut the glue that holds the upper, barrel, and handguard together. As a result, pressure on the handguard, such as when loading a bipod or shooting with a sling, can shift the point of impact and degrade accuracy. A POI shift can also occur when mounting accessories to the handguard like thermal/IR units, weapon lights, or laser rangefinders. Various designs have sought to work around this, but no one has engineered a better solution than Seekins. The upper on the SP10—similar to this AR-15 sized iRMT-3 but without the forward assist—is machined with a large triangular mounting surface that surrounds, but does not touch, the barrel and barrel nut. That triangular element mates with the triangular handguard, which is held in place with 10 Torx-head fasteners. This gives the SP10 a truly free-floating design and is one of the main reasons for the rifle’s excellent precision. The size of the mounting surface also adds stiffness to the rifle, reducing flex within the upper and creating a rock-solid connection between the handguard and upper. This augments the rifle’s precision and durability as well. The bolt carrier group for the Seekins SP10 (below) is much larger and heavier than the one used in the DPMS G2. John B. Snow Bolt Carrier Group One of the qualities we look for in a good rifle is “shootability.” This catch-all term covers a lot of ground, but a major component is how a rifle recoils and the ability of the shooter to manage it. Ideally, we want a rifle that helps the shooter stay on target, so they can see their impacts and make quick and accurate follow-up shots. The bolt carrier group (BCG) is the main moving part on AR rifles and the speed at which it moves plays an outsized role in how the shooter experiences recoil. BCGs: Light and Fast vs Slow and Heavy Broadly speaking there are two schools of thought on BCGs. One is to reduce their mass to trim weight and make the rifle easier to carry. A good example for large-frame ARs was the DPMS G2, which was built around a shorter and narrower BCG with a smaller outer diameter than a typical AR-10. This was a revolutionary design with respect to making an AR-10 more portable for hunting applications. A more recent example is Ruger’s SFAR. In order for a rifle with a light BCG to be reliable, however, it has to move back and forth more quickly in the action. We need to make sure the BCG is generating enough energy to strip rounds from the magazine and feed them into the chamber. Because energy is a function of mass times velocity squared, an increase in BCG velocity results in a disproportionate increase in felt recoil. A fast and light BCG will also be prone to more reliability issues. The Seekins SP10 goes the other route. The BCG on the SP10 is hefty. Mine weighs in at 17.95 ounces versus the 13.4-ounce weight in the DPMS G2. Seekins did this on purpose, of course, so that the action can cycle at a slower speed and dramatically reduce felt recoil while improving reliability. While shooting the SP10 you can really feel the relaxed “cha-chunk” motion of the BCG, which is less jarring than a higher-speed system. To drive the BCG back into battery the Seekins SP10 uses a flat coil spring, rather than a standard round-wire spring. The spring smushes down more compactly, so it can have more coils in the same space to exert more force on the BCG. Compared to my AR-10s with round coil springs, the SP10’s flat-wire spring has 42 coils versus 37. Adjustable Magpul PRS Gen3 Stock The SP10 comes with Magpul’s PRS Gen3 stock, which was designed for precision rifle applications. It is stout, rigid, and has machined aluminum thumbwheels that control the length of pull and height of the cheekpiece. The LOP extends up to 1.5 inches and the cheek piece can be raised up to an inch. The thumbwheels turn easily by hand but are stiff enough (and have positive ball-detent clicks) so that they won’t move until you want them to. The adjustments are incredibly granular. The wheel controlling LOP has 42 clicks of travel, meaning each click will move the butt pad 0.036 inches. The stock has one QD sling attachment point behind the pistol grip and another QD cup/sling loop mount at the rear. Both can be moved from one side of the stock to the other, which is one of the many ambidextrous features on the rifle. The underside of the stock has two M-Lok slots to mount a monopod, bag rider, or other accessory. The flat surface on the stock’s underside rides a rear bag very well, and I like how it is angled. Thanks to its geometry I can make quick vertical adjustments to my crosshairs by shifting my rear bag forward or back. The cushy recoil pad has two readily accessible Allen head screws that when loosened allow the pad to move up and down. Taken together, these adjustments allow for a customized fit that should work for nearly any shooter in any situation. The Magpul PRS Gen3 stock on the Seekins SP10 has thumbwheel adjustments for length of pull and cheekpiece height. John B. Snow SP3R Handguard I like handguards with a flat underside for any AR I’m using for precision rifle work. The 15-inch handguard on the SP10 (which is roughly triangular shaped) is one of the best in my opinion. It has a broad flat bottom with seven M-Lok slots along its length, and flats on either side with seven M-Lok slots as well, for 21 in total. Each flat also has two QD attachment points, one at the front and another at the rear, for six altogether. Perched atop the handguard is a Picatinny rail that covers all 15 inches and that mates seamlessly with the Pic rail on top of the upper. Ambidextrous Controls The Seekins SP10 has thoughtfully designed controls that are fully ambidextrous. The safety, magazine release, and bolt catch are all well positioned and easy to run from either side. One way you can see the detail that went into the SP10’s engineering is how the controls take about the same effort to run, whether manipulating them from the right or left side. The contact surfaces on the controls are machined with a broad checkering pattern that gives positive feedback to your fingers, provides a bit of grip, and looks attractive. The 45-degree safety operates smoothly and is easy to move between safe and fire with your thumb on one side or your trigger finger on the other. Controls on the Seekins SP10 are ambidextrous and ergonomic. John B. Snow Running the Seekins SP10 Everything I sketched out above in praise of the rifle’s design becomes manifest when the shooting starts. The rifle is blessed with excellent ergonomics that make shooting it a pleasure. At no time during my evaluation did I feel I was fighting against the rifle. Running it feels intuitive and nearly effortless. I started shooting without a suppressor attached to get a feel for it in naked trim. Even without the recoil- and noise-reducing benefits of a can, the SP10 is incredibly well mannered. The crisp single stage trigger, overall rigid construction, and comfortable stock—combined with the soft recoil impulse—makes the rifle a snap to control. I shot a handful of groups with it this way and then transitioned to some positional work at my range. From the get-go the rifle was churning out sub-MOA groups and a couple of them were at a ½ inch or below, which will give any rifle shooter the tingles. With that baseline established, I screwed on a .30-caliber Elite Iron STFU suppressor and continued. The suppressor enhanced my control over the rifle and didn’t have a negative impact on group sizes. However, the rifle was severely overgassed with the can on board, and I could feel the increased blowback on my face with every trigger pull. I adjusted the gas block, pinching down the gas to nearly the lowest setting, and that helped get the bolt speed back to where it needed to be. Make no mistake, this rifle is hefty. With the suppressor, my Nightforce 7-35×56 ATACR, and a Warne bipod it weighs 16.25 pounds. I will bet, however, that any temptation you might have to moan and grumble were you forced to hump it around all day would dissipate the moment you got behind the gun and began shooting. For me, the juice is worth the squeeze when considering the benefits of the rifle’s weight—accuracy, reliability, recoil management—against the drawbacks. Takedown Procedure After I put about 80 rounds through the rifle, I could feel the action getting a bit sluggish. I never had a failure to feed or cycle, but the bolt wasn’t dropping on a fresh magazine with the same enthusiasm as before. The SP10 has a standard AR-10 two-pin takedown system, though one cool touch is the shape of the head on the front pin which is sculpted to flow with the contours in the lower. I added a bit of CLP to the AR’s BCG and, PDQ, the rifle was running A-okay. That did make me reflect on whether a ban on acronyms would be in everyone’s best interest, however. Reliability The bolt head on the Seekins SP10 features dual plunger ejectors. John B. Snow I’ve put about 300 rounds through the rifle in total so far, all of it quality 6.5 Creedmoor stuff. To date, I’ve run seven different loads in the rifle, with no issues. Seekins put a lot of effort into fine-tuning the rifle to enhance reliability. The lugs on the bolt are slightly radiused and chamfered to help them go in and out of a battery with less effort and to retard the inevitable wear that AR-10 bolt lugs experience. The bolt face is equipped with dual plunger ejectors to kick empties free with authority, and Seekins tweaked the dimensions of the ejection port to minimize the chance of a malfunction. The machined aluminum upper and lower wear a tough anodized coating for durability. The BCG has a nitride finish, while the bolt is DLC coated. All of this gives best-in-class protection from corrosion and hard use.  Seekins SP10 Accuracy The SP10 is known for its accuracy, and my rifle certainly lives up to that reputation. In particular it really likes 140-grain match ammo. The 5-shot groups of Freedom Arms 140-grain HPBT ammo I’ve put through it average 0.726 inches; with Federal Center Strike 140-grain OTMs the average is 1.018 inches; and Sierra 140-grain Matchkings average 0.906 inches. For a hunting load, the Sierra 140-grain Tipped Gameking performed extremely well, too, averaging 0.824 inch 5-shot groups. The velocities from the 140-grain match loads has been consistent, right around 2565 fps from the 22-inch barrel. The 140-grain Tipped Gamekings have a bit more pep, stepping out at 2630 fps. I also ran Hornady 143-grain ELD-X (1.472 inch average); Barnes 120-grain TTSX (2.808 inch average); and Barnes 127-grain LRX BT (1.815 inch average). While those results are nothing to write home about, that’s about what those particular lots of ammo have been doing in other 6.5 Creeds in my collection. While I had no issue with the rifle-length gas system on my SP10, Seekins has since switched over to a plus-1.5-inch gas system, which should make the rifle run in an even more bomb-proof manner. Seekins SP10 vs SP10-M Technically, the SP10 that our Delta Force commandos use is the SP10-M, whereas the model I tested was the standard SP10. One meaningful difference between the two is the gas block. The gas block on the SP10-M has a throw lever so that it can be adjusted without tools. This allows you to tune the rifle on the fly in case you need to get more gas into the system (as when the rifle gets dirty from prolonged use) or less (such as when you thread on a suppressor). My rifle came with a Seekins Low Profile Adjustable Gas Block, which has two screws you manipulate to regulate the amount of gas. There’s a set screw on the front of the gas block that, when loosened, lets you turn the screw on the side of the gas block to regulate the pressure used to run the action. The other difference between CAG’s SP10s and mine is the chambering. CAG has been running guns in .260 Remington, whereas the standard SP10 comes in 6.5 Creed, which I tested, as well as 6 Creed and .308 Winchester. Don’t be surprised if CAG moves away from the .260 Remington in the future in favor of the 6.5 Creedmoor or another cartridge. Seekins SP10 Pros Excellent accuracy Great ergonomics Easy to control Extremely reliable Seekins SP10 Cons Expensive Heavy Seekins SP10 John B. Snow Final Thoughts on the Seekins SP10 The Seekins SP10 is an impressive rifle. It is as well thought out as any AR-platform gun on the market and is smartly configured for its intended mission—which is to be able to place fast, accurate fire on distant targets under trying conditions. I only have a handful of rifles in my arsenal that I use as a baseline to test the accuracy of 6.5 Creedmoor ammunition—among them the Sako TRG 22 A1, the Accuracy International AXSR, Proof Research Conviction, and a few custom builds. The Seekins SP10 is the only gas gun I include in that category, which is as good a testament as I can offer regarding its merits. As time goes on I’m going to add data to this review, highlighting the results I get with other loads and adding more observations on the rifle. But rest assured, if you want to own and shoot one of the most capable gas guns made, the Seekins SP10 won’t disappoint.