Rock Island Armory STK100 Striker-Fired 9mm Pistol Review: Beyond Expectations

The Rock Island STK100 9mm pistol is optics-ready, all metal, has a low-bore axis, takes Glock mags and has a great trigger — for less than $600! Here's a full review.

March 20, 2022 By Joe Kurtenbach

Armscor Precision International is an intriguing company within the American firearms market. With manufacturing operations in both the Philippines and the United States (Montana and Nevada), the company is regarded as the most prolific maker of Model 1911-style pistols. However, few gun enthusiasts know that Armscor traces its lineage back to a turn-of-the-century photo printing shop in downtown Manila.

Squires, Bingham & Company was founded in 1905 by a pair of namesake English expatriates. It gradually expanded its offerings to include a premier selection of sporting goods such as firearms and ammunition. Just prior to World War II, with the threat of Japan’s invasion looming, Don Celso Tuason purchased the business and survived hostilities by operating the company as a haberdashery, a purveyor of men’s apparel and accessories. He later helped his homeland rebuild and became one of the first post-war firearms manufacturers in the Philippines.

Through Tuason’s descendants, Armscor remains an innovative and enterprising gunmaker today. In fact, it is still privately owned by the Tuason family. Martin and Lisa Tuason, Celso’s grandchildren, lead the company as its CEO and vice president of marketing, respectively. In 1980, the company was reorganized as “Arms Corporation of the Philippines,” or “Armscor.” By 1985, Armscor Precision International was established in Pahrump, Nevada, and acquired Rock Island Armory (RIA) soon after.

Attention Getters

Armscor is a familiar brand for its value-priced M1911s. It’s true: Armscor makes and sells more M1911s than any other brand today, but there is more to the company.

Rock Island Armory STK100 Striker-Fired 9mm Pistol, right side (Mark Fingar photo)

In 2016, the .22 Tuason Craig Micromagnum (TCM) was launched as a high-velocity and low-recoil self-defense option. It’s a clever bottle-necked .22 cartridge designed around a 5.56 NATO case. It, and the shorter .22 TCM 9R — designed for use in Glock magazines — was featured in Guns & Ammo’s April 2016 issue.

Armscor also imports its VR series of tactical, magazine-fed semiautomatic shotguns to the U.S., as well as a variety of pump-action, over-under and single-shot shotguns. You’ll also find various revolvers, pistols, ammunition and components in the lineup.

Rock Island Armory STK100 Striker-Fired 9mm Pistol, left side (Mark Fingar photo)

While Armscor currently builds nearly all of its guns in the Philippines — and sells them stateside under the RIA brand, Armscor has also invested in “Made in America.” It now has an ammunition factory in Stevensville, Montana, and headquarters and production facilities in Parhump, Nevada. I think this “dual-citizenship” is the characteristic that makes Armscor so interesting. It’s a company that truly cherishes its heritage, yet also appreciates the advantages and freedoms offered by the United States.

Rock Island Armory STK100 9mm Pistol Field Stripped — With the magazine removed, the STK100’s field-stripping procedure is familiar to most who have disassembled other striker-fired pistols. (Mark Fingar photo)

First Strike

Despite its history in making hammer-fired pistols, Armscor was not oblivious to the 9mm striker-fired pistol trend. The recent expiration of patent protections for certain striker-fired semiautomatics — Glock — opened the door for many “new” pistol to borrow a proven and reliable operating system and make it their own. It also presented Armscor the opportunity to refine the operating system and engage its engineers in designing a gun that’s desired among competition shooters: An all-metal pistol that’s optics ready, features a low bore axis, great trigger, is reasonably priced and reliable. With that, it’s time to meet the RIA STK100 in 9mm.

Rock Island Armory STK100 9mm Pistol Accessory Rail — The accessory rail on the dustcover generously offers three slots to accommodate most lights and lasers. (Mark Fingar photo)

Metal Framework

The first characteristic that sets this gun apart from Glocks and clones is the anodized aluminum frame. The primary advantage, as fans of the M1911 and other metal-frame guns can agree, is that the added weight helps absorb recoil energy, which makes the shooting experience easier on the hands. It also allows for faster recovery of one’s sight picture, resulting in quicker follow-on shots. The unloaded weight of the STK100 is around 30 ounces, which is a few ounces heavier than comparable polymer-frame models.

Rock Island Armory STK100 9mm Pistol Grip — The grip design features an extended beavertail, as well as a wonderfully textured and grooved touchpoints. Armscor indicates that the tactile grip is angled closely to an M1911’s. (Mark Fingar photo)

Armscor opted for a two-piece clamshell design to build the frame. Screws — not pins — hold the lower halves together and the fire-control components in place within.

Rock Island Armory STK100 9mm Pistol Metal Frame — Two screws at both ends of the triggerguard reveals that this pistol is assembled on a two-piece, aluminum clamshell frame. (Mark Fingar photo)

Starting at the front, the frame includes a three-slot rail section for mounting lights or lasers. The triggerguard is a round design that has an undercut at the rear for a high grip, and the grip texturing features a point-and-dimple pattern on the sides, and horizontal grooves around the frontstrap. There are downward slanted grooves on the backstrap, beneath the extended beavertail. The rear is effective at protecting against slide bite and helps to promote a high grip.

Rock Island Armory STK100 9mm Pistol Glock Magazines — The STK100 feeds from 17-round Glock-pattern magazines, which means that they’re affordable, reliable, and you can find spares easily. (Mark Fingar photo)

Most interesting about the frame is that it accepts Glock 17-pattern magazines. Magically, it somehow features a grip angle closer to an M1911. It must have taken some engineering wizardy to fit the raked Glock magazine into the comparatively vertical grip and have ammunition properly aligned for function, but the result is a gun that feels similar in hand and possesses the heft a John M. Browning’s Hi-Power design.

As far as controls, the STK100 mirrors the typical Glock configuration, but there are some upgraded components. For example, the non-reversible magazine release is slightly extended and more pronounced, as is the left-side-only slide-lock/release lever. The bilateral takedown tabs still facilitate disassembly, and the trigger features the familiar center-lever safety.

Rock Island Armory STK100 9mm Pistol Rear Sight — The rear sight is fixed, serrated and low. It is screwed onto an optic-cut coverplate that is removed when attaching a red dot sight. (Mark Fingar photo)

Up Top

The slide is machined from billet steel and sports a Parkerized black finish. Noticeable are the front and rear cocking serrations, as well as the lightening cuts that give it a racy appearance. (Some believe that these slide ports improve function and handling during recoil, also.) It mounts to the frame by sliding along two sets of rails. These are noticeably longer than most comparable polymer pistols. Hence, the slide-to-frame fit is good and tight, and similar to high-end production M1911s or SIG Sauer’s all-metal P-series pistols. The fitment is not custom-grade or bullseye-match tight, but there is no tilt or wobble. Slide travel is smooth and level. It’s also worth noting that the slide and barrel ride visibly lower than many pistols, and the low bore-axis is another feature designed to mitigate the negative effects of felt recoil.

Rock Island Armory STK100 9mm Pistol Slide — The slide is billet machined and features lightening cuts above the front serrations. (Mark Fingar photo)

Sights consist of a serrated, black, notch-style rear and a white-dot front. The front sight follows the Glock-pattern and should be interchangeable. On the other hand, the rear sight is integrated into a cover plate that, when removed, reveals a mounting surface for either a Vortex Venom, Crimson Trace CTS-1250, or similar-footprint sight.

Crimson Trace CTS-1250: Check Price

Like the frame’s fire-control assembly, the striker assembly and backplate access, as well as the firing pin safety, follow the familiar Glock pattern. Further, the 4 1/2-inch barrel is chambered for 9mm and features 1:16-inch twist-rate rifling. It is definitely a departure from the common 1:10-inch twist rate, but not as loose as the 1:18.75-inch twist that had some traction in earlier generations of 9mm pistols. A captured recoil spring and metal guiderod assembly round out the slide’s subcomponents.

Rock Island Armory STK100 9mm Pistol Fire Control — Though the internal fire-control assembly looks as if they were designed for a G17, however, they are unique to the STK100. (Mark Fingar photo)

Shots Downrange

There are plenty who believe that Armscor and RIA offerings as guns are designed to compete on price alone. Then there are people who have shot them.

Rock Island Armory STK100 Pistol Getting Fired — “The first rule of gunfighting is to have a gun and the handgun is the one you are most likely to have when danger presents itself.” — D. Spaulding

Make no mistake, Armscor has earned ISO 9001 quality management certification, which makes it a very serious manufacturer of firearms. While the company may not always use premium-grade raw materials or exhibit high-level finishes, its guns will run; in my experience, they are often more reliable than competitive models that cost two or three times as much.

Still, given that this is a new platform, and many reading this review may not have had a chance to shoot earlier pistols, I set out to test this pistol under stressful conditions and let the chips fall where they may. To that end, I enrolled in a three-day Handgun Combatives course taught by Dave Spaulding (handguncombatives.com). Harsh? It was summer — in central Virginia.

Author Shooting the Rock Island Armory STK100 Pistol — The author evaluated the STK100’s reliability through the rigors of Dave Spaulding’s three-day Handgun Combatives course.

Three days of brutal heat and humidity. There was sweat, dirt and fouling. More than 800 rounds of 9mm was sent downrange through the STK100. Add to this the fact that I shot the entire class using a concealed, appendix inside-the-waistband (AIWB) set-up. I did this for both the training value and to see if the gun was too big or too heavy for everyday carry. Because no STK100-specific holsters were available, I ordered a Surefire X300U-B light (surefire.com, $329) and a Tier 1 Concealed MSP Pro holster system (tier1concealed.com, $160) with magazine carrier, which was named for instructor and AIWB proponent Scott Jedlinski’s Modern Samurai Project (modernsamuraiproject.com). I also equipped the STK100 with a Crimson Trace CTS-1250 red dot for use throughout training.

In sum, the conditions were absolutely awful. Temperatures ranged from the high 80s to high 90s, plus 60 to 80 percent humidity. Don’t believe me? Ask Richard Nance, G&A’s Gun Tech editor. Nance was in attendance as an assistant instructor, and I thought the California boy was going to melt in Virginia’s summer swelter.

The gun performed flawlessly. Further, it exhibited outstanding accuracy and was very fast on follow-up shots. Its performance was a real credit to the balance of features, which include those designed to improve control and mitigate recoil.

There were two minor stoppages, one each toward the end of the first and second days. Both were quickly cleared with “Tap-Rack” procedures, which didn’t surprise me. This was on-par with the performance of a variety of Glock pistols, SIGs and Smith & Wessons also in attendance.

One noteworthy accomplishment for shooter and gun alike was our performance of Spaulding’s three-round Fade Back Drill, which was shot at the start of each day. In the drill, shooters fire three shots at a 3- by 5-inch target at increasingly longer distances: 5, 10, 15, 20 and 25 yards. I shoot this drill regularly in my own practice, usually pulling two or three shots just off target at the longer ranges. Trigger control is usually the primary culprit for misses. However, during the course, I recorded my first clean run and missed only one shot in each of the other runs. That’s marked improvement, and I think the weight of the gun and smooth trigger action aided accuracy at the extended ranges.

The pistol’s excellent performance continued at my home range during accuracy testing later. Again, this is not to suggest the STK100 is a bullseye gun; it exhibited very good 25-yard accuracy across a range of ammunition types and weights. My full results are tabulated in a chart, but the overall average of 25 five-shot groups was 3.37 inches. Considering the variety of projectiles, this is outstanding and, again, a credit to the trigger’s design.

To dwell on the topic of the trigger, the STK100 I had for this evaluation had a trigger-pull weight of 5 pounds, 10 ounces, which was averaged from 10 pulls using a Lyman digital gauge. Too, the pulls were consistent; there were no more than a 3- to 4-ounce difference registered from shot to shot. For comparison, I gauged the trigger on my Gen5 Glock 19. In my opinion, it has the best of the factory Glock triggers. That trigger measured 5 lbs., 15 ozs., and produced larger variances. Despite being the best Glock trigger to date, largely free from grit and hitches, the G19 still has the heavy and sometimes inconsistent wall where the transfer bar disengages striker block. RIA started its design essentially Glock Gen3-pattern internals, but drew on experience to tweak, refine and smooth the trigger design. RIA’s engineers managed to put together a fine rendition of a striker-fired trigger for the STK100.

Constructive Criticism

After such a positive evaluation experience, I have no doubt that the RIA STK100 is a very good pistol. That said, the sample size for my testing was exactly one. With more than 1,600 rounds downrange between the training course, accuracy evaluations and my own shooting — all during the COVID ammo craziness — I think Guns & Ammo can safely claim to have conducted one of the most extensive evaluations of the pistol to date. (Allow me to thank Remington for assisting me in sourcing ammunition!) All told, the STK100 performed remarkably well. It has earned my trust and admiration.

Was it without fault? Absolutely not.

Optic Mounting

Let’s cut to the chase. The biggest question mark I have about the STK100 is its optic-mounting capability. The pistol comes optic ready thanks to a removable rear-sight plate held in place by two top-mounted Allen-head screws. This is a standard feature; no upgrade required. While RIA earned high marks for including the ability to mount a red-dot sight, it did not do a great job of explaining what optic brands and models actually attach to the gun. (Don’t fret, I’ve got you covered.)

Rock Island Armory STK100 Pistol Red-Dot Sight Options — Removing the optic cover plate reveals that the slide will accept a number of popular sights. For this review, the author tested the STK100 with Crimson Trace’s CTS-1250 open reflex sight. (Mark Fingar photo)

The mounting arrangement is designed around the Vortex Venom micro red dot (vortexoptics.com, $350), which shares its 14mm footprint — measured mounting screw to mounting screw — with optics including the Crimson Trace CTS-1250 that I used extensively for this test. It also accepts the JPoint sights (jprifles.com, $300). These three options, at least, will mount securely to the STK100, but your compatibility may vary with other 14mm-footprint optics. Here’s why: Beneath the sight plate, the mounting surface is flat and smooth, save for two internally threaded bosses. These bosses serve as both recoil lugs and mounting screw attachment points. The mounting surface, though, is designed around the Venom red dot, and provides a snug fit for that sight. Optics that are longer or beefier in construction may be too large for the STK100. Additionally, the bosses are intended to engage the bottom of the sight as lugs, so the optic’s mounting ports must be large enough to accept them. Optics built on the 14mm footprint, but designed for four-corner-style recoil bosses and mounting plates (such as the Hex Dragonfly I tried) will not fit over the STK100’s mounting bosses. To be clear: Optics built around the Trijicon RMR, SRO or Leupold DeltaPoint Pro footprints are not compatible.

Besides accommodating only a specific optic style, my other concern about the slide-mounting arrangement is the loss of the rear sight when attaching an optic, which is integral to the cover plate. My belt and suspenders may be showing on this one, but I still prefer to have iron sights on my pistols, even with my requisite red dot. Sure, even a dead red dot can be used as an emergency muzzle-direction aperture — especially at short range. And, the front sight here is a Glock-pattern unit, so a taller option could easily be swapped. Still, if I had one gripe, it would be that the gun is not designed to accommodate both an optic and irons.

Unusual Twist Rate

Some will have concern that the barrel’s 1:16-inch rifling might produce poor accuracy, particularly with heavier bullets that generally require fast twist rates to stabilize. I tested the STK100 with five different loads and bullet weights; they ranged from 115 grains to 150 grains. According to my results, the too-slow rifling theories did not hold up. The two 124-grain loads had the best single groups, and all the averages were comparable. The heaviest load, a 150-grain Federal Syntech, did post the largest group and largest average, but considering its unusual construction and the fact that Winchester’s 147-grain Silvertip provided the second-best average of the bunch, I’m more inclined to say the gun didn’t like that particular load rather than damn the entire weight class.

One other barrel observation, though, was that the velocity spreads seemed to be greater than typical 1:10-twist barrels. But, on the average, velocities ran very close to advertised values across the board.

Glock Compatibility

Several advertisements and product-information sheets note the STK100’s compatibility with Glock components. On this point, I think the reins should be pulled in — hard. Yes, the STK100 feeds from Glock 17-pattern 17-round magazines, but the one provided was not an OEM unit. Rather it was a Korean-made KCI magazine. I have found KCI mags offered better fit and function than Glock mags in this gun, which were too snug. Also, yes, the front sight is the same, famous post-and-screw arrangement, so Glock sights should fit, too.

Rock Island Armory STK100 Pistol Glock Mags — Patterned to accept Glock 17-style magazines, Armscor ships the STK100 with one KCI polymer mag from Korea.

I would be very cautious about assuming any other Glock components are compatible. Within the slide, for instance, a side-by-side comparison shows the striker assembly components are similar, but not identical. Further, you cannot put a Glock slide on the STK100 frame. I would caution against treating the STK-100 like a Glock. They are not the same gun, and interchangeability is not assured.

Rock Island Armory STK100 Pistol Has Its Own Feel — Though it feeds from Glock mags and has a grip angle akin to a Model 1911, the textured aluminum frame gives the STK100 it’s own feel and balance. The weight reduced felt recoil, too.

Holster Fit

Ideally, every new pistol would launch with full aftermarket support, but that’s not the case. I can’t report on any STK100-specific holsters from popular makers at time of writing.

I was able to circumvent this shortcoming with a “universal” holster option that secures to the mounted light rather than the triggerguard. The Tier 1 Concealed MSP Pro holster was an excellent and comfortable option, especially considering the size and weight of the pistol/light package, and this style of holster is increasingly popular and accessible. I also dumped out my bin of holsters and, looking for close match, found that many (but not all) of my Glock 17 holsters provided good fit and retention with very minor adjustments.

Rock Island Armory STK100 Pistol Holster Options — No holsters were available for testing the STK100, so the author ordered an MSP Pro appendix rig from Tier 1 Concealed that secured to the SureFire X300 light instead of the pistol. It proved comfortable and effective through training. (Mark Fingar photo)

Performance

Final Thoughts

With its first striker-fired pistol, Rock Island Armory has taken a proven operating system and priced it well below the typical cost of an aluminum-framed semiauto. From this experience, the STK100 would be a value at any price.