The esoteric Lewis Machine and Tool Confined Space Weapon 300 (LMT CSW300) is the logical evolution of the many attempts to downsize the M16 rifle for special operations needs. Super compact variants like the Colt Commando date back to the late 1960s, but those had to be padded out to longer overall length with blast-reducing flash hiders to assist in cycling. The end result was a lightweight but marginally effective short barreled 5.56mm rifle used by some Special Forces and, as a survival carbine, by military pilots.

Maximizing Close-Range Effectiveness

The main problem of the Commando was that its ammunition was optimized for much longer rifle barrels. From 10.5-inch tubes, it simply lacked the velocity to make a 55gr bullet sufficiently effective past 100 yards. 7.62x35mm, also known as .300 Blackout, was developed from the start as a cartridge for short barrels, with many loads optimized for sound suppressed use. Whereas 5.56mm tops out at 77 grains, .300 BLK provides 220 grain options at the same velocity. The cartridge works with all the same components, other than the barrel. Compared to the other traditional CQB choice, 9x19mm in HK’s MP5 SD and similar submachine guns, .300 BLK gives both better subsonic performance and the option to run significantly faster supersonic bullets in the 110- to 150-grain range. Built from the ground up as a .300 BLK rifle, LMT CSW300 aimed to make the best of the recent ammunition and sound moderation developments.

LMT CSW300 Features

The core of the weapon is a 1:7 twist, 8.15-inch, chrome-lined barrel with a matched sound suppressor permanently attached for the total length of 11.8 inches. Thanks to that compact configuration, and the specialized reduced length 6-position stock and buffer, LMT CSW300 is only 24.3 inches long with the stock collapsed, 27.6 inches extended. Because it features both a sound suppressor and a barrel shorter than 16 inches even with the suppressor attached, it requires two $200 NFA tax stamps for individuals to own. The barrel and suppressor unit are removable for maintenance. The carbine is hefty for its size, with most of the 7.3-pound weight accruing to the sound suppressor, the barrel and the full-length enveloping forend. The idea behind this configuration was to maximize close-range effectiveness for entry teams, armored vehicle crews and bodyguards.

The LMT CSW300 lower receiver is enhanced with a secondary left-side magazine release. It comes with a very good, crisp two-stage trigger that permits good control even with gloves on. To institutional users, the LMT CSW300 is available in select-fire form with cyclic rates in the 700 to 900 rounds per minute range, depending on the ammunition used. The wide forend protects the sound suppressor from impacts and provides a good standoff from the barrel. At the front of the forend, two downward projections provide indexing for the support hand for maximum direction control without fingers straying before the muzzle. Applying pressure to the very end of the weapon allows precise control both in the aiming and in the recoil control stages of the shot. While the standoff between the suppressor and the forend is smaller there, the can warms up relatively slowly. With gloves on, extended continuous fire is possible before significant discomfort.

The upper receiver features an 18-inch monolithic rail equipped with high quality adjustable folding iron sights and is equally suitable for optics and night vision equipment. The carbine comes with four short rail segments for attaching to threaded holes on the sides of the forend as needed for lights, lasers and other accessories. An ambidextrous charging handle completes the composition.

Test Results

I tested the carbine with the supplied Vortex Razor AMG UH1 holographic sight and with a Primary Arms Gen II 5x Compact Prism scope. With the UH1, the weapon is extremely fast and plenty accurate—this is the real-world use configuration suitable for hitting sporting clays on the 65-yard berm off hand. The magnified optic was used for more deliberate accuracy testing from a support. The three subsonic loads, SIG SAUER and Black Hills 220gr, and Gemtech 187gr, all turned in very respectable 1.5MOA groups. Testing was done at the same 65 yards, with 1-inch spreads for all three. Remington 220gr match grouped less well at 2.5MOA. Aguila 150gr FMJ grouped at 2.25MOA—quite good for a barrel optimized for heavier bullets.

LMT CSW300 has no visible muzzle signature at all, neither flash nor any significant smoke. The rifle also eliminates most of the blowback towards the shooter effectively. The very short direct impingement gas system results in most of the gas and some of the burning powder manifesting at the ejection port. About 40% of the shots made with Remington subsonics and about 15% of the shots taken with SIG SAUER ammunition produced bright, warm fireballs at the ejection port (see photo). That makes the carbine with those rounds uncomfortable by left-handers, ambidextrous controls notwithstanding. While watching videos of other samples of LMT CSW300 in use, I did not see the ejection port flames, but it can be a known issue with short gas systems.

The Good, the Bad and the Dirty

On the plus side, these two loads functioned 100%. I had to go to the LMT engineers about the next issue. Gemtech ammunition did not produce fireballs but short-cycled consistently, ejecting empties without loading the next cartridge into the chamber. Black Hills ammunition, while very accurate, required completely manual cycling, mostly not even unlocking the bolt. This is consistent with chronographed velocities, around 850fps for the SIG and the Remington loads and under 900fps for Black Hills and Gemtech. My best guess was that faster powders used by SIG SAUER and Remington produce both the higher velocity and more of a fireball at the ejection port. The effect appeared at once on a brand new carbine, so it couldn’t have been unburned powder residue. An LMT engineer explained that the wide range of pressure curves between various .300 BLK loads requires tuning the rifle to them—in this case, by taking the anti-bounce weight out of the bolt carrier to enable cycling with the lower port pressure ammunition. Aguila supersonics mostly worked, but by then I ran into another side effect of suppressing such a short weapon: it can run dirty. All the carbon has to go somewhere, so 150 rounds of assorted subsonics were enough to gunk up the gun. Chambering the first round eventually required the use of forward assist, and I had four more failures to go into battery out of 20 rounds. LMT recommends the Hornady and Black Hills ammunition and cleaning every 200 rounds. I did not try just using 200 rounds of Hornady or Black Hills to see if I had the same issue as when all the different rounds were used.

Optimal Defense Weapon

All designs are optimized for certain features, and LMT CSW300 is no exception. Its suppressor does a great job of eliminating gas blowback and stays cool enough for firing about 100 shots in an engagement. The sound reduction is noticeable, but the report—possibly aggravated by the ejection port pop—remains unpleasant to the ear without being immediately damaging. The system is rated 138–139dB with subsonic ammunition. Given the high muzzle pressure inherent in short barrel rifles, this may be physically the best result possible. Ear plugs are recommended even outdoors with subsonic ammunition. In serious use, active hearing protection is worn anyway to attenuate the noise of the opposition’s gunfire. In sum, LMT CSW300 works as an entry or sudden self-defense weapon, provided it is cleaned regularly and compatible ammunition is used.

Some are quick to dismiss the Kel-Tec brand as “utility guns” (as if that is a bad thing). And, admittedly, the Florida-based manufacturer isn’t necessarily focused on perfecting the gleaming, pimped-up look that some shooting enthusiasts fawn over. But it’s a mistake to dismiss the practicality and innovation that founder George Kellgren has worked hard to foster through the years.

For instance, Kel-Tec led the charge of the “mouse gun” back in the early 2000s with the tiny and innovative P-3AT, which was copied ad nauseum by legions of other manufacturers. The company got even more creative with the advent of the KSG, a truly one-of-a-kind shotgun featuring dual magazine tubes that hold 13 3-inch shotgun shells. Then there’s the funky-looking but wildly popular PMR-30. Indeed, if Kel-Tec is guilty of any sin, it’s not being able to keep up with the popularity of Kellgren’s innovative designs (a problem most manufacturers would love to have).

Brother Arms

The company tackled the outdoorsman/survivalist/“prepper” market with the introduction of the SU-16 back in the early 2000s. If you are looking for a durable, dependable and lightweight gun that can be toted through all terrains and conditions, the SU-16 continues to be worth a second look. The gun is chambered for .223 and 5.56 NATO rounds, and if you want a practice version that won’t drain your ammo budget, the SU-22 replicates the design of the 16 while feeding the more affordable .22 LR round. The .22 version is also ideal for beginners or young people who aren’t quite ready for grown-up recoil.

Shooting at 50 yards on an indoor range, the gun is undeniably loud—Kel-Tecs aren’t known for being delicate or quiet; they are rough-and-tumble and in-your-face—but very effective. Maybe a tad more recoil than some AR-style rifles but still perfectly comfortable to use, even for a gal who typically prefers handguns.

Although the gun features a Picatinny rail for a scope or red dot, the aluminum sights were great. We shot two different 16s, one brand new out-of-the-box and the other well-used. One had a peep sight with a standard M16 post and the other featured a peep sight and fiber-optic blade. Both were highly visible, even for a couple of “old folks” with less than 20/20 vision. The sights are fully adjustable: The M16 post can be adjusted by pressing the detent with the tip of a .223 or 5.56 round; while the fiber optic version requires a Phillips screwdriver.

Inspect the Bore

The only real problem I encountered with the SU-16 is a cautionary tale, not for Kel-Tec users but for anyone pulling a new gun out of the package for the first time. On my initial visit to the range, I had three folks lined up to shoot the gun, which had been pulled brand new from its shipping box. Each time we loaded the magazine and grabbed the charging handle, we’d get a misfeed. Each of us, in turn, attempted to load the weapon. We examined the mags, peered into the chamber, made sure the ammo was compatible and even tried an AR mag (the SU-16 is designed to accept standard AR mags, yet another bonus). When that failed, we set the gun aside and shot its little brother, the SU-22.

But I was plagued by the failure. I knew these to be good, durable guns and I hated to go back to Kel-Tec and ask for “one that works.” Several days later, after borrowing a functional model from a friend, I sat down with both guns, hoping to figure out why one worked and the other didn’t. As I peered around the new gun with a small flashlight, the light caught something orange nestled in the bore about an inch from the breech. I looked twice, trying to figure out what I was seeing … yep, it appeared to be orange plastic. Opening the cardboard storage box, I discovered the safety flag with its stem missing! Somehow it had broken off, probably during shipping. I hadn’t noticed the busted flag as I put the gun together, and the stem had been shoved just deep enough into the bore that you had to really work to see that flash of orange. Thankfully, it was close enough to the breech that it prevented us from chambering a round. Had we been able to do so, and then attempted to fire the gun, it might have been a very bad day on the range. To remedy the obstruction, I ran a cleaning rod from the muzzle toward the chamber and the two-inch stem popped out, rendering the gun completely functional.

This is a good reminder to always inspect your bore before putting ammo through it, especially with a brand new gun. I should have known better. I spent more than enough time behind a gun counter listening to newbies whine “it’s broken,” only to discover they had failed to complete some essential step in new gun break-in. Guess this was my comeuppance for all the times I rolled my eyes and pointed out the obvious.

The Firing Line

With both my SU-16s in fine form, and a spare SU-22 for some plinking fun, I spent time on the firing line with retired Sheriff’s Deputy and former academy instructor John Falldorf, a fan of the Kel-Tec brand.

“These guns are durable and designed for a variety of conditions and situations,” he explained. “It’s tough to damage this gun, but, if you do, one of my favorite things about Kel-Tec is their service and repair. Some manufacturers make you wait 6–8 months before they fix your problem. Kel-Tec’s turnaround is extremely good, and they are always eager to make things right.”

He praised the form and function of the SU-16, pointing out that, weighing in at just 5 pounds, the gun is ideal if you are hoofing through the woods. “With a folding stock, that reduces the length to a little over 26 inches; the gun’s designed to shove into a backpack or sling over your shoulder with minimal added weight,” he explained.

Both guns we shot were A models with 18-inch barrels, but the SU is available in several variations, most notably the CA model, with a 16-inch threaded barrel; the C model, also with the threaded barrel and a skeletal folding stock that allows you to shoot from the folded position; and the E model, which has a more standard AR look, including a telescoping stock and a polymer handguard with accessory rail. Previously produced with chrome barrels, Kel-Tec began using salt bath nitride (SBN) on the SUs in 2012, which offers a higher level of corrosion resistance.

Between the two SU-16s, we encountered only one misfeed (in the new model) as we sent rounds downrange into a hostage scenario target. I am happy to say the hostage lived … with nice, neat patterns about an inch across going into the perp’s torso and head. But, like most guns, the SU-16 does, typically, have a break-in period. Fellow shooters have reported periodic misfeeds up to about 150 rounds, when everything smooths out and the gun becomes, as one enthusiast described it, “one of the most reliable rifles I’ve ever owned.”

Functional Features

Deputy Falldorf pointed out the innovative forend, which converts into a bipod, offering the chance to do some prone distance shooting.

The bipod took a couple of tries to master, but once you get the hang of it, it’s ingenious. The two locking tabs are attached to a ring that encircles the barrel. Gently pull down with two fingers and the bipod spreads its wings. To return it to its folded position, simple push forward slightly on the bipod wings as you return them to the barrel, and the locking tabs will snap into place.

From a recoil standpoint, I was pleasantly surprised. The 16 gives you a firm nudge but nothing that left me looking for a shoulder bruise and nothing that impacted my ability to recover for a follow-up shot. With small hands, I felt like I was stretching a bit to get the pad of my finger squarely on the trigger, but I was nonetheless able to depress the 5–7-pound trigger and keep my finger on it as it reset. The mag release button is easy to use, although the polymer/plastic mags don’t always pop out of the mag well without some coaxing; same is true when retrieving them from their storage channel in the stock; a minor inconvenience, at worst. The charging handle on the right also does a nifty job of deflecting flying casings and is attached to the bolt, which moves it back and forth during firing. By accident, we discovered that you can lock the bolt open by depressing a button located at the rear of the mag well.

It was a very simple gun to use and understand, even for someone who is primarily a handgunner.

“The great thing is that it’s consistent with every other AR-15 platform I’ve ever shot,” Falldorf noted. “That’s especially good because, at around $600, it’s much cheaper than many of your ‘high-end’ ARs and just as functional, even more so with the benefit of the folding stock and attached bipod. It’s also cool that you can carry two fully loaded 10-round mags in the stock.”

The SU-16 is also piston-operated, something you usually see in more expensive AR platforms. Unlike the gas impingement versions, piston-operated guns tend to run cooler and cleaner in the chamber. Chalk up another point for the Kel-Tec engineers.

Add an SU-22

Once we finished putting the 16s through their paces, we ran some rounds through the economical SU-22. The feel was very similar and, of course, there was virtually no recoil, courtesy of the soft-shooting .22 LR rounds.

While I tend to think of the .22 AR styles as being more for beginners or kids, Deputy Falldorf sees the value in having one on hand, no matter one’s skill level.

“If you already own an SU-16, then having an SU-22 just makes sense. Ergonomically, it’s pretty much the same, so you can refine your skill with function drills, trigger press and sight alignment practice for a fraction of the ammo price,” he said.

There is no bipod on the SU-22, however.

All in all, my time spent shooting the SU-16 and its little brother confirmed everything I had read and heard about this durable weapon—and everything I already knew about Kel-Tec’s innovative approach to firearms. Best of all, I now have something to add to next year’s Christmas list.