For the past 30-plus years, the name Curtis Higgins and S&H Arms of Oklahoma, Inc., have been at the forefront of quality machine gun conversions of Heckler & Koch (HK) semi-auto rifles and carbines. The business started in 1986 manufacturing thousands of registered HK autosears prior to the May 19, 1986, ban on new machine guns and conversions. Since the 5/19/86 Day of Infamy, Curtis and his company have converted innumerable HK 93, 91 and 94 rifles into fully transferrable select fire versions of the models 33, G3 and MP5 (for more info: curtis@sandharms.com). While several other manufacturers also made the autosears, the S&H conversions were coveted due to the flawless cosmetics and functioning of the weapons. S&H was also known for its autosears for the FNC and, to a lesser extent, autosears for the Ruger 10/22. To this day, S&H is known as the premier gunsmithing facility for HK machine guns.

1986 also was the year S&H entered the suppressor market with MP5 muzzle suppressors, HK MP5SD integral suppressors and a variety of integral rimfire suppressors for Ruger .22LR weapons, the Ruger 77/44 and the Marlin .45 Camp Carbine. Curtis licensed his integral Ruger rimfire designs to John’s Guns.
Small Arms Review recently received S&H’s latest suppressed weapon, an integrally suppressed upper receiver chambered for the popular AAC .300 Blackout cartridge, an improved version of the SSK .300 Whisper originally designed by J.D. Jones.

Designed for a 9-inch barrel, the .300BLK’s popularity has risen dramatically due to the simple conversion of the AR-16/M16 weapons simply by changing the barrel with its associated gas block. Even the M249 belt-fed machine gun is set up for this cartridge. For many purposes, the .300BLK cartridge is ideal: .30 caliber bullet, short barrel, subsonic and supersonic loadings with bullet weights ranging from 110 grains to 220 grains. The loadings using bullets 150 grains or less are supersonic while those with the heavier bullets are generally subsonic.

The S&H Model 30 is a complete assembly consisting of an integrally suppressed upper receiver with an overall length of 28.8 inches and a ported 16-inch, 1:5 barrel. The ports bleed excessive propelling gas into a sealed chamber in the rear of the suppressor.  It weighs 89.7 ounces (5.6 pounds). It utilizes the bolt, charging handle and lower receiver of the user’s AR-15 or M16. For our evaluation, we used a Bushmaster select fire AR-15 lower receiver with a standard buffer intended for 5.56 weapons.

The unit is a conventional direct impingement gas system which mounts easily on an AR-15 or M16 lower receiver using the bolt assembly and charging handle from the host weapon. The handguard has a full-length Picatinny rail and has as standard equipment easy-to-use, flip-up sights. The 1.5-inch-diameter suppressor outer tube extends rearward over the barrel over 15 inches back to the gas block and approximately 5.5 inches forward of the muzzle. The baffle stack in this forward section contains five conventional baffles. The exit hole in the front end cap is configured to use a standard 3/8-inch hex wrench for disassembly. The large chamber surrounding the barrel is fed by four ports in the barrel several inches forward of the gas port. This permits proper usage of this chamber rather than relying on reverse gas flow at the muzzle.

The entire suppressor can be disassembled by the user for cleaning and maintenance. The only tools needed are a 5/32-inch hex wrench for the handguard and a 3/8-inch hex wrench for the front end cap. For total disassembly, a special spanner wrench from S&H is needed to loosen the retaining nut that tightens the suppressor outer tube onto the threaded barrel end. Removal of the baffles and spacers from the front section is somewhat tedious. Unlike firearms with moving parts, suppressors generally perform better if they are not cleaned (with the exception of rimfire suppressors). From the writer’s experience examining suppressor designs, it is estimated that performance degradation will not become apparent for many tens of thousands of rounds, and cleaning is not recommended.

Of major interest to users is the sound performance of the system. Sound measurements were made in compliance with MIL-STD-1474D (Section 5). Two Larson-Davis model 800B sound level meters were used, each with its Larson-Davis model 2530 random incidence ¼-inch instrumentation microphones. These are compliant with rise/response times less than 20 microseconds. Measurements were made at the reference location (one meter left of the muzzle 90º to bore axis, 1.6 meters above grass) and at the simulation of the shooter’s left ear (SLE, 8cm rearward of the receiver, 18cm left of bore axis). By using two sound meters, it is possible to obtain both location readings for each shot. Because MIL-STD permits the use of weighting and because weighting is the industry standard, measurements were made utilizing C-weighting.

Five rounds of 125-grain Black Hills supersonic, five rounds of Gemtech 187-grain subsonic, five rounds of TNQ 220-grain subsonic and five rounds of Remington 220-grain subsonic ammunition were used, and the results averaged. In addition, velocity was measured both at the muzzle and at 25 yards using a Labradar radar chronograph. Velocity at greater range was not possible due to constraints of the range used. Sound levels and velocities are shown in Table 1.

While performing sound testing, several malfunctions were noted with the Gemtech 187gr, the TNQ 220gr and the Remington 220gr subsonic ammunition. The 125gr Black Hills supersonic functioned flawlessly.  Because of malfunctions with the subsonic ammunition, high-speed video was taken, concentrating on the ejection port to document actual bolt travel and rearward bolt velocity. Video tests were performed on a 3-shot burst with the camera operating at 10,000 frames/second. The TNQ 220-grain subsonic was not photographed due to having only enough ammunition to perform sound and velocity measurements. The high-speed video of the bolt opening showed normal rearward travel with the supersonic ammunition but only approximately 66%–75% rearward travel with the subsonic ammunition.  Opening bolt velocity was 3750mm/second with supersonic ammunition and less than 2,000mm/second with subsonic. The subsonic bolt travel was enough to permit case ejection at the 4 o’clock position but not enough to feed the next round from the magazine.

Sound levels with all varieties of ammunition tested were below 140dB at the reference location with the subsonic ammunition showing averages around 130dB. Readings at the shooter’s left ear location were in the upper 140dB region, probably due to some ejection port noise and gas leakage in the region of the gas block. Supersonic readings were somewhat higher than subsonic. The reference location is a good indicator of perception by the target in the far field.

Velocity readings were as anticipated for the ammunition used. All subsonic ammunition had a muzzle velocity just under 1,000 feet/second, and all exhibited a drop of approximately 50 feet/second at 50 yards. The Remington 220gr subsonic exhibited the greatest round-to-round variation in velocity with a standard deviation of around 30. The TNQ 220-grain subsonic showed the least variation.

Quantifying flash requires a light meter capable of holding the intensity of the single brightest light peak. Lacking access to such a meter, there are two methods of evaluating flash: long camera exposure (about 1 second) on a dark night or high-speed video. High-speed video offers the option of performing filming in daylight with a black background for contrast. It also offers the option of looking at bullet stability. With a ruler in the field of view, a reasonable estimation of the intensity can be made. Figure 5 is the single frame showing the greatest amount of flash.

Firearms have little value if they are not accurate. A lead-sled was used as a bench rest, and a target was shot at 50 yards. It was decided to utilize the Black Hills 125gr supersonic ammunition because its greater kinetic energy is most likely to be used for neutralizing targets. The supply of this load was limited without enough to zero accessory optical sights. As a result, the flip-up iron sights on the weapon were used. The front post (.058 inch) is approximately 6MOA wide. The group size is under 3MOA (target grid is one inch).

In all, SAR’s testing of the S&H M30 integrally suppressed upper receiver was very positive. While it is a larger suppressor, it is also very successful for 300BLK suppression and accuracy. Curtis should be proud of his continued success in providing a good product for the end users.

This article first appeared in Small Arms Review V22N9 (November 2018)

Sitting here in relative isolation watching the snow fall, my mind drifts to pondering over two of many gifts from China, the most recent being the novel coronavirus with its social distancing. The other, a number of centuries ago, was gunpowder which permitted engaging targets at relatively great distances with the disadvantage of significantly more noise than that of the bow and arrow. A little over 100 years ago, Hiram Percy Maxim applied some of his automotive muffler concepts to firearms, thereby starting the modern firearm silencer (or, more correctly, suppressor) industry. Initially popular for backyard shooting, silencer technology and interest languished with passage of the original National Firearms Act of 1934. The imposed tax of $200 (over 7 ounces of gold) for a $7 silencer was prohibitive during the Great Depression of the 1930s.

World War II saw military development of silencers primarily for clandestine operations by the British SAS and our OSS. Weapons included the De Lisle carbine, STEN MK IIS, Welrod, OSS High Standard HDM-S Military and a number of other similar designs built experimentally for various platforms. Our involvement in Vietnam spurred development of newer, silenced weapons by small companies (such as Military Armament Corporation and Knight’s Armament) for the military market. In the same time frame, a young entrepreneur with a class 2 Federal Firearms License, Jonathan Arthur Ciener, started modifying mostly Ruger .22LR weapons into silenced versions and advertising widely with small, one-inch-column ads in periodicals aimed at the sportsman, collector and shooter. These ads mostly sold his catalogs, but they did spark interest in the general public.

It was only a few years until the number of civilian-oriented, small manufacturers grew in size and quantity to what we have today, where silencers are pretty much mainstream. The technology has also blossomed over the past half century from dimpled washers in a piece of tube or glass-pack muffler designs to more complex machined baffles, monocores and now 3D-printed exotic designs. Each has its advantages and drawbacks. In a similar vein, user-serviceability has also run a cyclic gamut from the sealed units of Maxim’s suppressor, to user-maintainable in the post-Vietnam era, back to sealed units around the start of the 21^st century, and again back to user-serviceable today (especially in the dirty rimfire calibers).

Prices have increased also. Where Maxim sold his rimfire silencers for $7, today’s rimfire units run in the vicinity of about $200 dollars. His $15 .30-caliber rifle silencers have morphed into today’s retailing in the vicinity of $1,000. However, if one considers the price of gold that rose from $35/ounce to the vicinity of $1,800/ounce (12/1/20), the cost is comparable. The difference is that the tax has not changed since 1934, meaning that instead of the tax being 10 to 20 times the value, it is now about a tenth or fifth the value depending on caliber. And the technology, durability, performance and lifespan have increased significantly.

Today’s consumers have changed also. I have been legitimately involved in the industry for nearly half a century, first as a hobbyist and later as a businessman. In days gone by, the primary concern was sound level. The designs were relatively large and often heavy. Reputation and marketing were primarily spread using word of mouth, print advertisements and reviews published in gun magazines. The design approach was often simplistic and based on WWII experience. The Department of the Army’s Frankford Arsenal Report—Silencers: Principles and Evaluations, Report R-1896 (Leonard W. Skochko and Harry A. Greveris,

 August 1968) was one of the early scientific discussions of silencer technology, and a number of the discussed principles and analyses are still valid today. The report’s early attempts at sound level measurement seriously missed the mark, but at least it was an attempt to quantify the degree of sound reduction. In the 1970s and for many years to follow, the standard instrument for measuring firearm sound levels was the Bruel & Kjaer (B&K) 2209 (with a ¼-inch pressure microphone) to be joined by the Larson Davis 800B in the 1980s. Both measured peak levels reasonably accurately. Today, we have the B&K Pulse system which is probably the most accurate-to-date instrument for measuring the short duration peaks of gunshots.

While initially the emphasis was on quieting the muzzle blast for near-silent shooting, hearing damage issues have assumed greater concern. Many of us older shooters, especially veterans, can trace significant hearing loss due to gunfire. Today’s shooters often have similar hearing loss, but the main etiology has been painful rock concerts and headphones used with the Sony Walkman cassette player and subsequent MP3 music players, not firearms where they have used hearing protectors.

In my opinion, the purpose of a silencer is to decrease the sound level generated by the sudden release of high-pressure propelling gases. So doing makes shooting more fun. Sound decreases according to the inverse square law wherein the pressure drops in a linear manner with each doubling of the distance from the source. Additionally, significant sound is generated by supersonic bullets in flight, but the shock wave is not perceived by the shooter until it reflects off a downrange object. This sound also decreases by the inverse square law, and because it is a reflection, the origin of the sound cannot be determined by an observer. As a result, the ballistic crack is never a source of hearing damage to the shooter. Silencers do an admirable job in concealing the origin of the shot, and in hunting scenarios the target will either be blissfully ignorant of the danger, be simply confused or run toward the hunter.

Do I think silencers should not be regulated? Most definitely. It is a shame that the Hearing Protection Act iterations have failed, but deregulating silencers is not politically correct. Further, it would involve Congress forfeiting a tax source, albeit small.

Today’s silencers are definitely smaller and lighter than the ones from 30 to 40 years ago and are usually more efficient. However, there are limits to the degree of suppression for a given size unit governed by the laws of physics. There are wide choices of manufacturers and models. The majority of promotion today relies on the internet with manufacturers’ websites, digital magazine reviews and discussion forums (which are too often a source of intense misinformation). While military users weigh flash/dust signature, length and weight issues above sound concealment, in the civilian market cosmetics and cool factors seem to be the dominant driving force rather than sound. I have heard more than one silencer marketing director state that he can’t sell round pieces of pipe (regardless of performance) and that new cosmetics are needed every 6 months to remain competitive—kind of like Detroit cars. Exterior-enhancing cosmetic cuts and swirls are too often necessary to sell a proven interior design. Monocores are the current rage, and while many are effective, many are marginal in sound reduction, and virtually all have a significant first-round pop. They do make service simpler (if user disassembly is desired), and they are less expensive to produce, considering parts count and today’s robotic manufacturing machines.

What I have real difficulty in understanding is the love affair with so-called “micro silencers”—tiny, short silencers that don’t appreciably reduce sound levels but that are expensive and command a $200 tax stamp. We have measured several for 5.56 NATO weapons that reduce the sound level by less than 10 db. In my opinion, when one wants something Hollywood-quiet and Hollywood-sized, a suppressor in .22LR is really hard to beat. Most are in the 1×5- or 1×6-inch platforms, fairly inexpensive, have a classic appearance and perform slightly better than Maxim’s suppressor from a century ago. I also have difficulty in understanding the mindset behind investing several cubic dollars plus a tax stamp in a silencer just to see how many rounds it takes to destroy the unit in a machine gun. Guess I am just getting old. Beware of symbolism over substance.

The snow has stopped, and the sun came out. I think I’ll bundle up, go outside in the back yard and hone my skills with my suppressed .22 pistol while shooting pigeons off my roof.

Ruger Silent-SR Series Suppressors

Sturm, Ruger & Co., Inc. is the quintessential example of American capitalism at its best. The company was founded with a meager $50,000 investment by William B. Ruger and Alexander M. Sturm in a small, rented machine shop in Southport, Connecticut in 1949 for the purpose of manufacturing firearms. At that time, there were serious doubts within the industry with insider experts saying that “it can’t be done,” and that the entire industry was in decline. It was assumed that the large established name gun makers would continue to dominate the market.

What the industry didn’t count on was that this new company was guided by a number of innovative concepts, not the least of which was William B. Ruger’s desire to build each product “to a standard so that I would want one even if it was made by our competitors.” These basic principles of innovation, quality and value have earned the company the position of pre-eminence in the firearms industry over the past 68 years. Ruger, which is one of only two firearms manufacturers traded on the New York Stock Exchange, produces millions of firearms each year for hunting, target shooting, collecting, self-defense, law enforcement and government agencies.

Ruger’s first product was the Ruger Standard pistol in .22LR. With some design innovations inspired by the Japanese Nambu and cosmetics/ergonomics of the German Luger, it became wildly popular—it was comfortable to hold and shoot. A retail price in the 1950s of $37.50 (representing fewer than 40 hours minimum wage effort), decent accuracy and good reliability were winning factors. Designed with manufacturing economy in the forefront, it had a 4.75-inch barrel and fixed sights. Many a bullseye match shooter had one in the bottom of his bag to permit finishing a match when his finely tuned target gun malfunctioned. It was also found tossed in the bottom of fishermen’s tackle boxes. Its popularity (and that of the 10 /22 rifle) started an ever growing industry of accessory makers.

Ruger is no stranger to the National Firearms Act weapons, having developed and built several machine guns. In the late 1980s Ruger purchased the rights to the UZI and what became the MP9 from Uziel Gal, its designer. In 1995, Ruger introduced its MP9 9mm submachine gun. Although recognized as an improved UZI, the weapon never became popular or even well known. Bill Ruger held the belief that civilians should not have access to machine guns and established the company policy that no Ruger machine guns would ever be sold to civilians, including Class 3 firearms dealers. The market was to be domestic law enforcement and international military. However, noted in the company’s law enforcement catalog, marketing to law enforcement requires personal demonstrations by local Class 3 firearm dealers. The MP9 was discontinued in 1996. Ruger’s other venture into the machine gun market was a variant of their 1973 Mini-14, the AC-556, which looked exactly like the Mini-14 but had a selector switch (semi, burst, full-auto) at the receiver right rear. The standard AC-556 was offered in both blued and stainless versions as well as a shorter weapon with a folding stock and 13-inch barrel (AC-556K or AC-556F) in blue or stainless. With marginal sales (although far better than the MP9), production was discontinued in 1999 and support terminated 10 years later. Until William B. Ruger’s death in 2002, no Ruger machine guns were sold to civilians. The civilian marketplace was through sale of police trade-ins.

Part of Ruger’s success has been through good market research, outstanding engineering and production of innovative products without significant bureaucratic impediments to slow down development. Part has been financing through reinvestment of profits rather than using traditional debt structure. And part has been by doing manufacturing in-house. Ruger’s Pinetree Casting (Nashua, NH) is one of the foremost investment casting facilities, and in addition to many Ruger weapon receivers, does casting for golf clubs. In 2014, the company purchased Megamet Solid Metals Inc., based in St. Louis, Missouri, to add metal injection molding (MIM) casting capability not only for increased production capacity, but to markedly reduce development time for new products. Unlike many of its competitors, Ruger has not acquired related companies, either competitors or accessory makers.

The use of silencers has become mainstream over the past 4 to 5 years, a fact not overlooked by Ruger. Although their 10 /22 rifles sold in the international market were routinely threaded 1 / 2-20 for European rimfire silencers, it wasn’t until several years ago that domestic Ruger .22 rifles and pistols came threaded 1 /2-28 for the US market. Ruger looked at possible acquisition of a silencer company but after due diligence decided to start building suppressors in-house at their New Hampshire facility.

Approximately a year ago, Ruger introduced two sound suppressors designed for rimfire cartridges: the “Silent-SR” thread mounting muzzle suppressor and the “Silent-SR ISB” integrally suppressed barrel for their take-down 10 /22 rifle.

Both suppressors are attractively packaged in boxes with a fitted foam insert. Any necessary tools are included: a cast composite spanner wrench for removing the endcaps of the Silent-SR and a hex wrench for disassembling the integral Silent-SR ISB. All suppressors are supplied with a 12-page, well written and profusely illustrated manual that covers legal and safety aspects, specifications, attachment to the host weapon, use, disassembly and cleaning instructions. Disassembly for cleaning is simple, and it is virtually impossible to reassemble incorrectly. Both are finished in black Cerakote.

Testing Protocols

The first question posed by most users relates to sound performance since that is the stated goal of a sound suppressor. There are a number of ways to evaluate sound levels, starting perhaps with Mitch WerBell of Sionics fame in the 1970s where he lined up the office staff and shot two different suppressors behind their backs asking which was quieter. While this has merit in distinguishing suppressed from non-suppressed weapons, subtle differences are distorted by the individual hearing damage of different observers.

A more objective method is to use sound measuring equipment that meets the requirements of MIL-STD-1474D. Not all sound meters are capable of accurately measuring the short peaks of firearm sounds, and even some industrial precision meters do not have the necessary peak detector. There are two classic field portable sound meters that meet all the requirements of MIL-STD-1474D: the B&K 2209 and the Larson-Davis 800B with their appropriate ¼-inch pressure microphones. Originally costing in the $5,000 range, both are currently out of production but are frequently available at reasonable cost. Factory service and recertification services are still available. For testing both Ruger suppressors, two of the L-D 800B meters were used, both of which were recertified by Larson-Davis 4 months prior to this test.

MIL-STD calls for a number of measurement locations. For the purposes of the most meaningful and familiar results, sound levels were measured simultaneously at the standard Reference Location (1.6 meters above grass, 1 meter left of the muzzle 90O to bore axis) and at a simulation of the shooter’s left ear (SLE). The Reference Location gives an indication of how the target or down range observer will perceive the gunshot, and the SLE will give one of the better indications as to potential hearing damage. While some advocate using the shooter’s right ear, close contact with a rifle stock confuses weapon action noise with muzzle blast reduction. The simulated SLE positioning of the microphone is 8 centimeters rearward of the back of the receiver (70 centimeters in the case of a handgun) and 18 centimeters left of the bore axis. By measuring both locations simultaneously for each shot, variations in individual rounds are minimized.

For each weapon-suppressor combination, three rounds were fired non-suppressed, and the results averaged. This was followed by a five-round string with the results averaged. It has been found that this number of rounds is statistically significant. For each location, the averages and reduction are noted. In addition, first round pop is calculated by subtracting the average of the last four rounds from the first round. First round pop is caused by a secondary detonation of partially burned powder particles encountering oxygen in the suppressor. MIL-STD permits the use of weighting scales. For a number of years dating back into the 1970s, A-weighting was used. In recent years, a number of manufacturers have changed to C-weighting, which is more accurate for the sound levels encountered with firearms.

Both OSHA and MIL-STD-1474D state that hearing protection is required for short duration peak sound levels greater than 140 dB at the shooter’s ear.

A second item of concern in evaluating a suppressor is whether there is any degradation in accuracy (group size) when the suppressor is mounted. There is often a shift in point of impact which can be corrected by sight adjustment. Rifles were used in a solid rest (Lead Sled) for group size measurements both with and without the suppressor at a range of 40 yards.

For handguns, high speed video was performed looking for excessive yaw or tumbling with the suppressor in place. Frame rate was 5,000 frames/second with a shutter speed of 30 microseconds to provide stop action of the bullet in flight during the first 2 feet of travel. The high-speed camera used was a monochrome Olympus iSpeed FS.

A third concern primarily of military importance is night-time recognition of the shooter’s location from flash or heat signature visualization. Because these suppressors are designed only for rimfire, flash signature was evaluated using high-speed video and only when mounted on the MK-II pistol (generally the worst case scenario).

With either suppressor, it is necessary to utilize standard velocity or subsonic .22LR ammunition to avoid the ballistic crack found with high-velocity ammunition. This crack has been measured with CCI Mini-Mag ammunition at 142 dB 1 meter to the side of the bullet flight path. In the case of .17HMR or .22 Magnum ammunition, the ballistic crack of the supersonic projectile is acceptable, and live targets are confused because the suppressor masks the origin of the shot.

Test Conditions

November 4, 2017, was a bright, sunny fall day in Boise, Idaho. The temperature was a chilly 50F with a relative humidity of 37% and a station pressure of 686 mmHg. Wind gusts were less than 3 miles per hour. The speed of sound calculated to 1,107 feet/second.

The ammunition chosen for testing was CCI Standard Velocity .22LR with the 40 grain bullet. This was chosen because it is commonly available, accurate and remains subsonic in almost any barrel length chambered for .22LR.

The Silent-SR thread-mounting suppressor was tested on two weapons. One was a Ruger MK-2 pistol with a bull barrel shortened to 4.5 inches and mounted in a Ransom Rest. The other was a Ruger 77 /22 with the barrel shortened to 16 inches. The Silent-SR ISB was tested on a Ruger 10 / 22-TD, its normal host weapon.

Silent-SR Thread-Mount Suppressor

The Silent-SR is packaged inside a black ballistic nylon pouch with a convenient belt loop. The suppressor length is 5.4 inches, outside diameter is 1.05 inches, and the weight is 6.4 ounces. It is rated for .22 Magnum and .17HMR in addition to fully automatic .22LR. The length of the threads in the mount is .43 inches, standard for the industry, with a .12-inch thread relief in the mount for safe use with barrels not having a thread relief. The threaded mount is a part of the entrance chamber. There are a total of six baffles (type 17-4 stainless steel), all having a bore aperture of .25 inch. The front end cap functions as a seventh baffle. The rear (blast) baffle is symmetric, and the remaining baffles have significant asymmetry. All baffles have a general conical shape with integral spaces. The tight bore aperture requires barrel threads with a true 90O shoulder for alignment.

Sound measurement levels were obtained on both a Ruger MK-II pistol (4.5-inch barrel) and a Ruger 77 /22?bolt action rifle (16-inch barrel). Both of these weapons are used routinely by the author for rimfire sound measurements. Sound performance was excellent as shown in Table 1 with the absolute sound level at the reference location of 120 dB on the MK-II and 116.7 dB on the 77 /22 rifle.

It is important to remember that there will be day-to-day variations in the sound levels that appear to vary with location, humidity and ambient air temperature. Measurements made in a coastal location do not always correlate with those made in a high desert location such as Boise, Idaho. As a rule, five-round strings are statistically valid (standard deviation <1.5), which is why the tables include the standard deviation for the five suppressed measurements. The one exception was measurement at the reference location where the 8 dB first round pop increased the standard deviation. However, calculating excluding the first round resulted in an average of 118.4 dB and a standard deviation of 1.1, which is in line with all other measurements.

Although what is normally asked is the reduction, the more important measurement is the absolute sound level, both for far field and for hearing risk evaluation. First round pop can be eliminated with either an inert atmosphere (nitrogen, carbon dioxide, etc.) or a tiny amount of oil or grease in the entrance chamber. Absolute sound levels for the rifle are considerably lower than for the pistol, but the degree of reduction is significantly less. This is simply because the non-suppressed level on the rifle is significantly lower than on the pistol.

Accuracy and bullet stability were checked differently on the two weapons. With the Silent-SR mounted on the 77 / 22 bolt action rifle, a target was shot with and without the suppressor at a range of 40 yards. Adding the suppressor moved the point of impact down .176 inches (.421 MOA) but tightened the group from .795 inches (1.9 MOA) to .688 inches (1.64 MOA) with three shots touching. See Target 1.

A check of bullet stability on the MK-II pistol was considered difficult lacking optical sights. Instead, a high-speed video (5,000 frames/second) was performed. Lighting was difficult lacking bright sunlight, so two compromises were accepted: 1) a shutter speed of 30 microseconds (instead of the preferable 2 microseconds and 2) image enhancement (which decreased resolution). Eleven consecutive frames showed the bullet in the first 24 inches forward from the end of the suppressor. These 11 photos were superimposed to show the progress of the bullet traversing this distance as shown in the photo. Starting at the 20-inch region, there is slight yaw, which is normal as the bullet transitions from rotating about its physical center to rotating about its center of gravity. There was no visible flash detected.

The manufacturer’s suggested list price for the Ruger Silent-SR thread mounting suppressor (model 19000) is $449.

Silent-SR ISB for the Takedown 10/ 22-TD

The Silent-SR ISB is a complete replacement barrel with integral suppressor assembly for the Ruger 10 / 22-TD rifle. Unlike similar offerings, the Ruger suppressor includes all hardware and the forend composite handguard. The suppressed barrel is 16.12 inches long, making it .5 inch shorter than the standard barrel, and weighs 41.9 ounces as contrasted to the 30.7 ounces of the standard barrel. The suppressed barrel bears a resemblance to the over/under double-barreled shotgun with a width of .925 inches and height of 1.52 inches. The bore aperture throughout the baffle stack is .280 inch.

The suppressed barrel is alloy steel and 10.62 inches long. The aluminum suppressor outer housing has been permanently attached to this barrel to make the overall length in compliance with BATF regulations. The front end cap and baffle stack are easily removed by loosening the assembly bolt, a process well described in the manual. The blast baffle is symmetric, and the remaining six are significantly asymmetrical. All are type 17-4 stainless steel.

Sound measurements were made using the same host 10 / 22-TD receiver and comparing the original non-suppressed barrel with the Silent-SR ICP integrally suppressed barrel. The results are shown in Table 2. The suppressed barrel measured an impressive 114.7 dB at the reference location, which is only approximately 4 dB louder than the hammer falling on a spent cartridge case.

Accuracy testing was performed in the same manner as for the thread mounting suppressor on the rifle. The range was 40 yards, and the weapon was shot using the Lead Sled rest. A fixed 10x scope was attached to the Weaver base supplied with the rifle. Five shot groups were fired with both the standard and suppressed barrels. The target is shown in Target 2. The suppressed barrel tightened the group from 2.9 inches (6.92 MOA) to 2.05 inches (4.9 MOA) and dropped the group center by .77 inches (1.84 MOA).

The group sizes, both suppressed and non-suppressed, were considerably larger than with the thread-mounted suppressor on the 77 /22. There are several reasons for this, not the least of which is a re-worked 2.5-pound honed trigger on the 77 /22 with no over-travel as compared to a rough 6-pound trigger on the 10 /22-TD with significant over-travel.

The second issue is with barrel lockup on take-down weapons. The 10 / 22-TD tensioning ring has to be adjusted when one barrel is replaced with another. The tension at lockup is not totally consistent, and there is the potential for almost imperceptible flex at the barrel/receiver joint. Even simple removal and replacement of the same barrel can cause a minor point of impact shift. The most accurate way to mount an optic on a take-down rifle is to mount it on the barrel rather than the receiver. In contrast, the 77 /22 barrel is mounted in a far more rigid manner using a V-block and torqued mounting screws.

The manufacturer’s suggested list price for the Ruger 10 /22-TD Silent-SR integral suppressed barrel (model 19001) is $629.

Comments

Both suppressors have their strong points, including excellent sound performance, tightening of the shot groups and obvious quality. The Silent-SR ISB for the 10 /22 Takedown is definitely the more compact weapon due to the requirement for a 16-inch minimum barrel length. What would be a worthwhile improvement to the integral Silent-SR ISB would be to supply a rail contoured to the .920 diameter of the steel portion of the barrel for barrel mounting of an optical sight. The thread mounting Silent-SR has the advantage of a wide variety of weapon platforms and the strength to hold up to multiple rimfire cartridges. While both are outstanding, the author has a bias for thread mounting suppressors because of their versatility.

SureFire LLC
RYDER 9-MP5

The stainless-steel-constructed RYDER 9-MP5 is a duty-use suppressor for the H&K MP5 sub-machine gun. The suppressor attaches to a standard three lug barrel via our patented Fast-Attach mechanism, similar to the way our best-in-class SOCOM Series suppressors attach. The suppressor is easily disassembled for cleaning, and the baffles are indexed and numbered for ease of reassembly. Designed for duty use, the RYDER 9-MP5 does not affect bullet performance or increase point of impact/point of aim as is the case with other sub-machine gun suppressors. When it comes to durability, performance, and ease of maintenance, the RYDER 9-MP5 is the clear choice for suppressing the MP5. www.surefire.com

SF RYDER 9-MP5
Caliber: 9mm
Length: 8in (20.3cm)
Weight: 15.6 oz (442g)
Diameter: 1.30in (3.3cm)
Material: Stainless steel
Finish: Cerakote
MSRP: $849

SRT Arms
SRT Integral M-16 / 9MM Uppers

Integrally suppressed 9MM AR15/M16. Integral suppressed upper, 9MM or .45 ACP., 1.5” OD tube. Pinned and welded 16” bolt face to end of tube, or removable for registered MG or SBR lowers. Ported barrel for additional sound reduction.Porting available to make 115 gr subsonic, or max velocity for use with 147gr subsonic. www.srtarms.com

Weight: Adds 1 lb to upper weight.
4130 tube, 7075 AL baffles and end caps.
Finish: Black Cerakote finish.
Absolute db at muzzle is 116-119 db depending on bullet weight.
MSRP: $780 using customer supplied barrel, handguard and upper receiver.

B&T AG
M.A.R.S. QD

Based on combat experience in Iraq, Afghanistan, B&T has analyzed evolving needs of operators and has evolved its products to perfectly serve the new needs. The new M.A.R.S. QD (Miniature Assault Rifle Suppressor–Quick Detachable) offers greater flash reduction, lighter weight and smaller size. For those who prefer the option to be able to mount/dismount the suppressor even during an operation, the M.A.R.S. QD is the perfect choice. It is the lightest quickest detachable mounting system on the market today. www.bt-ag.ch

Caliber: 5.56mm (.223) or 7.62mm (.308)
Length: 161mm (5.56mm) / 192mm (7.62mm)
Diameter: 39mm
Weight: 415 g (5.56) / 480 g (7.62)
Factory-Tested Sound Reduction: 26 dB (5.56)
Materials Inconel/Thermax Finish: sandblasted/grey
MSRP (USD): tba

B&T AG
M.A.R.S. DM

The M.A.R.S. DM (directly mounted) is the lightest and shortest assault rifle suppressor B&T produces. It´s screwed directly on the muzzle. This lack of any mounting system allows it to be almost 300 grams lighter and 50mm shorter than other suppressors with a mounting system. Therefore the impact on the balance of the weapon and the extension of the gun is negligible and not perceptible in combat. Despite its small size the M.A.R.S. is a full gown up suppressors when it comes to muzzle flash and sound reduction. www.bt-ag.ch

Caliber: 5.56mm (.223) or 7.62mm (.308)
Length: 126mm (5.56mm) / 142mm (7.62mm)
Diameter: 39mm
Weight: 380 g (5.56) / 450 g (7.62)
Factory-Tested Sound Reduction: 20 dB (5.56)
Materials: Inconel/Thermax
Finish: sandblasted/grey
MSRP (USD): tba

SRT ARMS
Integrally Suppressed 9mm AR-15/M16

Integrally suppressed upper, 9mm or .45 ACP, 1.5-inch OD tube. Pinned and welded 16-inch bolt face to end of tube or removable for registered MG or SBR lowers. Ported barrel for additional sound reduction. Porting available to make 115gr subsonic or max velocity for use with 147gr subsonic. www.srtarms.com

Caliber: 9mm
Weight: Adds 1lb to upper weight
Diameter: 1.5in
Material: 4130 tube, 7075 AL baffles and end caps
Finish: Black Cerakote
Factory-Tested Sound Reduction: 116-119 dB depending on bullet weight
MSRP: $780 using customer supplied barrel, handguard and upper receiver

ELITE IRON
DELTA MOD2

The Elite Iron DELTA MOD2 is a shorter version of the popular DELTA and is designed for .223 /5.56 rifles only. The compact design and lighter weight makes it a great choice for hunting and tactical applications. Baffle core design minimizes the POI shift. Thread pitch ½ -28. Full-auto rated. www.EliteIron.com

Caliber: .223 /5.56 only
Overall Length: 6.375in
Exterior Diameter: 1.5in
Weight: 17.9oz
Sound Pressure Level Reduction: 35 dB
Materials: Tube is made from 316 SS. Internals are machined from 17-4 H900 SS
Finish: Black Cerakote
MSRP (USD): $720

ELITE IRON
ECHO LITE 5”

The all titanium ECHO LITE 5-inch suppressor is primarily designed for use on handguns and can be used on rifles as well. It delivers solid performance in a lighter suppressor. The ECHO LITE 5-inch can be disassembled for cleaning. Includes takedown tool. Thread pitch 1/2-28 x .400. www.EliteIron.com

ECHO LITE 5”
Caliber: .22 LR only
Length: 5in
Weight: 4.7oz
Diameter: 1in
Material: Titanium
Finish: Black Cerakote
Sound Pressure Level Reduction: 31 dB High Velocity, 35 dB Subsonic
MSRP: $455

LIBERTY SUPPRESSORS
The Sovereign

The Sovereign rifle silencer is perfect for the law enforcement officer, hunter as well as the long-range shooter. It combines lightweight with numerous mounting solutions to create the most versatile and lightweight silencer to date. Titanium construction provides superior strength as well as low muzzle weight for less fatigue in the field. Combined with our LS1 muzzle brake mount, this is the ultimate package. www.libertycans.net

Caliber: 7.62mm
Overall Length: 7in
Exterior Diameter: 1.625in
Weight: 12.5oz
Sound Pressure Level Reduction: 33+ dB
Materials: Titanium/Stainless Steel
Finish: Black Cerakote Type C
MSRP (USD): $1,050

DAKOTA SILENCER
Varminter 4.0

Varminter 4.0 will be available early 2018. The Varminter is a 100% titanium hybrid that’s modular from 9 inches to 7 inches. It’s a hybrid because the 2-inch extension is a uniquely designed monocore baffle system while the 7 inch is all stacked baffles. The Varminter is completely serviceable and comes all the way apart for easy cleaning. Only the Varminter 4.0 .30 calibur will be modular, but Dakota Silencer will also be releasing the Varminter 4.0 in a .223. This will be the quietest Varminter the company has made to date. www.dakotasilencer.com

VARMINTER 4.0
Caliber: .30 and .223
Length: 7in; 9in with extension
Weight: N/A
Diameter: N/A
Material: Titanium
Finish: N/A
Sound Pressure Level Reduction: N/A
MSRP: N/A

THOMPSON MACHINE
The Poseidon 9mm

In production since 2009, the Poseidon 9mm is the smallest, lightest, hearing-safe 9mm suppressor on the market. Its excellent performance on .22LR hosts, .32acp hosts, and .380acp hosts gives it the versatility to match. The Poseidon is in use with military and law enforcement. www.thompsonmachine.net

POSEIDON 9MM
Caliber: 9mm
Length: 4.125in
Weight: 4oz
Diameter: 1.25in
Material: Hard anodized 6061 and 316 Stainless
Design: Monocore, Take-Apart Design
Suppression: Up to 25dB when wet and wiped
MSRP: N/A

About the Author

Dr. Philip Dater has been involved in the sound suppressor industry for over 40 years as Automatic Weapons Company (New Mexico) and Antares Technologies, Inc. His interest has been in the field of design, testing and manufacturing. He founded Gemtech in 1993 and retired in the summer of 2017 at the age of 80. He continues to consult and perform testing on a part-time basis, and several times each year teaches his signature course “Silencer History, Technology & Testing” at Phoenix Defence in Henderson, NV. www.phoenixdefence.com