SSS.6.111 - Maxim Defense DSX SURG 5.56x45mm Short Barrel Automatic AR15 Rifle

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Maxim Defense DSX SURG 5.56x45mm AR15 with 10.3-in Barrel

The DSX is designed and manufactured by Maxim Defense. It is a 5.56mm centerfire rifle silencer, intended to suppress the 5.56x45mm cartridge on barrels as short as 5.5 inches in length. The DSX-D (the direct thread model tested) has a 1.75-inch primary diameter and is 7.9 inches in length from distal wrench features to the base of the direct thread mount. The DSX-M is identical to the DSX-D other than the capability for its direct thread mount to be removed and fitted with universal so-called HUB mounting solutions. Without the direct thread mount installed, the DSX-M is 7.25 inches long. The silencer’s core is monolithic 17-4 stainless steel, and the unit is user serviceable; a retention spring is included that helps to prevent unintended system disassembly during use. The mount, as well as the tube, are Grade 5 titanium. The DSX-D silencer weighs 22.2 ounces, as tested. The DSX-M, without its direct thread mount installed, weighs 20.5 ounces. The DSX silencers may be obtained from Maxim Defense.

PEW Science is an independent private testing laboratory and also the world’s only publicly funded suppressed small arms research cooperative. Testing, data analysis, and reporting is generated with funding provided by PEW Science members. Any test data that is generated with any portion of private funding contains this disclosure. The testing and data production for this Sound Signature Review was funded in part by PEW Science Project PEW-Maxim-049-001-22. Therefore, data pertaining to the DSX SURG in this Sound Signature Review is published with the express written permission of Maxim Defense Industries, LLC.

This publication examines the performance of the Maxim Defense DSX silencer installed on the Maxim Defense Suppressed Upper Receiver Group (SURG) system. A comparison with the MK18 is given below:

  • The SURG system tested possesses the same 10.3 inch barrel length as the standard PEW Science MK18 test host weapon system described in Public Research Supplement 6.51.

  • The same lower receiver weapon assembly was used in testing.

  • The MK18 possesses a 0.070” gas port orifice in the barrel with an oversized gas block orifice.

  • The Maxim Defense SURG possesses a 0.080” gas port orifice in the barrel with a 0.053” gas block orifice.

This Sound Signature Review contains single-test results using the Maxim Defense DSX SURG Automatic AR15 rifle, chambered in 5.56x45mm NATO with a 10.3-inch barrel. Federal XM193 55gr ammunition was used in the test.

  • Section 6.111.1 contains the DSX SURG test results and analysis.

  • Section 6.111.2 contains Suppression Rating comparisons of the DSX SURG and the DSX with dedicated 223 and 30 caliber silencers on the current market on the MK18, including the Thunder Beast Dominus, KAC 5.56 QDC, CGS SCI-SIX, Dead Air Nomad-30, YHM Turbo T2, Dead Air Sandman-S, HUXWRX FLOW 556k, Energetic Armament ARX, KAC QDSS-NT4, Rugged Razor556, Otter Creek Labs Polonium and Polonium-K, Surefire SOCOM556-RC2, HUXWRX HX-QD 556 and HX-QD 556k, Q Trash Panda, CGS Helios QD, SilencerCo Saker 556, Rugged Razor762, and others.

  • Section 6.111.3 contains a detailed holistic signature comparison case study, featuring the DSX on the MK18 weapon system and the SURG (Members Only).

  • Section 6.111.4 contains the review summary and PEW Science subjective opinions.

System Note: The Maxim Defense DSX has also been evaluated on the standard PEW Science MK18 test host weapon system described in Public Research Supplement 6.51. That data and analysis is presented in Review 6.110.

Summary: When incorporated into the Maxim Defense 10.3-in barrel SURG system and fired with Federal XM193, the Maxim Defense DSX achieved a composite Suppression Rating™ of 39.8 in PEW Science testing

When paired with the 10.3-in barrel MK18 and fired with Federal XM193, the Maxim Defense DSX achieved a composite Suppression Rating™ of 38.8 in PEW Science testing (Review 6.110).

As with all weapon systems, the user is encouraged to examine both muzzle and ear Suppression Ratings.

Relative Suppression Rating Performance is Summarized in SSS.7 - PEW Science Rankings

6.111.1 Maxim Defense DSX SURG Sound Signature Test Results

A summary of the principal Silencer Sound Standard performance metrics of the DSX SURG is shown in Table 1. The data acquired 1.0 m (39.4 in) left of the muzzle is available for viewing to all. This is a members-only review and includes pressure and impulse waveforms measured at the shooter’s ear. PEW Science thanks you for your support; further testing, research, and development of PEW-SOFT and the Silencer Sound Standard is made possible by members like you!

 

Table 1. Maxim Defense DSX SURG Sound Metric Summary

 

6.111.1.1 SOUND SIGNATURES AT THE MUZZLE

Real sound pressure histories from a 6-shot test acquired with PEW-SOFT™ are shown below. Six cartridges were loaded into the magazine, the fire control group positioned to single-shot, and the weapon was fired until the magazine was empty and the bolt locked back on the follower of the empty magazine. Only five shots are considered in the analysis. The signatures of Shot 6 are displayed in the data presentation but are not included in the analysis to maintain consistency with the overall PEW Science dataset and bolt-closing signatures. The waveforms are not averaged, decimated, or filtered. The data acquisition rate used in all PEW Science testing is 1.0 MS/s (1 MHz). The peaks, shape, and time phasing (when the peaks occur in relation to absolute time and to each other) of these raw waveforms are the most accurate of any firearm silencer testing publicly available. PEW-SOFT data is acquired by PEW Science independent testing; the industry leader in silencer sound research. For more information, please consult the Silencer Sound Standard.

The primary sound signature pressure histories for all 6 shots with the DSX SURG are shown in Figure 1a. The sound signatures of Shot 1 and Shot 2 are shown in Figure 1b, in early time. The real sound impulse (momentum transfer potential) histories from the same 6-shot test are shown in Figure 2a. In Figure 2b, a shorter timescale is shown comparing the impulse of Shot 1 to that of Shot 2 and Shot 3.

Fig 1a. Maxim Defense DSX SURG 5.56x45mm NATO Automatic Rifle Muzzle Sound Pressure Signature

Fig 1b. Maxim Defense DSX SURG 5.56x45mm NATO Automatic Rifle Sound Pressure Signature

Figure 2a. Maxim Defense DSX SURG 5.56x45mm NATO Automatic Rifle Muzzle Sound Impulse Signature

Figure 2b. Maxim Defense DSX SURG 5.56x45mm NATO Automatic Rifle Muzzle Sound Impulse Signature

Author Note: The behavior at the muzzle of the DSX implemented as part of the SURG system is largely unchanged from that in Review 6.110 in which the DSX was evaluated on the standard MK18 weapon system. The below text has been edited as appropriate, to delineate differing system behavior, particularly at the shooter’s ear. The Member Version of this article is significantly updated due to all Member articles containing in-depth shooter’s ear data and analysis, and in the case of this article, an in-depth signature comparison of the DSX with the MK18 and SURG.

The Maxim Defense DSX exhibits a relatively low gross flow rate, despite its relatively large volume. The sound suppression performance at the muzzle, in the free field, is significant. Consistent initial jetting is noted followed by gradual amplitude increase to eventual peak (Fig 1b). Note the rate of positive phase impulse accumulation in Fig 2a is relatively low. These signature features are indicative of silencers that restrict flow and that may exhibit significant signature suppression, depending upon frequency and phase components. In the case of the DSX, it exhibits the highest Suppression Rating at the muzzle on the MK18 published in the current dataset; slightly higher than that of the Otter Creek Labs Polonium (6.75). It should be noted that the DSX is larger than the Polonium.

PEW Science Research Note 1: The first-round-pop (FRP) from the DSX is noted in both pressure space (Figure 1) and impulse space (Figure 2). It is interesting to note that the FRP is postulated to be extremely minimal to bystanders, relative to subsequent shots, in accordance with PEW Science inner ear modeling. The consistency of the impulse accumulation histories in Fig 2a are also notable, post-FRP.

PEW Science Research Note 2: One of the reasons for the high degree of consistency noted in the signatures is the silencer’s dedicated bore aperture for the cartridge. The Maxim Defense DSX was designed around the M855 5.56x45mm cartridge. Larger bores are still able to produce consistent signatures, but it is more challenging, depending on the technology implemented in the silencer. An example of this challenge displayed in test data and analysis can be seen in test reports featuring silencers such as the Rugged Razor762 (6.58), the Energetic Armament ARX (6.82); the Rugged Razor556 (6.76); the Q Trash Panda (6.61), and the Dead Air Sandman-S (6.92); all display erratic behavior. Less erratic flow rate, despite an even larger over-bore, is possessed by silencers with alternate flow geometry, like the CGS Helios QD (6.66). This silencer is also significantly over-bored, but possesses coaxial flow paths that may be accessed early in its core geometry.

Typically, as a rifle silencer’s bore becomes smaller, flow rate decreases, all other things equal. However, the flow may be somewhat restricted overall, depending on baffle geometry.

PEW Science Research Note 3: The DSX suppresses overpressure amplitude significantly in early time, and although it possesses a relatively low gross overall flow rate, it jets gas extremely consistently not only from shot to shot, but during each shot. The jetting in each shot is relatively smooth over the time window (ref. Fig 2b). Despite the significantly prolonged positive phase, the gross signature severity is lower than typical for its measured free field peak overpressure and impulse. This is most likely a function of overall amplitude and consistency, resulting from generous interior expansion volumes in the monolithic core, coupled with dedicated bore aperture. This behavior results in a signature, on the MK18, that is less severe at the muzzle and relatively less severe to the operator when compared to silencers with similar gross flow rates. Muzzle signature contributes significantly to operator hazard level, regardless of weapon system. In the case of the DSX performance on the SURG system, dividends are gained with reduction in ejection port signature. That phenomenon is explored in Section 6.111.1.2 and Section 6.111.3.

PEW Science Research Note 4: As in all semiautomatic AR15 weapon testing, a second pressure pulse originates from the ejection-port signature of the weapon and it occurs early enough in time such that its waves coalesce with that of the muzzle signature. However, in late time (at approximately 100 ms in Figure 1a) the mechanical noise of the bolt closing is observed. The pressure signature of Shot 6 does not display this event due to the bolt remaining open after the sixth and final round is fired from the magazine. Note the significantly later time at which the bolt closing signatures occur with the DSX SURG system, compared to with the DSX on the MK18. This is driven by gas port size.

The shape, timing, and magnitudes of the early-time pressure pulses and overall shape of the impulse waveforms measured at the muzzle, from shot-to-shot, are relatively consistent. The consistency of the waveform amplitudes highlight the silencer’s overall sound performance consistency at the muzzle after the FRP, as well as the relative consistency of the tested automatic rifle firearm configuration.

As typically indicated, first-round sound signatures always differ from subsequent shots, as the atmosphere within the silencer changes. The FRP phenomenon cannot always be shown by viewing only the peak sound pressure. This is one of the reasons why The Silencer Sound Standard requires examining multiple sound signature metrics. Ammunition consistency can play a role in the determination of FRP, however, the close examination of measured pressure and impulse waveforms typically excludes ammunition from the possible factors influencing true FRP, due to the relative consistency of most high quality factory ammunition.

PEW Science Research Note 5: Note that the muzzle Suppression Rating of the Maxim Defense DSX SURG is 38.5 and the at-ear Suppression Rating is 32.5; the same zone on the Suppression Rating Dose Chart. The influence of the lower flow rate (higher back pressure) of the Maxim Defense DSX on the weapon dynamics is offset by the smaller gas port size in the SURG system, resulting in delayed system unlocking, allowing for chamber pressure to drop further prior to the chamber being exposed to atmosphere, resulting in less of a pressure differential and facilitating a less severe ejection port signature. This decreases the hazard to the weapon operator when compared to using the same silencer on the standard MK18 weapon system, as was demonstrated in Review 6.110. The signatures measured at the shooter’s ear are presented below.

6.111.1.2 SOUND SIGNATURES AT SHOOTER’S EAR

Real sound pressure histories from the same 6-shot test acquired with PEW-SOFT at the shooter’s ear are shown below. Again, the waveforms are not averaged, decimated, or filtered. The data acquisition rate used in all PEW Science testing is 1.0 MS/s (1 MHz).

The primary sound signature pressure histories at the ear for all 6 shots are shown in Figure 3. The primary sound signature history is shown in Figure 3a. A zoomed-in timescale is displayed in Figure 3b, in the region of peak sound pressure for Shots 1, 2, and 3. The real sound impulse (momentum transfer potential) histories at the ear from the same 5-shot test are shown in Figure 4. Again, full and short timescales are shown.

Figure 3a. Maxim Defense DSX SURG 5.56x45mm NATO Automatic Rifle Ear Sound Pressure Signature

Figure 3b. Maxim Defense DSX SURG 5.56x45mm NATO Automatic Rifle Ear Sound Pressure Signature, Short Time Window

Figure 4a. Maxim Defense DSX SURG 5.56x45mm NATO Automatic Rifle Ear Sound Impulse Signature

Figure 4b. Maxim Defense DSX SURG 5.56x45mm NATO Automatic Rifle Ear Sound Impulse Signature Peaks

The waveforms measured at the shooter’s ear in Figure 3 and Figure 4 are significantly different than those measured when using the same silencer on the MK18 weapon system. This is driven purely by effective gas port orifice size and its influence on weapon dynamics.

The plot scales have been kept constant between the MK18 test report and this test report to illustrate the difference in signatures. Note the gross pressure amplitudes are significantly lower, with the same further delayed bolt closing signatures (Figure 3a, 98 ms) that were previously noted in the measured free field muzzle signatures, above.

PEW Science Research Note 6: Another significant difference in these measured signatures, when compared to those measured from the same silencer with the MK18, is the impulse timing. This offers crucial insight into AR-15 weapon behavior, as it pertains to sound signature at the operator’s location. There is a waveform feature in Figure 4 pertinent to the behavior of silencers on the standard MK18 that differs with the SURG. Note that the FRP impulse waveform typically diverges from the rest of the shots, post-peak, in any MK18 test in which the FRP is measurable at the shooter’s ear and the ejection port signature exhibits abnormal coalescence. Only in cases of extremely high flow rate does FRP accumulate to its maximum, pre-peak (become front-loaded). Front-loaded impulse is noted with the DSX SURG in Figure 4b, above.

This is because FRP is largely a muzzle signature phenomenon. That is, the components of the signature measured at all locations, associated with FRP, originate from the endcap orifice of the silencer. With a standard MK18 (untuned; 0.070” gas port, H2 buffer, carbine buffer spring), silencer flow restriction usually results in the FRP contribution in the shooter’s ear impulse signatures occurring post-peak; the ejection port signature dominates the signature in earlier time, accumulating impulse faster. Serendipitously, the Maxim Defense SURG system with the DSX possesses the same 10.3 inch barrel length with the only difference being the effective gas port orifice size. The influence of the lower flow rate (higher back pressure) of the Maxim Defense DSX on the weapon dynamics is offset by the smaller gas port size in the SURG system, resulting in delayed system unlocking, allowing for chamber pressure to drop further prior to the chamber being exposed to atmosphere, resulting in less of a pressure differential and facilitating a less severe ejection port signature. This results in impulse accumulating slower. Because the impulse at the shooter’s ear is less dominated by the ejection port signature, FRP accumulation is front-loaded. The signature from the muzzle now controls this part of the signature.

Author Note: This is the first time such a comparison, with this level of data fidelity and pedigree, has been published in the history of small arms. PEW Science thanks you for your support. Your membership is directly responsible for this research being possible.

The above factor directly illustrates the benefit of “tuning” an AR-15 weapon system for a silencer. As the only primary variable changed is the effective gas port size, the ejection port signature contribution to the total signature is reduced. This DSX SURG signature data is compared with DSX MK18 data for members in Section 6.111.3 of this article.

PEW Science Research Note 7: Note that just as with the MK18, the FRP differential at the shooter’s ear with the DSX is not as minimal as at the muzzle. This should be expected, given that the FRP phenomenon is a muzzle-originating phenomenon and should not change with ejection port gas dynamics. The overall severity of FRP to the shooter is lower with the SURG than with the MK18, but the relative severity is comparable. Even though FRP signature contribution is muzzle-driven, holistic signature at the operator’s location is driven by both pressure origins.

6.111.2 Suppression Rating Comparison (5.56x45mm from the MK18 and SURG)

Figure 6 again presents a comparison of the PEW Science Suppression Rating of the Maxim Defense DSX to that of other rifle silences on the MK18 automatic AR15 rifle. The standard PEW Science MK18 test host weapon system is described in Public Research Supplement 6.51. Figure 6 does not show a SURG comparison.

Figure 6. Suppression Rating Comparisons of the Maxim Defense DSX and other silencers on the MK18, Using PEW-SOFT 5.56x45mm Supersonic Test Data and PEW Science Analysis

Author Note: The below text is largely unchanged from that in Review 6.110 in which the DSX was evaluated on the standard MK18 weapon system. It is included due to the relevance of the gross silencer behavior. It has been edited as appropriate, to delineate differing system behavior, particularly at the shooter’s ear. The Member Version of this article is significantly updated due to all Member articles containing in-depth shooter’s ear data and analysis, and in the case of this article, an in-depth signature comparison of the DSX with the MK18 and SURG.

Figure 6 presents the detailed PEW Science Suppression Ratings, computed at the muzzle and ear, for the listed silencers on the MK18. The Suppression Rating is a holistic parameter that captures human inner ear damage risk potential from a measured impulsive overpressure signature. The parameter may be used with the dose chart at the beginning of this report.

When examining the relative performance of the silencers presented above, the Maxim Defense DSX is shown to posses a less severe muzzle signature than all of the other silencers shown in the current dataset, on the standard MK18 weapon system. The DSX’s Suppression Rating to bystanders is similar to that of the Otter Creek Labs Polonium (6.75). This degree of muzzle suppression on the standard MK18 is significant; for the Suppression Rating to approach the so-called 40-zone from a 10.3 inch barrel 5.56x45mm weapon system is notable. To illustrate the relative severity of the signatures of dedicated 5.56x45mm silencers like the DSX, there also exist dedicated 5.56 silencers that produce significantly more severe muzzle signatures. Such silencers include the Energetic Armament ARX (6.82); a silencer with a signature on the MK18 that may be considered hazardous to bystanders, even for relatively low dose exposure, compared to that from the Maxim Defense DSX. The suppressed MK18 weapon system can produce significantly different hazards to personnel, depending on the silencer used.

PEW Science Research Note 8: It is interesting to note that despite the high degree of muzzle suppression, the Maxim Defense DSX exhibits a Suppression Rating at the shooter’s ear on par with that of the Surefire SOCOM556-RC2 (6.52), on the MK18. This is due to flow rate; although the DSX possesses more overall gross flow restriction, it also suppresses more at the muzzle. The flow restriction does induce a greater ejection port signature contribution, dropping the level of protection at the shooter’s ear on the MK18, but not severely compared to most dedicated-bore 5.56 silencers.

The Maxim Defense DSX, evaluated with the Maxim Defense Suppressed Upper Receiver Group (SURG), represents a system fielded by end users requiring an optimized upper receiver system paired with a silencer. The evaluated SURG system is different than the standard MK18, despite having the same barrel length. A high level comparison of DSX MK18 and DSX SURG performance is provided in Figure 7, below. It is not appropriate to compare SURG behavior of a silencer to MK18 behavior of other silencers; the comparison is skewed due to the host weapons being different. The comparison in Figure 7 is provided only because the identical silencer is used on both systems; the silencer is not the variable.

Figure 7. Suppression Rating Comparisons of the Maxim Defense DSX on the MK18 and SURG, Using PEW-SOFT 5.56x45mm Supersonic Test Data and PEW Science Analysis

As shown in Figure 7, the Suppression Rating at the shooter’s ear may be significantly influenced by the ejection port signature from the MK18; all other things equal. This publication directly illustrates the benefit of “tuning” an AR-15 weapon system for a silencer. It is important to note that not all silencers will possess the same increase in shooter’s ear Suppression Rating from weapon tuning. Signature at the operator’s head is a function of both muzzle and ejection port signatures from the AR-15 weapon system. In-depth signature comparisons with the DSX on the SURG and MK18 weapon systems are provided below.

6.111.3 Signature Comparison Case Study - Maxim Defense DSX MK18 and SURG 5.56x45mm NATO Automatic Rifle

Section 6.111.1.2 of this article presents significant conclusions obtained from the comparison of the holistic signatures measured at the operator’s location. This section presents both free field muzzle impulse and shooter’s ear impulse, for both SURG and MK18 systems, for Shot 1 and Shot 2. The waveform timescales have not been shifted; and slight time phasing differential at the start of impulse accumulation should not be construed to indicate different dynamics; the triggering differential of data acquisition may differ between tests. Thus, the differential is inconsequential for this analysis. A comparison of the gross waveform behavior and timing in the below figures is pertinent. Waveforms measure 1.0 m left of the end cap, in the free field, are presented in Figure 8.

Figure 8a. Maxim Defense DSX MK18 and SURG 5.56x45mm NATO Automatic Rifle Muzzle Sound Impulse Signature Comparison (Shot 1)

Figure 8b. Maxim Defense DSX MK18 and SURG 5.56x45mm NATO Automatic Rifle Muzzle Sound Impulse Signature Comparison (Shot 2)

Note the behavior at the muzzle is largely unchanged. However, there is a difference in impulse decay noted during FRP; Figure 8a displays a stall in rarefaction at approximately 31.5 ms from the MK18, whereas the impulse decay from the SURG system is shown to be more linear. However, during Shot 2, it is the DSX that stalls at that same time. The cause of this behavior is the subject of future PEW Science research; it is postulated it is related to chamber dwell differences between the two systems (not to be confused with gas port dwell time differences, which are identical in this case) and possibly latent time ejection port signature coalescence. Of further technical note, it is likely that the chamber dimensions of the Daniel Defense MK18 and the Maxim Defense SURG are different, which may further change gas dynamics in an unpredictable way. Impulse waveforms measured at the shooter’s ear are presented in Figure 9.

Figure 9a. Maxim Defense DSX MK18 and SURG 5.56x45mm NATO Automatic Rifle Ear Sound Impulse Signature Comparison (Shot 1)

Figure 9b. Maxim Defense DSX MK18 and SURG 5.56x45mm NATO Automatic Rifle Ear Sound Impulse Signature Comparison (Shot 1)

The comparisons in Figure 9 form the most significant differentials in this article. There is a nuance in the timing comparison with the waveforms in the above two figures which is different than that discussed previously in Section 6.111.1.2.

As discussed previously, MK18 shooter’s ear FRP impulse waveforms are almost always back-loaded compared to subsequent shots because the contribution to the signature at the shooter’s ear is typically dominated in early time by ejection port signature, as FRP is a muzzle-driven phenomenon. It takes time for the FRP signature from the muzzle to coalesce with the ejection port signature at the shooter’s head. However, if you compare MK18 shooter’s ear impulse waveforms to SURG shooter’s ear impulse waveforms, the MK18 waveforms will be front-loaded relative to the SURG waveforms, regardless if they are from the first shot or the final shot (ref. Fig 9a and Fig 9b). This is because every shot to the shooter, with a SURG system, is less dominated by ejection port signature. The untuned suppressed MK18 will always force impulse to accumulate at the shooter’s ear faster than will a tuned suppressed host, unless the silencer exhibits an extremely high flow rate (HUXWRX, etc).

6.111.4 Review Summary: Maxim Defense DSX SURG 5.56x45mm AR15 with 10.3-in Barrel

When incorporated into the Maxim Defense 10.3-in barrel SURG system and fired with Federal XM193, the Maxim Defense DSX achieved a composite Suppression Rating™ of 39.8 in PEW Science testing. When paired with the 10.3-in barrel MK18 and fired with Federal XM193, the Maxim Defense DSX achieved a composite Suppression Rating™ of 38.8 in PEW Science testing (Review 6.110). As with all weapon systems, the user is encouraged to examine both muzzle and ear Suppression Ratings.

PEW Science Subjective Opinion:

The Maxim Defense DSX is a full-size 5.56 machine gun rated rifle silencer. With a manufacturer-rated barrel length minimum of 5.5 inches for fully automatic firing schedules, the DSX is appropriate for extreme duty use. The signature suppression performance of the silencer incorporated into the SURG exhibits the highest holistic suppression performance on a 10.3-in system tested by PEW Science, to date. Note that the DSX has also been evaluated by PEW Science on the standard MK18.

Suppressed Upper Receiver Group (SURG) systems are often fielded by end users requiring an optimized upper receiver system paired with a silencer. The following notes apply to the DSX testing and analysis with the MK18 and SURG:

The SURG system tested possesses the same 10.3 inch barrel length as the standard PEW Science MK18 test host weapon system described in Public Research Supplement 6.51.

The same lower receiver weapon assembly was used in testing.

The MK18 possesses a 0.070” gas port orifice in the barrel with an oversized gas block orifice.

The Maxim Defense SURG possesses a 0.080” gas port orifice in the barrel with a 0.053” gas block orifice.

Use of a SURG system, compared with an untuned MK18 system, may significantly reduce hazard to the weapon operator. The degree of hazard reduction is both system and silencer dependent and is not uniform for all systems or silencers.

The Maxim DSX possesses an asymmetrical monolithic steel core. Such silencer internal geometries are colloquially referred to as “monocores.” Monocore silencer design is mature in the modern silencer market and has existed for decades. Advantages of monolithic cores include simplified manufacturing, system alignment, and in the case of the DSX, generous expansion volumes for the 5.56x45mm cartridge, resulting in significant muzzle signature suppression.

Despite its large volume, the DSX is not a “low backpressure” silencer. Just as mature as monocore designs, is the antiquated (and incorrect) assertion that silencer backpressure is a function of internal volume. Silencer backpressure is a function of shock propagation and gross flow rate. The DSX possesses significant overall flow restriction, as evidenced in the measured waveforms, weapon kinematics, and ejection port signature contribution to shooter hazard on the standard MK18 weapon system. This phenomenon is further illustrated in the significantly improved performance of the DSX at the shooter’s ear when using the tuned SURG system in lieu of the standard 0.070” gas port MK18 upper assembly.

The DSX possesses some relatively unique features for a duty-use 5.56 silencer. For example, it is user serviceable; the steel monocore can be removed from the titanium tube for maintenance. There exists a steel retention spring that helps to prevent unintended system disassembly during use. If the user does not wish to field the silencer in the direct thread configuration, the DSX-M model exists in which the direct thread insert can be removed and the user’s choice of so-called “HUB” mounting systems can be installed.

The performance of the Maxim Defense DSX, for the size, is not necessarily an outlier in the overall state of practice. However, it is the first example of a monocore design published in The Silencer Sound Standard analysis pedigree, to date. The fact that it also happens to exhibit significant 5.56x45mm SBR suppression performance is also notable. Also notable is that the DSX is rated to pass multiple SOCOM SURGE firing cycles, on barrels as short as 5 inches.

In this review, the DSX performance metrics depend upon suppressing a supersonic centerfire rifle cartridge on a short barrel gas-operated rifle, which is an incredibly difficult task. PEW Science encourages the reader to remain vigilant with regard to all supersonic centerfire rifle suppression claims. The gas volume and combustion products created by the firing of the supersonic 5.56x45mm cartridge are significant; the measured pressure and impulse magnitudes, and their durations, illustrate this fact. Silencer performance on automatic (reciprocating) rifles depends on many factors. Weapon configuration may significantly influence total suppressed small arm system performance.

The hearing damage potential of supersonic centerfire rifle use is significant. PEW Science encourages the reader to consider the Suppression Rating when deciding on an appropriate silencer and host weapon combination for their desired use.