SSS.6.226 - Rampart Range Suppression Carson 556 and the MK18 5.56x45mm Short Barrel Automatic AR15 Rifle (Free Version)

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Rampart Range Suppression Carson 556 on the MK18 5.56x45mm AR15 with 10.3-in Barrel

The Carson is designed and distributed by Rampart Range Suppression.  It is designated the "Carson 556” in this report to differentiate it from the previously evaluated Carson 30.  It is a .223 caliber centerfire rifle silencer, intended to suppress the 5.56x45mm cartridge with semiautomatic or fully automatic fire. The Carson 556 has a 1.71-inch diameter and is 6.59 inches long with no mount. The silencer may be attached to a variety of weapon systems depending on the user’s choice of mount; the tested third-party 3/4-24tpi direct-thread mount increased the system length to 7 inches.  Other mounting options are possible due to the rear of the silencer body being HUB compatible (1.375-24 tpi threading). The core of the Carson 556 is a 3D printed titanium Otter Creek Labs Infinity derivative and the end cap is non-removable.  The silencer weighs 9.7 ounces and the tested direct thread mount weighs 1.2 ounces, for a total system weight of 10.9 ounces, as tested. The Carson 556 can be obtained from Rampart Range Suppression and Capitol Armory.

Silencer Hazard Map:

The predicted personnel hazards generated by the tested weapon system in this report, in the free field, are shown in the adjacent Silencer Hazard Map. Click or tap the Map to enlarge.  Please reference Silencer Hazard Map Brief 8.1.23 for further details.  The PEW-SOFT HD Blast Hazard Prediction Tool and Hazard Mapper is presented in Report 8.1.1.

Rampart Range Carson 556 10.3-in MK18 AR-15 Free Field Hazard Map Produced by PEW-SOFT HD Blast Hazard Prediction Tool using PEW Science Test Data

PEW Science is an independent private testing laboratory and also hosts the world’s only independent public 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 analysis production for this Sound Signature Review was funded in part by PEW Science Project PEW-RAMP-138-25. Therefore, data pertaining to the Carson 556 in this Sound Signature Review is published with the express written permission of Rampart Range Suppression.

The testing and analysis presented in this Sound Signature Review are of the Carson 556 direct-thread mounted on the MK18 Automatic AR15 rifle rifle, chambered in 5.56x45mm NATO with a 10.3-inch barrel. Federal XM193 55gr ammunition was used in the test. The standard PEW Science MK18 test host weapon system is described in Public Research Supplement 6.51.

Report Table of Contents:

  • Section 6.226.1 contains Rampart Range Carson 556 test results and analysis.

  • Section 6.226.2 contains overall Suppression Rating performance comparisons of the Rampart Range Carson 556 with other silencers on the current market on the standard untuned MK18 automatic rifle.

  • Section 6.226.3 contains an article summary and PEW Science laboratory staff opinions.

Summary: When paired with the 10.3-in barrel MK18 and fired with Federal XM193, the Rampart Range Carson 556 mounted with a direct-thread mount achieved a composite Suppression Rating™ of 42.5 in PEW Science testing.

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.

6.226.1 Rampart Range Carson 556 Sound Signature Test Results

A summary of the principal Silencer Sound Standard performance metrics of the Rampart Range Carson 556 is shown in Table 1. The data acquired 1.0 m (39.4 in) left of the muzzle is available for viewing to all. The data acquired 0.15 m (6 in) right of the shooter’s ear is only available to membership supporters of PEW Science and the Silencer Sound Standard. You can support public PEW Science testing, research, and development with a membership, here. State-of-the-art public firearm sound signature testing and research conducted by PEW Science is supported by readers like you.

 

Table 1. Rampart Range Carson 556 Sound Metric Summary

 

6.226.1.1 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 public dataset and bolt-closing signatures. The waveforms are not averaged, decimated, or filtered. The data acquisition rate used in all PEW Science laboratory sound signature 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 laboratory testing; the recognized 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 Rampart Range Carson 556 are shown in Figure 2a. The sound signatures of Shot 1 and Shot 2 are shown in Figure 12b, in early time. The real sound impulse (momentum transfer potential) histories from the same 6-shot test are shown in Figure 3a. In Figure 3b, a shorter timescale is shown comparing the impulse of Shot 1 to that of Shots 2 and 3.

Fig 2a. Rampart Range Carson 556 5.56x45mm NATO MK18 Automatic Rifle Muzzle Sound Pressure Signature

Fig 2b. Rampart Range Carson 556 5.56x45mm NATO MK18 Automatic Rifle Sound Pressure Signature

Figure 3a. Rampart Range Carson 556 5.56x45mm NATO MK18 Automatic Rifle Muzzle Sound Impulse Signature

Figure 3b. Rampart Range Carson 556 5.56x45mm NATO MK18 Automatic Rifle Muzzle Sound Impulse Signature

Like the previously evaluated Carson 30 (6.216), the Rampart Range Suppression Carson 556 is a titanium rifle silencer that uses a modified Otter Creek Labs Infinity inner core, under license.  Therefore, the Carson 556 is classified as a hybrid design, incorporating both high flow rate features and conventional geometries to control distal blast propagation while reducing adverse influence on weapon function. Like the Infinity 762 silencer, the Carson 556 is specifically classified as a staged hybrid in the PEW Science Silencer Sound Standard research taxonomy.  For an overview of the three primary classes of rifle silencer designs, the reader is encouraged to review PEW Science Research Supplement 6.169.  Several other staged hybrids have been evaluated by the PEW Science Laboratory and comprehensive performance Rankings are provided in Section 7 of the Standard.  MK18 performance comparisons are provided in Section 6.226.2 of this report. 

PEW Science Research Note 1:  The Carson 556 is a very high performance dedicated 5.56 rifle silencer and is, for all intents and purposes, is a Carson 30 with a dedicated 5.56mm appropriate end cap aperture. The baffle core bore size of the silencer is the same as the Carson 30.  Therefore, the Carson 556 is very similar in gross design to an Otter Creek Labs Infinity 762 with 5.56 solid end cap installed (6.179). However, there are distinct differences between the Carson series and the Infinity series:

  1. The Carson 556 is constructed from 3D-printed titanium, whereas the Infinity 762 is 3D-printed Inconel.

  2. The Carson 556 has a non-removable solid end cap assembly with different internal and external aperture geometries than those present in the Infinity’s removable solid end cap. 

  3. The proximal core sections of both silencers are similar; however, the distal geometry and termination of annular flow differs in the Carson 556.  The first expansion (blast) chamber vent structure also differs.

As was the case withe the Carson 30, the geometric changes in (2) and (3) result in slightly elevated performance, for both operators and bystanders, when using the Carson 556 versus the Infinity 762 on the on the MK18. The Carson 556 appears to be slightly more optimized for the MK18 platform, though the performance difference between the two silencers is minimal. Note that the Carson 556 is approximately half the weight of the Infinity, which may be a significant practical difference for some users.

PEW Science Research Note 2:  Further comparing the Carson 556 to the Infinity with its solid 5.56 end cap, the peak blast overpressure an impulse values produced by its signature are lower across the entire risk field than with the Infinity. The overall blast momentum propagation behavior, however, is largely the same in a gross sense. The following are observations from the above Carson 556 blast data:

  1. Initial precursor and internal combustion signature components are more pronounced from the Carson 556 than from the Infinity; this is most likely due to the titanium construction vs. the Inconel construction of the Infinity (Fig. 2b, early time).

  2. Initial coupled jetting from the Carson 556 is higher amplitude, which may be a result of the end cap geometry changes in the last expansion chamber (Fig. 2b).

  3. Momentum ramp is somewhat delayed; the onset of blast impulse accumulation is pushed somewhat forward in time, and this momentum ramp appears to slightly increase blowdown time and momentum control (Figure 3).

  4. Combustion propagation stabilizes in Shot 3, just as it did in the Infinity test. This is likely an inherent Infinity core attribute (Fig. 3b).

Performance observation (1) validates the expected physics, but is largely unremarkable with regard to practical performance implications. Observation (2) is also of little consequence, particularly when it is considered in combination with observations (3) and (4), which highlight why the Carson 556 slightly outperforms the Infinity on this host weapon.

PEW Science Research Note 3: FRP control with the Carson 556 on the MK18 is robust. There is less early-time divergence than with the Infinity, which also has strong FRP suppression performance on the MK18. The Infinity core, in general, is not a high performer in FRP suppression across all host weapons and combustion regimes, but short barrel 5.56mm NATO appears to pose less of a challenge for this technology, particularly in the Carson 556 configuration. It is likely that the design differences highlighted in Research Note 1, item (3) result in these FRP suppression performance gains.

PEW Science Research Note 4: At the time of writing, the measured performance of the Rampart Range Carson 556 places it in the Top 5 in the overall MK18 PEW Science Rankings, slightly below the PTR VENT 3 (6.135).  However, it should be noted that the Carson 556 has higher back pressure than the VENT 3, and that is reflected in the shooter’s ear Ratings of the two silencers; ejection port blast severity on the standard untuned host is somewhat more severe with the Carson 556. To put this in further context, the Carson 556 doesn’t quite reach the Top 25 of the MK18 Rankings in shooter’s ear Suppression Rating, again, on an untuned host weapon.  These performance distinctions are extremely important to understand, particularly considering total silencer system length, performance implications when weapons are tuned, etc.  For further context regarding both performance and size balance, the reader is encouraged to use the Suppression Rating Parametric Visualization Tool (Members Only) for independent study.

PEW Science Research Note 5:  It is extremely important for the reader to understand the Suppression Ratings are computed with free field test data, and are therefore universal when translating the weapon and operator to different environments without reflections.  However, when the environment becomes complex with many reflecting surfaces, performance translation of different systems is not yet possible; sound field shapes and particle velocities result in varied blast wave time-of-arrivals, as well as changes of blast load angles of incidence; these variations change amplitude and phase waveform components.  As a result of these inevitable environmental complexities, user impressions will vary, as both the shooter and bystander.  Nonetheless, hazard reduction efficacy in the free field, as characterized by the Suppression Rating, holds.  The Suppression Rating comparisons are the current state-of-the-art, and the most “apples to apples” sound suppression performance comparisons that currently exist.  Further research is ongoing. The reader should note that shooting a Carson 556 indoors and a HUXWRX FLOW silencer indoors may result in different blast overpressure risk profiles.  Despite the HUXWRX silencer(s) have a higher free field shooter’s ear Suppression Rating, it is likely that shooting near walls and obstacles will be more hazardous with a FLOW silencer.

PEW Science Research Note 6: As in all semiautomatic AR-15 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 95 ms in Figure 2a) 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.

PEW Science Research Note 7: The closing time of the AR-15 bolt is directly related to the flow restriction of a silencer for a given weapon system. PEW Science has determined bolt closing time variation from the unsuppressed state to be a reliable indicator of silencer back pressure, with strong correlation with the PEW Science Back Pressure Metric, Omega and the alpha parameter. However, PEW Science has also determined that the indicator is unreliable upon upper receiver fouling. Sound signatures are not influenced by this fouling, as these kinematics occur in late time, after gas venting to atmosphere. Momentum transfer, weapon condition (upper receiver fouling), and other factors, can significantly influence bolt closing time. PEW Science urges the reader to exercise extreme caution if using the published bolt closing time to make determinations regarding silencer flow restriction (back pressure) or weapon system kinematics. This type of calculation may provide erroneous results, as the weapon condition at the time of each test is not published data. The time-scale duration showing bolt closing time is only published by PEW Science such that the signature data pedigree may be verified.

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 8:   Note that the muzzle Suppression Rating of the Rampart Range Carson 556 is 42.4 and the at-ear Suppression Rating is 23.8; different zones on the Suppression Rating Dose Chart. The high early time flow rate (low back pressure) of the Carson 556 does contribute to a less severe ejection port blast signature than several other silencers, but the back pressure is not low enough to substantially reduce ejection port blast loads to the shooter on the standard MK18 weapon system without tuning.  The reader is encouraged to examine the Silencer Hazard Map at the top of this report as detailed in Silencer Hazard Map Brief 8.1.23.  Weapon tuning will influence hazard reduction efficacy, and is outside the scope of this study.

The signatures measured at the shooter’s ear with the Carson 556 are presented and analyzed in the full Member Version of this report.

Overall performance comparisons follow.  Note that as a PEW Science Member, you have access to a very powerful comparison tool in the Rankings, which can filter for length and weight.

6.226.2 Suppression Rating Comparison (5.56x45mm from the MK18)

Figure 6 presents a comparison of the PEW Science Suppression Rating of the Rampart Range Carson 556 with that of several other silencers on the MK18 weapon system. The standard PEW Science MK18 test host weapon system is described in Public Research Supplement 6.51.  Note that for more comparisons, the reader may view the comprehensive filterable and sortable table in the Rankings Section of the Standard. The below table is sorted by total system length, as tested. Lengths are listed in every silencer test report, and filterable in the Member Rankings Section tool.

Figure 6. Suppression Rating Comparisons of rifle silencers in Order of Length Using PEW-SOFT 5.56x45mm Supersonic MK18 Test Data and PEW Science Analysis

Figure 6 presents an overall summary of the postulated hazards to the operator and bystanders when fielding a variety of different short silencers on the standard MK18 weapon system.  The Rampart Range Carson 556 from this test program is shown in red.  Hazards are expressed with the Suppression Rating; a holistic parameter that captures human inner ear damage risk potential from a measured impulsive complex blast overpressure signature during the entire time regime of weapon operation, including combustion, complete blowdown, and all mechanical operation, including the carrier group returning to battery, in the true free field. The parameter may be used with the dose chart and Hazard Map at the beginning of this report.  The PEW Science Suppression Rating is a damage risk criterion (DRC), a lower Suppression Rating indicates a higher personnel hazard in the free field - it is not a subjective quantity; it is an objective quantification of hearing damage risk potential.  Due to its true free field test data origin and complete waveform analytical calculation basis, it is the only known universal suppressed weapon system signature comparison metric available.  Analytically computed metrics are color-coded in the Rankings Table, in all Silencer Hazard Maps, and keyed to the dose chart for user interpretation.

The following gross conclusions can be made from the metrics presented above:

PEW Science Research Note 11:  Without weapon system tuning, operator hazards from a suppressed MK18, in the free field, plateau at Suppression Ratings near 30.  This is due to ejection port blast loads.  However, this does not mean that silencers with similar shooter’s ear Suppression Ratings will sound the same to the shooter, in the free field. On the contrary, what an operator hears through the entire time regime of a gun shot event and subsequent environmental reflections, and which acute hazards manifest, may be different.  The reader is strongly encouraged to review the published Silencer Hazard Map at the top of this report and in Silencer Hazard Map Brief 8.1.23.  Furthermore, to illustrate two extremes, the difference in spatial hazards from a Flow Through silencer and a high back pressure silencer are directly compared in Silencer Hazard Map Brief 8.1.5 (HUXWRX FLOW 556k vs. SilencerCo Saker 556).

As stated in Research Note 4, At the time of writing, the measured performance of the Rampart Range Carson 556 places it in the Top 5 in the overall MK18 PEW Science Rankings, slightly below the PTR VENT 3 (6.135).  However, it should be noted that the Carson 556 has higher back pressure than the VENT 3, and that is reflected in the shooter’s ear Ratings of the two silencers; ejection port blast severity on the standard untuned host is somewhat more severe with the Carson 556. To put this in further context, the Carson 556 doesn’t quite reach the Top 25 of the MK18 Rankings in shooter’s ear Suppression Rating, again, on an untuned host weapon.  These performance distinctions are extremely important to understand, particularly considering total silencer system length, performance implications when weapons are tuned, etc.  For further context regarding both performance and size balance, the reader is encouraged to use the Suppression Rating Parametric Visualization Tool (Members Only) for independent study.

Hybrid designs continue to demonstrate significant performance with supersonic ammunition suppression, and silencers like the Rampart Range Suppression Carson series, and others, show that performance can be achieved in compact design envelopes. The overall balanced performance of these next generation systems are significantly elevated when compared to that of highly prolific previous generation hybrids such as the Surefire SOCOM556-RC2 (6.52) and other newly released military silencer hybrids such as the KAC PRT family (6.156) on this weapon system. Users now have additional high performance practical options to reduce weapon system length and maintain hazard reduction.

As detailed in this report, signature at the operator’s head is a function of both muzzle and ejection port signatures from the AR-15 weapon system.  Specific weapon system parameters will dictate hazard reduction efficacy. 

Small arm weapon system suppression performance is a spectrum. The PEW Science Suppression Rating and the Silencer Sound Standard help quantify this spectrum for end users and industry, objectively.

6.226.3 Review Summary: Rampart Range Carson 556 on the MK18 5.56x45mm AR15 with 10.3-in Barrel

When paired with the 10.3-in barrel MK18 and fired with Federal XM193, the Rampart Range Carson 556 mounted with a direct-thread mount achieved a composite Suppression Rating™ of 42.5 in PEW Science testing.

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

PEW Science Laboratory Staff Opinion:

The Rampart Range Suppression Carson 556 is a full size titanium 5.56 rifle silencer with highly competitive muzzle suppression and a flow rate conducive to effective use on the semiautomatic rifles.  The 3D printed titanium modified Infinity core of the Carson 556 is lighter weight than typical and is intended for field duty use; not heavy continuous strings of fully automatic fire. The 11 ounce system is optimized for semiautomatic AR-15 platforms and the rear is HUB mount system compatible.

Like the previously evaluated Carson 30, the Rampart Range Suppression Carson 556 is a titanium rifle silencer that uses a modified Otter Creek Labs Infinity inner core, under license.  Therefore, the Carson 556 is classified as a hybrid design, incorporating both high flow rate features and conventional geometries to control distal blast propagation while reducing adverse influence on weapon function. Like the Infinity 762 silencer, the Carson 556 is specifically classified as a staged hybrid in the PEW Science Silencer Sound Standard research taxonomy. 

First-round-pop (FRP) control with the Carson 556 on the MK18 is robust. There is less early-time divergence than with the Infinity, which also has strong FRP suppression performance on the MK18. The Infinity core, in general, is not a high performer in FRP suppression across all host weapons and combustion regimes, but short barrel 5.56mm NATO appears to pose less of a challenge for this technology, particularly in the Carson 556 configuration. It is likely that the design differences in the first and last expansion chambers result in these FRP suppression performance gains.

At the time of writing, the measured performance of the Rampart Range Carson 556 places it in the Top 5 in the overall MK18 PEW Science Rankings, slightly below the PTR VENT 3.  However, it should be noted that the Carson 556 has higher back pressure than the VENT 3, and that is reflected in the shooter’s ear Ratings of the two silencers; ejection port blast severity on the standard untuned host is somewhat more severe with the Carson 556. To put this in further context, the Carson 556 doesn’t quite reach the Top 25 of the MK18 Rankings in shooter’s ear Suppression Rating, again, on an untuned host weapon.  These performance distinctions are extremely important to understand, particularly considering total silencer system length, performance implications when weapons are tuned, etc.  For further context regarding both performance and size balance, the reader is encouraged to use the Suppression Rating Parametric Visualization Tool (Members Only) for independent study.

Despite its titanium construction, it is likely that the durability of the Carson 556 is higher than some other titanium silencers on 5.56 NATO weapons due to its internal geometry. The end user is encouraged to contact Rampart Range Suppression for further guidance.

The Carson 556 is HUB mount capable. The user may adapt the silencer to a variety of mounting systems of their preference. The silencer is 6.59 inches long without a mount. The tested direct-thread mount increased system length to 7 inches.  It is likely that performance of the Carson 556 would not appreciably change with a shorter direct-thread mount.

In this review, the Rampart Range Suppression Carson 556 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.