SSS.6.98 - YHM Turbo T2 and the MK18 5.56x45mm Short Barrel Automatic AR15 Rifle
/YHM Turbo T2 on the MK18 5.56x45mm AR15 with 10.3-in Barrel
The Turbo T2 is designed and manufactured by Yankee Hill Machine Co (YHM). It is a 223 caliber centerfire rifle silencer, intended to suppress the 5.56x45mm NATO cartridge. It has a 1.56-inch diameter and is 5.5 inches in length, without a mount. The total length with the included YHM Phantom Q.D. adapter and muzzle brake is 6.9 inches. The user may choose to install third-party adapters compatible with the 1.375”-24tpi system. The silencer is tubeless; the entirety of the welded assembly is constructed of heat treated 17-4 stainless steel, with the exception of the blast baffle that is constructed of an Inconel steel alloy. As tested, the silencer weighs 10.4 ounces and the Phantom Q.D. mount assembly weighs weighs 6.7 ounces, for a total system weight of 17.1 ounces. The Turbo T2 can be obtained from Silencer Shop.
This Sound Signature Review contains single-test results using the YHM Turbo T2 with its included Phantom Q.D. muzzle brake mount on the MK18 Automatic AR15 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.
Section 6.98.1 contains the Turbo T2 test results and analysis.
Section 6.98.2 contains Suppression Rating comparisons of the Turbo T2 with dedicated 223 and 30 caliber silencers on the current market, including the 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 6.98.3 contains the review summary and PEW Science subjective opinions.
Summary: When paired with the 10.3-in barrel MK18 and fired with Federal XM193, the YHM Turbo T2 mounted with the muzzle brake mount achieved a composite Suppression Rating™ of 29.8 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
6.98.1 YHM Turbo T2 Sound Signature Test Results
A summary of the principal Silencer Sound Standard performance metrics of the YHM Turbo T2 tested with the muzzle brake mount 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. YHM Turbo T2 Sound Metric Summary
6.98.1.1 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 Turbo T2 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 Shots 1 through 3.
Fig 1a. YHM Turbo T2 5.56x45mm NATO MK18 Automatic Rifle Muzzle Sound Pressure Signature
Fig 1b. YHM Turbo T2 5.56x45mm NATO MK18 Automatic Rifle Sound Pressure Signature
Figure 2a. YHM Turbo T2 5.56x45mm NATO MK18 Automatic Rifle Muzzle Sound Impulse Signature
Figure 2b. YHM Turbo T2 5.56x45mm NATO MK18 Automatic Rifle Muzzle Sound Impulse Signature
The YHM Turbo T2 is an updated version of the legacy YHM Turbo silencer that includes “universal” rear mount adaptability as described in the opening paragraph of this article, as well as enhanced flash hiding features on its distal orifice. The Turbo T2 possesses three primary baffles and a fourth perforated Inconel steel blast baffle. The perforated blast baffle provides additional expansion volume for 5.56x45mm jetting in early time, while also shielding the primary baffles in the stack from direct blast jet impingement.
The YHM Turbo T2 is a dedicated bore 5.56x45mm rifle silencer, much like the Surefire SOCOM556-RC2 (Review 6.52) and the SilencerCo Saker 556 (Review 6.53). Typically, silencers intended for dedicated use with the 5.56x45mm cartridge restrict gas flow to a greater degree than those with a larger bore; the ancillary baffle stack venting in the SOCOM556-RC2 notwithstanding. Even with a marginally larger bore sized for .243 (6mm) projectiles, gas flow may be significantly restricted, depending on holistic internal silencer design. This has been demonstrated in the analysis of performance of silencers such as the Otter Creek Labs Polonium (Review 6.75), which is capable of suppressing 6mm cartridges, but still exhibits significant flow restriction on the MK18 5.56x45 AR15 weapon system.
The flow restriction (back pressure generation) of the Turbo T2 is significant. The early-time muzzle pressure signatures shown in Figure 1b demonstrate this with relatively prolonged peak pressure generation and significantly decoupled bullet shock from initial jetting. This phenomenon is also highlighted in Figure 2a, in which the rate of rise to peak positive phase impulse is relatively slow. The measured impulse accumulation behavior of the YHM Turbo T2 is similar to that of both the SilencerCo Saker and Otter Creek Labs Polonium; all three silencers significantly restrict gas flow on this host weapon platform.
First-round-pop (FRP) does occur with the YHM Turbo T2, in both pressure and impulse space (Figure 1 and Figure 2, respectively). However, the FRP in the muzzle signature from the Turbo T2 is not predicted to induce adverse hearing damage risk to bystanders, when compared to that of subsequent shots, in accordance with PEW Science inner ear response analyses. This lack of significant FRP is notable for the suppressed MK18 weapon system. Despite this advantage, the YHM Turbo T2 does exhibit increased signature severity throughout the shot string. This phenomenon is a subject of future PEW Science research.
PEW Science Research Note 1: 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 75 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.
PEW Science Research Note 2: The closing time of the MK18 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. 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, until the aforementioned late-time irregularities resulting from primary axial over-bore.
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 3: Note that the muzzle Suppression Rating of the YHM Turbo T2 with the muzzle brake mount is 28.8 and the shooter’s-ear Suppression Rating is 21.0; the same zone on the Suppression Rating Dose Chart. The lower flow rate (higher back pressure) of the YHM Turbo T2 contributes to a more severe ejection port signature, increasing the overall severity of the signature on the standard MK18 weapon system. This phenomenon also occurs with the SilencerCo Saker and the full-size Polonium on the MK18, albeit more severely. Despite the less severe ejection port signature, caution should be exercised by the weapon operator. The signatures measured at the shooter’s ear are presented below.
6.98.1.2 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 significant rarefaction for Shots 1 through 5. The real sound impulse (momentum transfer potential) histories at the ear from the same 6-shot test are shown in Figure 4. Again, full and short timescales are shown.
Figure 3a. YHM Turbo T2 5.56x45mm NATO MK18 Automatic Rifle Ear Sound Pressure Signature
Figure 3b. YHM Turbo T2 5.56x45mm NATO MK18 Automatic Rifle Ear Sound Pressure Signature, Short Time Window
Figure 4a. YHM Turbo T2 5.56x45mm NATO MK18 Automatic Rifle Ear Sound Impulse Signature
Figure 4b. YHM Turbo T2 5.56x45mm NATO MK18 Automatic Rifle Ear Sound Impulse Signature Peaks
There are significant events shown in the above figures, and two primary conclusions should be noted by the reader:
The FRP, to the shooter, is not severe with the YHM Turbo T2 on this weapon system. Therefore, the weapon operator will not be subjected to greater hearing damage risk during the first shot, when compared to subsequent shots, on this weapon system. This analysis is consistent with that previously presented at the muzzle (for bystanders) with this silencer on this weapon system.
The back pressure generation (flow restriction) from the Turbo T2 is significant. Note the significant late-time rarefaction in the pressure waveforms measured near the shooter’s head in Figure 3b. This late time rarefaction occurs after significant positive phase pressure originating from the ejection port of the weapon. The significant positive phase pressure results in excessive impulse accumulation (Figure 4). Extremely similar phenomena is also noted in testing of both the Otter Creek Labs Polonium (Review 6.75) and the SilencerCo Saker 556 (Review 6.53).
PEW Science Research Note 4: Like in the measurements at the muzzle, the Turbo T2 exhibits increased signature severity as the shot string continues, to the shooter. This increase in signature severity may be a result of the Turbo T2’s design possessing a large ratio of expansion volume to baffle surface area, particularly early in the stack. More research is needed.
Holistic suppression performance comparisons on the MK18 weapon system are examined in the section below.
6.98.2 Suppression Rating Comparison (5.56x45mm from the MK18)
Figure 5 presents a comparison of the PEW Science Suppression Rating of the YHM Turbo T2 with the included Phantom Q.D. muzzle brake mount 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 5. Suppression Rating Comparisons of the YHM Turbo T2 and other silencers, Using PEW-SOFT 5.56x45mm Supersonic Test Data and PEW Science Analysis
From the above data, it can be concluded that the YHM Turbo T2 has higher sound signature suppression performance to bystanders than many of the other silencers shown, but is unable to match the suppression performance to bystanders of the Otter Creek Labs Polonium (Review 6.75), Polonium-K (Review 6.95), Surefire SOCOM556-RC2 (Review 6.52), and SilencerCo Saker 556 (Review 6.53). Nonetheless, it does outperform some other dedicated-bore 5.56x45mm silencers in bystander suppression, like the KAC QDSS-NT4 (Review 6.78), KGM R556 (Review 6.60), and all of the rifle silencers from HUXWRX / OSS on the standard MK18 host weapon, to date.
PEW Science Research Note 4: The YHM Turbo T2 is unable to suppress signature as well to bystanders as the SOCOM556-RC2, even by possessing more flow restriction. This inefficiency is similar to that possessed by the SilencerCo Saker 556, though the Turbo T2 does exhibit less flow restriction than the Saker.
Interestingly, the Turbo T2 subjects the shooter to almost the same hearing damage risk potential on the MK18 as the Dead Air Sandman-S (Review 6.92) and the Surefire SOCOM762-RC2 (Review 6.73); two silencers with similar performance on the MK18 weapon system due to their significant over-bore. Those two silencers are louder to the shooter due to their loud muzzle signature; the YHM Turbo T2 is just as damaging to the shooter’s ears due to its significant flow restriction and resulting ejection port wave coalescence. This represents a typical case of differing performance balance on the platform. It should be noted that such performance differential is not always present, and depends on individual silencer designs.
It is important to note that the signature to which the shooter’s ear is subjected is a function of both ejection port and muzzle signature. When the silencer’s endcap is in closer proximity to the shooter, the severity is increased. The coalescing of the ejection port overpressure with the primary muzzle blast exacerbates the severity of the signature at the shooter’s head position. It is not ejection port signature, alone, that dictates the signature measured at the shooter’s head position.
Bystanders may perceive the YHM Turbo T2 to be quieter than many silencers shown in Figure 5 when fired on the MK18 host weapon. Personnel firing the weapon may experience hearing damage risk on par with that from using the Dead Air Sandman-S, Surefire SOCOM762-RC2, or Q Trash Panda. Note that late-time gas blow back, a symptom often presenting with silencers exhibiting high back pressure, may be more severe with the Turbo T2 than with those aforementioned silencers, despite their signatures generating similar inner ear damage risk to the weapon system operator.
6.98.3 Review Summary: YHM Turbo T2 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 YHM Turbo T2 mounted with the muzzle brake mount achieved a composite Suppression Rating™ of 29.8 in PEW Science testing. As with all weapon systems, the user is encouraged to examine both muzzle and ear Suppression Ratings.
PEW Science Subjective Opinion:
The YHM Turbo T2 is a somewhat compact 5.56mm machine gun rated rifle silencer that possesses competitive sound signature suppression performance with many silencers on the market, while possessing higher back pressure compared to some designs. The silencer is capable of using mounts from other manufactures, which may enhance utility to some users. Without a mount, the Turbo T2 weighs only 10.4 ounces and is 5.5 inches long.
The YHM Turbo T2 is an updated version of the legacy YHM Turbo silencer that includes “universal” rear mount adaptability, as well as enhanced flash hiding features on its distal orifice. The Turbo T2 possesses three primary baffles and a fourth perforated Inconel steel blast baffle. The perforated blast baffle provides additional expansion volume for 5.56x45mm jetting in early time, while also shielding the primary baffles in the stack from direct blast jet impingement.
The sound signature suppression performance of the YHM Turbo T2 on the MK18 weapon system is competitive; the suppression performance to bystanders (muzzle Suppression Rating) is higher than many silencers on the market. It should also be noted that the back pressure (flow restriction) of the Turbo T2 is significant. Users fielding such silencers on the AR15 weapon system may be advised to take flow restriction into consideration. Methods by which users may mitigate some of the adverse effects of high silencer flow restriction on the MK18 include increased buffer mass, spring force, and/or adjustable gas port orifice size. So-called “tuning” of the AR15 weapon system, for both suppressed function and optimized signature, is outside the scope of this article.
The rear of the Turbo T2 is threaded for universal mount adaptation. The user may choose to install third-party adapters compatible with the 1.375”-24tpi system. This feature allows for significant adaptability of the silencer, should the included Phantom Q.D. adapter not be used.
Due to the construction of the YHM Turbo T2, PEW Science postulates that it can withstand relatively severe firing schedules. However, PEW Science has not subjected the Turbo T2 to severe automatic firing schedules and encourages the user to contact the manufacturer for guidance prior to use in such applications.
In this review, the Turbo T2 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.
