SSS.6.117 - Abel Company Theorem-L and the Savage Model 10 PC .308

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Abel Company Theorem-L on a Savage Model 10 .308 with 20-in Barrel

The Theorem-L is manufactured by Abel Company. It is a 30 caliber centerfire rifle silencer, intended to suppress many cartridges with projectiles appropriately sized to travel through the bore, up to and including 300 PRC. It has a 1.75-inch diameter and is 8.625 inches in length. The rear of the silencer is threaded with the so-called HUB universal diameter and pitch, allowing the use of a variety of mounting solutions. With the included direct thread mount, the silencer’s length increases to 8.8 inches. The silencer is tubeless; the entirety of the silencer is constructed of 6AL4V (Grade 5) Titanium. The end cap is removable. As tested, the silencer weighs 13.9 ounces and the direct thread mount weighs 2.0 ounces, for a total system weight of 15.9 ounces. The Theorem-L can be obtained from Abel Company.

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-Abel-056-001-23. Therefore, data pertaining to the Theorem-L in this Sound Signature Review is published with the express written permission of Abel Suppressor Co., LLC.

This review contains single-test results using the Theorem-L with the direct thread mount on the Savage Model 10 Precision Carbine rifle, chambered in .308WIN with a 20-inch barrel. Federal XM80 149gr ammunition was used in the tests.

  • Section 6.117.1 contains the Theorem-L test results and analysis.
  • Section 6.117.2 contains back pressure and Suppression Rating comparisons with selected .30 rifle silencers possessing a PEW Science Back Pressure Metric, Ω [Pa-1] in Omega Zone 6 and above. An updated Ω metric chart for the full suite of publicly evaluated .30 rifle silencers is also provided in this section. Further information about the Ω metric and Omega Zones can be obtained in PEW Science Research Supplement 6.40 (Public Article).
  • Section 6.117.3 contains the review summary and PEW Science opinions.

Summary: When paired with the Savage M10 20” .308 and fired with Federal XM80, the Abel Company Theorem-L, mounted with the direct thread mount, achieved a Suppression Rating™ of 47.2 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

6.117.1 Abel Company Theorem-L Sound Signature Test Results

A summary of the principal Silencer Sound Standard performance metrics of the Theorem-L 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. Abel Company Theorem-L Sound Metric Summary

 

6.117.1.1 SOUND SIGNATURES AT THE MUZZLE

Real sound pressure histories acquired with PEW-SOFT™ are shown below. 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 5 shots with the Theorem-L 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 5-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. Abel Company Theorem-L Bolt Action Rifle Muzzle Sound Pressure Signature

Fig 1b. Abel Company Theorem-L Bolt Action Rifle Muzzle Sound Pressure Signature, Short Time Window

Figure 2a. Abel Company Theorem-L Bolt Action Rifle Muzzle Sound Impulse Signature

Figure 2b. Abel Company Theorem-L Bolt Action Rifle Muzzle Sound Impulse Signature, Short Time Window

Figure 1b shows a 2.1 millisecond long portion of the first round sound pressure signature of the Abel Company Theorem-L as measured 1.0 m left of the muzzle. There are several significant waveform features labeled:

  1. Internal combustion within the silencer reaches a peak of 125.4 dB.

  2. The end cap exit event, consisting of bullet shock and the initial jet, results in a peak overpressure magnitude of 141.3 dB.

  3. There is relatively early FRP divergence; primary FRP jetting reaches a peak magnitude of 147.0 dB.

This is a somewhat typical sequence observed when firing supersonic .308WIN ammunition from a bolt-action rifle with an attached silencer that exhibits relatively high flow restriction (back pressure). Internal silencer design can significantly influence the measured timing and pressure amplitudes. Preliminary back pressure comparisons are shown in Section 6.117.3 of this review, with the PEW Science Back Pressure Metric, Ω [Pa-1]. Note that weapon system influence is a function of both Ω and early-time wave propagation factors which may be measured inside the system, in close proximity to the muzzle orifice. These factors include the so-called PEW Science Alpha parameter; a subject of future research. For example, the Theorem-L possesses a ported blast baffle, and when used with the included direct-thread mount, early time gas dynamics and their influence on weapon function may differ from some silencers present in Omega Zone 7.

The Abel Company Theorem-L presents relatively typical suppression performance in this combustion regime, for a modern 30 caliber rifle silencer of its size. The Theorem-L is approximately 8.8 inches long with its tested direct thread mount. The suppression performance of the Theorem-L on this platform, holistically, is best compared with the Aero Precision Lahar-30L (6.112), Thunder Beast ULTRA 9 (6.24) and the Otter Creek Labs PR30L (6.48). Both the ULTRA 9 and PR30L are similar in length to the Theorem-L, with the Lahar-30L being shorter, at 7.6 inches long.

PEW Science Research Note 1: As stated above, the performance of the Abel Company Theorem-L, for its size, is typical. It is intended to be a precision rifle silencer, and it possesses certain features to assist with achieving consistent gas dynamics, including a symmetrical blast baffle and strict concentricity measurements during the manufacturing process. The silencer is also designed to somewhat relieve early time pressure stagnation; it possesses significant porting in the blast baffle. The combination of these features may result in requisite performance improvements; however, PEW Science has not evaluated the precision of this silencer, nor its influence on semiautomatic weapon operation. It should be noted that the baffle notches in the stack are staggered in groups.

PEW Science Research Note 2: With regard to gas dynamics consistency, general impulse accumulation consistency is noted in the measured data (Figure 2a). However, it should be noted that slightly abnormal early-time impulse accumulation is measured beginning in Shot 4 of the 5-shot string (30.8 ms, Fig 2b). The accumulation is also measured in Shot 5, albeit at a reduced amplitude. Due to the relative consistency of the remainder of the combustion histories, PEW Science postulates that abnormal accumulation in the noted time regimes, in later shots, may be due to a higher temperature gradient reducing efficiency through a high-flow region of the stack facilitated by porting. It is possible that this combustion propagation anomaly may only present upon continued firing schedule. It is notable, because the severity of Shot 4 and Shot 5, to bystanders, are postulated to be higher than the rest of the shot string, in accordance with PEW Science inner ear modeling. The first-round-pop (FRP) of the Theorem-L, to bystanders, is noticeable, and more severe than subsequent shots. In this test, the combustion anomalies in Shot 4 resulted in FRP-like inner ear damage risk potential, to bystanders.

Consistent with these measured pressure and impulse waveform features, the computed PEW Science Omega Metric is relatively high, placing the silencer in Omega Zone 7. Relative Suppression Rating and flow restriction (back pressure) data is presented in Section 6.117.2 of this review.

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 has made a concerted effort to characterize the FRP phenomenon with true physiological human inner-ear response analyses. Additional PEW Science Member Research Supplements containing this information are released periodically.

6.117.1.2 SOUND SIGNATURES AT SHOOTER’S EAR

Real sound pressure histories from the same 5-shot test of the Theorem-L suppressor 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 5 shots are shown in Figure 3. The primary sound signature history is shown on the left. A zoomed-in timescale is displayed on the right, in the region of peak sound pressure for Shot 1, Shot 2, and Shot 4. 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. Abel Company Theorem-L Bolt Action Rifle Ear Sound Pressure Signature

Figure 3b. Abel Company Theorem-L Bolt Action Rifle Ear Sound Pressure Signature, Short Time Window

Figure 4a. Abel Company Theorem-L Bolt Action Rifle Ear Sound Impulse Signature

Figure 4b. Abel Company Theorem-L Bolt Action Rifle Ear Sound Impulse Signature, Short Time Window

The combustion anomaly measured during Shot 4 at the muzzle is mirrored at the shooter’s ear. Note that the pressure divergence during Shot 4 at approximately 31.5 ms (Fig. 3b) is also expressed in impulse space in Figure 4b. This muzzle-driven behavior (occurring after internal weapon system combustion and propagating rearward toward the shooter) did not adversely influence inner ear damage risk to the shooter during this test. This is important to note, because the combustion anomaly may be due to prolonged strings of fire; shooter risk not being influenced by this potential phenomenon is due to wave decay and sound field shape on this host weapon barrel length. Whether or not the anomaly also presents with other cartridges or barrel lengths is currently unknown. PEW Science postulates impact to the shooter to be minimal.

PEW Science Research Note 3: The Theorem-L does not produce as significant increased hearing damage risk potential to the shooter during FRP as it does to bystanders, on the tested weapon system. The FRP to the shooter is less severe. And, as stated above, the late-shot combustion anomalies are inconsequential to shooter inner ear damage risk.

PEW Science Research Note 4: The similarities of the Theorem-L signature to that of the Aero Precision Lahar-30L are significant. This is notable due to the size difference of the two silencers. The similarities in signatures occur in both the muzzle and ear measurements. The silencers use baffles of different shape, quantity, orientation, spacing, and size. The comparison of the two silencers illustrates the efficiency of different rifle silencer designs with regard to pure suppression performance, due to the tested platform being a bolt-action rifle.

As typical, the overall sound signature measured at the shooter’s ear possesses significantly less amplitude in both the pressure and impulse regimes than the signature measured at the muzzle (refer to Table 1). Furthermore, the application of both pressure and impulse at the shooter’s ear is delayed when compared to the pressure and impulse at the weapon muzzle. The combination of varying amplitude and rise time to peak amplitude influences the response of the human ear.

It is extremely important to note that muzzle signature influences the signature to the weapon operator. This is a test on a bolt-action rifle. Similar jetting phenomenon measured at the muzzle propagates toward the shooter. The standoff of the endcap to the shooter, as well as angle of incidence of the pressure (blast) waves, result in exponential decay of hearing damage risk when compared to personnel adjacent to the muzzle.

6.117.2 Relative Suppression Rating and Back Pressure Comparisons (.30 Rifle Silencers)

The Abel Company Theorem-L suppressor is intended to offer significant sound signature suppression that is consistent, while offering somewhat lower back pressure than similarly sized designs. PEW Science has developed an empirical relation to quantify the back pressure (flow restriction) of silencers. Figure 5 and Figure 6 show supersonic suppression and back pressure comparisons between selected 7.62mm (30 caliber) rifle silencers shown in public PEW Science Sound Signature Reviews, as of the date of this review publication. The results shown in Figure 5 and Figure 6 are calculated from real test data acquired with PEW-SOFT. Please note the following:

  1. The PEW Science Back Pressure Metric, Ω [Pa-1], may be generated for any silencer and suppressed weapon system using any suitable raw external overpressure signature data acquired 1.0 m left of the silencer end cap. PEW Science highly recommends data acquisition in accordance with The Silencer Sound Standard.
  1. Omega Zones are presented in Table 3, below, which are intended to provide guidance to weapons developers, silencer designers, and end-users, with regard to flow restriction characteristics of different silencer designs. It is very important to note that silencers possessing a relatively high Ω can still provide functional use on weapon systems. Some weapon systems are more sensitive to Ω than others.
  1. It is important to note that a silencer’s Omega Zone can shift when using a mounting scheme that differs from that used in the testing referenced in the published PEW Science Sound Signature Reviews. This phenomenon occurs due to some silencer mounting schemes significantly influencing flow restriction with some silencer designs.
  1. The theoretical lower limit of flow restriction, or so-called "zero back pressure" would be represented by the unsupressed state, Ω = 0 [Pa-1].
  1. PEW Science acknowledges that other dynamic events occur within a suppressed weapon system that can also influence weapon function. Therefore, PEW Science acknowledges that Ω is not the sole parameter one must consider for total supppressed weapon system operation. However, PEW Science postulates that the Ω metric influence can be significant. Note that weapon system influence is also a function of early-time wave propagation factors which may be measured inside the system, in close proximity to the muzzle orifice. These factors include the so-called PEW Science Alpha parameter; a subject of future research.
  1. The Back Pressure Metric relations are most easily viewed on a logarithmic scale (See Figure 6).

Figure 5. Omega Back Pressure Metric And Suppression Rating Comparisons Of .308 Rifle Silencers Using PEW-SOFT Data and Analysis

As stated above, the PEW Science Back Pressure Metric is most easily viewed on a logarithmic scale. The metric is nonlinear; the shape of the trend in the data presented in Figure 6, below, illustrates the potential thresholds of extreme flow rate (approaching the unsuppressed state) and extreme flow restriction (approaching the trapping of the maximum amount of combustion byproducts in a system).

Figure 6. Omega Back Pressure Metric Comparisons Of .308 Rifle Silencers Using PEW-SOFT Data and Analysis

Omega characterizes silencer back pressure. It is important to note that back pressure is not blow back. The back pressure of a silencer is the flow restriction it introduces in a suppressed weapon system. The blow back phenomenon that can occur during the use of a suppressed weapon system is caused by the reciprocating system actuating too early relative to overpressure decay within the weapon system, resulting in exposure of excessive internal system overpressure to atmosphere. Some weapons may be tuned to function well with silencers in a high Omega Zone. Some weapons may require low-Omega silencers due to constraints in their operating system(s). Omega metric technical details can be found in PEW Science Public Research Supplement 6.40.

Table 2. PEW Science Back Pressure Metric Omega Zones And Suppressed Weapon System Functional Descriptions

As stated above, weapon system influence is a function of both Ω and early-time wave propagation factors which may be measured inside the system, in close proximity to the muzzle orifice. These factors include the so-called PEW Science Alpha parameter; a subject of future research. For example, the Abel Company Theorem-L possesses a ported blast baffle, and when used with the included direct-thread mount, early time gas dynamics and their influence on weapon function may differ from some silencers present in Omega Zone 7.

The suppression performance of the Theorem-L on this platform, holistically, is best compared with the Aero Precision Lahar-30L (6.112), Thunder Beast ULTRA 9 (6.24) and the Otter Creek Labs PR30L (6.48). Both the ULTRA 9 and PR30L are similar in length to the Theorem-L, with the Lahar-30L being shorter, at 7.6 inches long. Silencers that approach (but do not achieve) the supersonic 7.62x51mm suppression performance of the Theorem-L include the Liberty Precision Machine Anthem-S (6.79), CGS Helios QD (6.13), and the Silencer Central Banish 30 Gold (6.69). Note that although the Banish 30 Gold is only slightly shorter than the Theorem-L, the Anthem-S and Helios QD are significantly shorter.

PEW Science Research Note 5: As previously noted, both the Anthem-S and Helios QD are slightly shorter than the Lahar-30L. The Banish 30 Gold, ULTRA 9, and PR30L are all longer. The Aero Precision Lahar-30L demonstrates one of the most significant examples of performance-based design optimization in the Silencer Sound Standard research pedigree, to date. Not only does it match the performance of longer silencers, but it also eclipses the performance of some of them. For example, the Lahar-30L is quieter to both the shooter, and to bystanders, than the Rugged Surge (6.22); a silencer that is 9 inches long. The Lahar-30L significantly outperforms the Dead Air Sandman-L (6.23), which is another 9 inch long silencer. The Lahar-30L also outperforms some silencers that are larger in diameter and length in this combustion regime, such as the Q Thunder Chicken (6.20). These comparisons are notable.

PEW Science Research Note 6: The Abel Company Theorem-L is in Omega Zone 7 (Figure 6), which indicates that it exhibits relatively high flow restriction. Interior expansion volume, coupled with the quantity and number of baffles, contribute to this lower flow rate.

PEW Science urges the reader not to misconstrue a low Omega metric with the mirroring of unsuppressed weapon function, nor a high Omega Metric with absolute use prohibition on semi-automatic systems. Each weapon system may experience varying sensitivity to different Omega Zones and users may exhibit varying preference for weapon system function and operability. The Zones are provided by PEW Science to assist the reader with determination of postulated applicability of silencer types, as some users may only have experience with certain silencers. The Omega Metric is one performance indicator; it allows overall flow rate phenomena to be categorized independently from sound signature suppression performance. Note that weapon system influence is also a function of early-time wave propagation factors which may be measured inside the system, in close proximity to the muzzle orifice.

It is extremely important to note that peak sound pressure [dB], peak sound impulse [dB-ms], and Omega (Ω) [Pa-1], alone, do not determine the sound supression performance of a silencer. It is the combination of these and other waveform parameters that form the total sound signature and the influence on human inner ear response. The PEW Science Suppression Rating computation considers all of these factors.

6.117.3 Review Summary: Abel Company Theorem-L on a Savage Model 10 .308 with 20-in Barrel

When paired with the Savage M10 20” .308 and fired with Federal XM80, the Abel Company Theorem-L, mounted with the direct thread mount, achieved a Suppression Rating™ of 47.2 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 Abel Company Theorem-L is a full-size 30 caliber precision rifle silencer that possesses significant sound signature suppression performance in this combustion regime. The silencer is relatively lightweight for its size. The Theorem-L possesses a modular rear mounting interface that may be used with a variety of mounting solutions and muzzle devices. The end cap of the silencer is also removable.

The Abel Company Theorem-L presents relatively typical suppression performance in this combustion regime, for a modern 30 caliber rifle silencer of its size. The Theorem-L is approximately 8.8 inches long with its tested direct thread mount. The performance of the Theorem-L on this platform, holistically, is best compared with the Aero Precision Lahar-30L, Thunder Beast ULTRA 9, and the Otter Creek Labs PR30L. Both the ULTRA 9 and PR30L are similar in length to the Theorem-L, with the Lahar-30L being shorter, at 7.6 inches long.

The Theorem-L is intended to be a precision rifle silencer, and it possesses certain features to assist with achieving consistent gas dynamics, including a symmetrical blast baffle and strict concentricity measurements during the manufacturing process. Manufacturer reports indicate low impact to firearm precision with the use of the Theorem-L. The silencer’s blast baffle is also ported; when used with the included direct-thread mount, early time gas dynamics and their influence on weapon function may differ from some of the aforementioned silencers that exhibit similar external gas dynamics. It should be noted that PEW Science has not evaluated this silencer’s influence weapon precision, nor its influence on semiautomatic weapon operation.

The rear mount threading of the Abel Company Theorem-L is 1.375”-24tpi; relatively common in many modern rifle silencers. As a result of this common modular interface, a plethora of mounting systems may be used. The performance of the Theorem-L may be influenced by mounting system choice. The user’s choice of mount may balance system weight, length, durability, utility, and even back pressure of the silencer. The data presented by PEW Science in this Sound Signature Review was measured with the direct thread mount.

In this review, the Theorem-L performance metrics depend upon suppressing a supersonic centerfire rifle cartridge; no easy 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 .308WIN cartridge are significant; the measured pressure and impulse magnitudes, and their durations, illustrate this fact.

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.