Good afternoon everyone and welcome back to TFB’s Silencer Saturday brought to you by Yankee Hill Machine, manufacturers of the new YHM R45 Multi-Host Suppressor. Last weekend we started off with an introduction to the latest SureFire rifle suppressor, Today we compare the SureFire SOCOM556 RC3 to the venerable SureFire SOCOM556 RC2 on different barrel lengths of gas operated carbines. Is SureFire’s next generation suppressor quieter than the RC2? Does barrel length matter? I think we all know the answer to that… but let’s dig in anyway.

More SureFire @ TFB:

• SILENCER SATURDAY #307: The SureFire SOCOM RC3 Suppressor
• The New SOCOM RC3 – SureFire’s First Low Back Pressure Suppressor
• SILENCER SATURDAY #274: Short Silencer, Long Barrel? Surefire SOCOM556-MINI2

SILENCER SATURDAY #308: Barrel Lengths and the SureFire SOCOM556 RC3

As a brief recap, the SureFire SOCOM556 RC3 is a low back pressure designed suppressor that has the exact same specifications of the SureFire RC2 suppressor. Known for their durability, repeatability, and solid mounting system, the SureFire suppressors have seen extensive use by both the military and law enforcement agencies around the world. The move to incorporate low back pressure technology using direct metal laser sintering was derived from the need to make the addition of a suppressor to a rifle system a more neutral event. That is, traditionally designed suppressors can force more pressure into the action, effecting the cyclic rate and ejecting toxic gasses towards the shooter.

In Silencer Saturday #274 we discussed the SureFire Mini SOCOM556 suppressor and barrel length choices for shorter suppressors. It is important to remember the basics of ammunition and projectiles; the length of the barrel has a dramatic effect on the velocity of the round. The explosion, or deflagration of powder that causes the bullet to be forced down the barrel, starts inside the cartridge, but continues down the length of the barrel. Faster burning powders is shorter/quicker than longer burning gun powders. For maximum efficiency, the bullet should stay in the barrel for most, if not all, of the burning of the gun powder. Otherwise, unburned powder is wasted as flash, noise, and unused pressure either at the muzzle or inside a suppressor.

For suppressor use, lower muzzle pressures are better to protect the life of the suppressor; higher temperatures and pressures will erode metal faster. In addition, higher muzzle pressures contained by a suppressor can have negative effects on the weapon’s action and increase toxic gases around the shooter’s face.

In my opinion, the shortest useable barrel length for a 5.56x45mm AR-15 is 11.5 inches. The MK18 (10.3″) crew will be along shortly to argue their points, but besides suppressor performance and longevity, terminal ballistic performance, especially for small bullets, is very velocity dependent. To achieve the best results, there needs to be enough barrel runway to achieve sufficient velocity.

For today’s testing, the difference between an 11.5″ barrel and a 14.5″ barrel is about 2,000 PSI at the muzzle. This gap is significant enough for a suppression comparison between the RC2 and the RC3, especially because the new SureFire silencer is built specifically to handle back pressure, The goal of these tests is to give you a better idea of what to expect based on the barrel length of the host you plan on suppressing.

I did conduct one unofficial test, which I cannot recommend you try at home. Like we pointed out last week, the segments that run the circumference of the RC3 end cap are the vents where the pressure is released forward of the muzzle. I took a bit of lubricating grease and plugged the vents before taking a single shot. Afterwards, the vents were completely free of grease. So for anyone who is skeptical of the internal gas flow geometry, they do work as advertised.

A final note about today’s testing; the muzzle brake mounts I am using are not the optimal setup for maximum flash suppression. I alluded to proper muzzle device selection last week, and now that SureFire has published their official PSA, we can discuss it here.

It has come up recently that the RC3 may exhibit suboptimal flash performance with closed-tine muzzle devices. The RC3 was designed to operate optimally with SureFire SOCOM open-tine adapters (SF3P, FH556RC, WARCOMP-556-1/2-28), and delivers unmatched flash reduction in this configuration. Gas flow dynamics in low-back-pressure suppressors are extremely complex and sensitive to the slightest change. As a result, the RC3 may have increased muzzle flash with closed-tine adapters and muzzle brakes (SFCT-556-1/2-28, WARCOMP-556-CTN-1/2-28, SFMB).

As you can see above, if you are concerned about flash reduction, under night vision for example, select an open-tine flash hider to maximize the internal gas flow geometry. Personally I still suggest avoiding the Warcomp flash hiders as mounts since they lack the labyrinth seals found on the three-tine and four-tine flash hiders (links below). I have some flash hiders on the way to compare the sound suppression between brakes and flash hiders as well.

Let’s review the numbers.

Specifications – SureFire SOCOM556 RC3

• Model: Surefire SOCOM556-RC3
• Manufacturer’s Page: https://www.surefire.com/socom556-rc3/
• MSRP: $1799
• Materials: Inconnel
• Finish: Cerakote
• Diameter: 1.5 in (3.8 cm)
• Length: 6.3 in (16.0 cm)
• Length added to weapon*: 3.8 in (9.7 cm)
  • * Actual length may vary, depending on which SureFire adapter is used
• Weight: 17.0 oz (482 g)

Features:

• 60% less back pressure
• Virtually eliminates explosive flash
• ast-Attach® design allows fast, secure, easy attachment and removal without tools
• Backward compatible with SureFire SOCOM Fast-Attach muzzle devices
• Durable Inconel construction delivers long service life

Specifications – SureFire SOCOM RC2 (Previous Model Comparison)

• Model: SOCOM556-RC2
• Manufacturer’s Page: https://www.surefire.com/socom556-rc2/
• MSRP:  $1,199
• Materials:
• Finish: OLC and Cerakote
• Diameter: 1.5″
• Length: 6.4″
• Length added to weapon: 3.8″
  • * Actual length may vary, depending on which SureFire adapter is used
• Weight: 17.0 oz
• Sound Data @ the shooter’s ear (from SureFire)
• 10.3″ – 137.74
• 14.5″ – 136 .40

Muzzle Devices:

• SF3P-556 Flash Hider Suppressor Adapter – Three-prong flash hider – $169
• FH556RC Flash Hider Suppressor Adapter – Four-prong flash hider – $169

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The difference between the RC3 and the RC2 was most apparent on the 14.5″ hybrid-mid KAC gas system. Because of the longer barrel and gas system, the powder is burned more completely, leaving less pressure change inside the suppressor. Leaving my left earplug partially removed, the RC3 was just slightly louder than the RC2. And since the human ear can only detect a 2-3 dB difference, I’d estimate the RC3 is louder at the ear by about two decibels on this rifle.

However, both the RC3 and RC2 are what the industry would consider “hearing safe” – somewhere below 140 dB. As a reminder, supersonic centerfire rifle cartridges will always require hearing protection, even with a suppressor.

On the 11.5″ barrel with a carbine-length gas system, the RC3 and RC2 performed almost identically, suppressing somewhere around 140 dB (based on my ears alone), I swapped back and forth between the two of them and could not tell the difference.

For a short-barreled carbine, these 6.4″ suppressors performed very nicely, knocking the blast down to acceptable levels. If you were forced to shoot a few rounds with this setup outside, without hearing protection, you’d probably walk away without serious injury. But that is not recommended and would be reserved for an emergency situation.

As I have said many times in previous reviews, we don’t purchase supersonic rifle suppressors for their absolute quietness. We suppress these carbines to drop the sound to safer levels, mask the overall signature from the enemy (or neighbors), and to make an overall more pleasant shooting experience.

From my perspective, the RC3 makes the biggest difference on shorter barrels, where the pressure change in the suppressor is the greatest. on the 11.5″ here was a noticeable shift in the cartridge ejection pattern which usually indicates a change in bolt speed and the speed of the bolt unlocking. So while the sound suppression level between the RC3 and RC2 is nearly identical, adding the RC3 to an already over gassed carbine will not cause additional pressure to be introduced into the system. Any changes in barrel length, gas system length, ammunition, or buffer weight may have an effect on suppressor performance.

Thanks for reading. Be safe, have fun, and we’ll see you back here next weekend for another Silencer Saturday.

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