White Sound Defense Muzzle Device
FOSSA-556 Review

April 24, 2013

White Sound Defense Muzzle Device Review

The increased popularity and potential ban of the AR style rifle has consumed the market and made it hard to find an AR at a reasonable price.  This sudden surge in demand has also driven an increased need in parts for everyone wanting to build their own rifle or those wanting to upgrade a bare bones (entry level) rifle that they just purchased.  When I think of the key features that stand out on an AR style rifle, the muzzle device is clearly on the list and often not given enough consideration.  I know I'm guilty of spending too much time looking at sights, rails, rail mounted accessories, optics and buttstocks than I should, and not focusing enough time on muzzle devices which perform critical roles in the performance of a rifle such as reducing felt recoil, muzzle rise and flash signature.


In this review I wanted to take a close look at a new muzzle device on the market made by White Sound Defense.  White Sound Defense is relatively new to the market and at the moment they focus on Glock parts, lubricants/conditioners and a single muzzle device.   The White Sound Defense Muzzle Device is called the FOSSA-556™ and is designed for .223 / 5.56 barrels with a 0.5" x 28 tpi thread.  It is machined from a solid piece of 17-4PH stainless steel and comes with a titanium aluminum nitride coating.  The  FOSSA-556 can be found online at this link for $109 plus S&H.

During my reviews I like to compare my results to the manufacturer's claims where possible so the following text in colored italics was taken directly from the White Sound Defense website on 2/15/13 and gives a Description, Features, and Specifications for the FOSSA-556 Muzzle Device.  The , and are my way to show agreement and keep up with details that I have covered in this review with either photos, commentary or both.


  • The FOSSA-556™ is a high performance multifunction muzzle device optimized for the fighting rifle. It suppresses muzzle flash and vents gasses away from the ground to limit dust disturbance. It also eliminates muzzle rise and reduces recoil getting the shooter back on target faster, all without increasing concussion or noise.
  • Generally, the first priority of an operator is to avoid being taken out of the fight. As such, the ability of this device to reduce muzzle flash and dust signature has been maximized. This multifunction device is unique in that it matches or exceeds the flash suppression effectiveness of the best single function flash suppressors.
  • The second priority is to improve the effectiveness of fire. Muzzle climb is countered by redirecting propellant gasses with an upward bias. Recoil is reduced by the exclusive tapered vents that force a large percentage of propellant gas to the sides much like a traditional recoil compensator. However, unlike traditional recoil compensators there is no additional concussion or volume.
  • The FOSSA-556™ has been designed with great care regarding accuracy. It has been engineered and tested to ensure the highest level of performance.
  • Additionally, this device has been tuned to avoid the annoying ringing sound common with other flash suppressors.
  • This version of the FOSSA-556™ is made from 17-4PH stainless steel with a titanium aluminum nitride surface coating. While this might be over-kill for some applications, this finish is extremely durable and provides a low friction surface to minimize adhesion of carbon and copper.
  • All muzzle devices represent design compromises. The best design for a competition rifle is not the best design for a fighting rifle. This design is optimized for a fighting rifle. There is no other device that does so much so well.


  • Nominal Flash Signature
  • Mitigated Dust Signature
  • Fully Compensated Muzzle Rise
  • Reduced Rearward Recoil
  • No Increase in Concussion or Noise
  • No Annoying Ringing Sound

Specifications (the specifications were not listed in this format, but I like to look at them this way)

  • Model: FOSSA-556™
  • SKU: FCX-FHB-556528-001
  • Caliber: .223 / 5.56 barrels
  • Thread Size: 0.5" x 28 tpi measured 0.70" deep
  • Material: 17-4PH Stainless Steel
  • Surface Coating: Titanium Aluminum Nitride
  • Length: 2.18"
  • Diameter: 0.86"
  • Weight: 3.1 ounces
  • Retail Price: $109

When you purchase a White Sound Defense FOSSA-556 Muzzle Device, it comes packaged as shown below which is simple and cost effective.  Inside the package is a single part, the muzzle device.  Since I would consider this to be a premium level muzzle device based on price, it would have been nice for White Sound Defense to include a new crush washer for installation.  It is critical to clock the muzzle device on your barrel and a crush washer is a simple and easy way to accomplish this.  The label on the package gives the critical information such as model number (FOSSA-556™), SKU number (FCX-FHB-556528-001), caliber (.223 / 5.56) and internal threads (0.5" x 28 tpi).

Figure 1
White Sound Defense Muzzle Device Review

These next three photos give you a good look at the ends and top of the FOSSA-556™ Muzzle Device. The device measures 2.18" in length and 0.86" in diameter.  It comes with 3/4" wrench flats at the base for installation.

Figure 2                                               Figure 3                                              Figure 4
White Sound Defense Muzzle Device Review   White Sound Defense Muzzle Device Review   White Sound Defense Muzzle Device Review

The FOSSA-556™ Muzzle Device is made from 17-4PH stainless steel and weighed in at 3.1 ounces.  This was slightly heavier than a couple I had on hand such as the standard A2 at 2.1 ounces, YHM Phantom 5C2 at 2.1 ounces and a Ruger Birdcage at 2.54 ounces.  I checked the weight against the Smith Vortex at 2.9 ounces, so the FOSSA-556 is on the high end range of muzzle device weights, but in reality we are only talking about an extra ounce compared to the lightest ones.

Figure 5
White Sound Defense Muzzle Device Review

If you take a close look at the muzzle device you will see it is nicely machine and titanium aluminum nitride coated to a dark gray appearance.  This coating is a hard durable coating that should hold up to the temperatures you would get at the muzzle of your rifle.  The internal thread is the standard 1/2" x 28 threads per inch (tpi) and measured 0.70" deep.

Figure 6                                                             Figure 7      
White Sound Defense Muzzle Device Review   White Sound Defense Muzzle Device Review

The photo below shows the end of the FOSSA-556™ Muzzle Device and you can see several of the critical features in this view.

  • Mitigate Dust Signature/Disturbance - Notice that when the device is installed (the direction up in the photo below should be up on your barrel), there is no direct path of gas towards the ground.  The bottom prong is cut to a ~125 degree wedge so that as pressure is released out of the barrel, the paths of least resistance are laterally and up.

  • Fully Compensated Muzzle Rise - Since the pressure has no resistance due to the upper vented area, the gas pressure can push on the lower prong to help reduce muzzle rise.

  • No Annoying Ringing Sound - Notice that there are holes drilled in each prong and one hole looks deeper than the rest.  After contacting White Sound Defense, they explained that the deeper hole helps to change the resonate frequency which in turn helps to reduce the ringing sounds you get from some muzzle devices.

Figure 8

The photo below shows the top of the White Sound Muzzle Device and can be used to point out a couple more features.

  • Reduced Rearward Recoil - The gap between the prongs is larger at the rear than the front.  White Sound Defense states that the tapper on these vents loses about 25% of the width as it reaches the end.  You can see there is a slight taper on the prongs which gives a small amount of breaking surface for the gas pressure to act on.  Based on the geometry of the device, I can see there would be a reduced rearward recoil, but it would be relatively small compared to others designed specifically for recoil reduction.

  • No Increase in Concussion or Noise - Increased in concussion or noise is typically due to sound waves bounding off surfaces back to the shooter.  Since the taper on the prongs is very small, there are no surfaces that would come close to bouncing back the sound waves.

Figure 9

Range Tests

For range testing, I took a look at several different barrel lengths.  Throughout my range testing, I used WPA (Wolf Performance Ammunition) 55 gr FMJ ammunition.  I first tried to compare the White Sound Defense FOSSA-556 Muzzle Device against the A2 flash hider on my Colt Sporter II rifle with a 20" barrel.  The photos below show the FOSSA-556 installed on this rifle.  White Sound Defense advertises this muzzle device as being optimized specifically for a "fighting rifle".  Although I wouldn't consider my Sporter II a "fighting rifle", I still wanted to check it out with this barrel length.  I found there to be very little difference between the A2 and the FOSSA-556 with regard to muzzle rise and felt recoil.  Since this rifle has a 20" barrel, I didn't expect to see any significant difference due to the added barrel weight.  Also, I was not able to detect any significant difference in muzzle flash during my night range test.

Figure 10
White Sound Defense Muzzle Device Review

Figure 11
White Sound Defense Muzzle Device Review

Next I installed the FOSSA-556 muzzle device on a 16" barrel and performed several tests to compare the difference between having this device and not having it installed on the barrel.  Since I didn't have any instruments to determine true forces associated with muzzle breaking and muzzle rise compensating, I had to judge the differences by shooting the rifle myself, so I placed the quad rail very lightly in my open hand and held the grip very light.  While holding the rifle this way and with it not against my shoulder, I fired several rounds.  I had a couple of other shooters (engineers who were very critical) watch the recoil of the rifle and we were all able to come to a common conclusion that the FOSSA-556 does help to compensate against muzzle rise and reduce recoil by a slight amount.  As a test, I then rotated the FOSSA-556 so the top of the device pointed down (opposite of how it is supposed to be installed) and it seemed to increase the muzzle rise which was good indication of it's effectiveness.

Figure 12
White Sound Defense Muzzle Device Review

Figure 13
White Sound Defense Muzzle Device Review

I repeated the same test above with the FOSSA-556 installed on my SBR with an 11.5" barrel and as the rifles got shorter and lighter, I feel the muzzle rise compensating effect was more apparent.  Since the type of comparison I was doing is not an exact science, I didn't try to make a comparison against an A2 flash suppressor.

Figure 14
White Sound Defense Muzzle Device Review

To evaluate how well the FOSSA-556 works to suppress the muzzle flash, I took some video using two barrel lengths (16" and 11.5") and compared it against "no" device and an A2 flash suppressor.  This next photo shows the flash from a 16" barrel with no muzzle device.

Figure 15 - 16" Barrel with No Muzzle Device
White Sound Defense Muzzle Device Review

The A2 Flash Suppressor did a good job with this barrel length, but there was still some apparent flash at the muzzle.

Figure 16 - 16" Barrel with A2 Flash Suppressor
White Sound Defense Muzzle Device Review

The White Sound Defense FOSSA-556 Muzzle Device made the flash nearly non detectable.  In each of these comparisons, I shot 5 times for each configuration and in the photos I show the largest looking flash signature out of the five shots.

Figure 17 - 16" Barrel with White Sound Defense FOSSA-556 Muzzle Device
White Sound Defense Muzzle Device Review

This next photo shows the flash for a Short Barrel Rifle (SBR) with an 11.5" barrel and no muzzle device.  You can see that you don't get a full powder burn while the bullet is in the barrel.  The flash signature was actually very impressive.  After seeing this flash signature for a 11.5" barrel, I was curious to see how well the two muzzle devices would tame this flash.

Figure 18 - 11.5" Barrel with No Muzzle Device
White Sound Defense Muzzle Device Review

Overall I was impressed with the A2, but I did get one shot out of five that produced the clearly larger flash signature below.

Figure 19 - 11.5" Barrel with A2 Flash Suppressor
White Sound Defense Muzzle Device Review

The FOSSA-556 produced what I believe were overall reduced flash signatures than the A2.  Honestly, I was amazed at how well White Sound device was able to reduce the fire ball into a burst of sparks.  Keep in mind you are looking at the largest signature of the five shots recorded.  The sparks you are seeing are what is referred to as 'primary' light emission and comes from hot carbon and incompletely burned powder which is why it looks like little comets or sparks.  Unfortunately, they can't be extinguished by a muzzle device.

Figure 20 - 11.5" Barrel with White Sound Defense FOSSA-556 Muzzle Device
White Sound Defense Muzzle Device Review

It is hard to appreciate the flash reduction of the FOSSA-556 just by looking at the photos above, so I included this next video to show all the shots fired with the 16" and 11.5" barrel lengths during this night time range test and you can form your own opinion on the effectiveness.


Bottom Line:

The White Sound Defense FOSSA-556 Muzzle Device appears to be a quality product that has a design backed by engineering principles.  In my range tests, I believe the FOSSA-556 is effective in reducing muzzle rise, felt recoil and without a doubt muzzle flash.  These benefits are best seen on shorter barreled rifles which is why White Sound Defense clearly states it is "optimized for a fighting rifle".  I'm still amazed at how well this muzzle device was able to tame the fireball that comes out of the end of a short barrel rifle and this ability alone makes it a great muzzle device.  When you couple this ability with the other benefits of reduced recoil, reduced muzzle rise, minimal dust signature and other sound minimizing aspects, the White Sound Defense FOSSA-556 Muzzle Device is something you should consider putting on your fighting rifle.

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