White Sound Defense Muzzle Device
FOSSA-762™ Review

April 12, 2015

Back in April 2013, I performed a review on White Sound Defense's first muzzle device called the FOSSA-556™ which was a 5.56mm / .223 caliber device.  That device was a combination flash suppressor, muzzle rise compensator and had some muzzle break ability.  In my tests I felt confident that the FOSSA-556™ was effective with flash suppression and muzzle rise compensating, and I was very impressed with its flash reducing capability.  Recently White Sound Defense released the big brother to their original muzzle device.  This new muzzle device is intended for the 7.62mm / .30 caliber  barrels and is called the FOSSA-762™.  The photo below gives you a good look at this new .30 caliber device compared to the .223 caliber device and clearly the .30 caliber device is a significantly larger piece of hardware.

Figure 1

The new FOSSA-762™ looks to be a scaled up version of the FOSSA-556™ in all aspects.  The reason for the difference in surface finishes is that the FOSSA-762™ has the black oxide coating while the FOSSA-556™ has the titanium aluminum nitride finish.

                                     Figure 2                                                            Figure 3
 

 

Just to be clear, the new White Sound Defense Muzzle Device is called the FOSSA-762™ and is designed for .308 / 7.62mm barrels with a 5/8" x 24 tpi thread.  The device is machined from a solid piece of 17-4PH stainless steel and comes with a black oxide coating.  The  FOSSA-762™ can be found online at this link for $120 plus S&H.  This price is consistent with other custom quality muzzle devices.

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-762 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.

Description

  • The FOSSA-762™ 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.
  • It is imperative that a muzzle device on a fighting rifle reduce flash to the lowest possible level. Muzzle flash that is visible to the enemy will draw fire. The brighter the flash the greater the distance it will draw fire from. A compromise on muzzle flash brightness is a compromise on position disclosure. Nothing outperforms the FOSSA-762™ muzzle device when it comes to flash suppression.
  • 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 patented tapered (narrowing) vents which 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-762™ 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-762™ is made from 17-4PH stainless steel with a black oxide surface coating.  The black oxide is a true MIL-DTL-13924 military grade finish.
  • 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.

Features

  • The Most Effective Flash Reduction
  • Mitigated Dust Signature
  • 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-762™
  • SKU: FCX-FHB-762524-002a
  • Caliber: 7.62mm / .30 caliber barrels
  • Thread Size: 5/8" x 24 tpi
  • Material: 17-4PH Stainless Steel
  • Surface Coating: Black Oxide
  • Length: 2.88"
  • Diameter: 0.992"
  • Weight: 5.3 ounces
  • Retail Price: $120

When you purchase a White Sound Defense FOSSA-762™ 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.  Depending on your intended use or preference, you may prefer shims or peel washers, but a crush washer is a quick solution and not that expensive.  The label on the package gives the critical information such as model number (FOSSA-762™), SKU number (FCX-FHB-762524-002a), caliber (.30 / 7.62) and internal threads (5/8" x 24tpi).

Figure 4

These next three photos give you a good look at the ends and top of the FOSSA-762™ Muzzle Device. The device measures 2.88" in length and 0.992" in diameter.  It comes with 7/8" wrench flats at the base for installation.

Figure 5                                               Figure 6                                              Figure 7
   

The FOSSA-762™ Muzzle Device is made from 17-4PH stainless steel and weighed in at 5.3 ounces.  This is significantly heavier than a standard A2 styled muzzle device that comes it at about 2.1 ounces, although I would expect the 5.3 ounces to be closer to other custom devices.

Figure 8

If you take a close look at the muzzle device you will see it is nicely machine and black oxide coated to a dull gray/black appearance.  The internal thread is the standard 5/8 x 24 tpi  (threads per inch) and measured 0.70" deep.  With the FOSSA-762™ installed, you will be adding about 2.25" in length to your rifle.

Figure 9                                                             Figure 10
 

The photo below shows the end of the FOSSA-762™ 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 up direction 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 11

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 other devices 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 to the shooter.

Figure 12


Range Tests

For range testing, I took a look at some different barrel lengths and different calibers (.308 Win & 300 BLK).  The photos below show the FOSSA-762™ installed on my Ruger SR-762 Rifle.  Using this rifle during range testing gave me the opportunity to test the muzzle device on a rifle having a 16.12' barrel and using .308 Win ammunition.  The weight of the rifle without bipod was about 8.5 pounds.

Figure 13

The black oxide finish on the FOSSA-762™ matched that of the barrel perfectly.

Figure 14

This next photo shows shooting this rifle without any muzzle device installed to give you an idea on the amount of flash needing to be suppressed from this rifle.

Figure 15 - .308 Win, 16.12" Barrel, No Flash Suppressor

It is amazing at how well the White Sound Defense FOSSA-762™ muzzle device mitigated the flash of this rifle.  Out of the five shots I took in the dark, I feel the photo below was the most significant flash I was able to catch on video.  If I were to describe the flash, it was more like sparks (unburned powder) flying out the end of the barrel.

Figure 16 - .308 Win, 16.12" Barrel, FOSSA-762 Installed

As a baseline, I compared this to an A2 styled flash suppressor.  The A2 style was also very effective, but seemed to give a consistent red glow around the suppressor with every shot.

Figure 17 - .308 Win, 16.12" Barrel, A2 Styled Flash Suppressor

I also installed the FOSSA-762™ muzzle device on a home built 300 BLK rifle that has a 16" barrel.  Since the FOSSA-762™ is a .30 caliber muzzle device, it could easily be considered as a device for the 300 BLK rifle.

Figure 18

Figure 19

My night video showed that this 300 BLK rifle with a 16" barrel does not produce hardly any flash even without a muzzle device.  The worst flash of 5 shots is shown below.  There was no visible flash when using the FOSSA-762™ or the A2 styled muzzle devices.

Figure 20 - 300 BLK, 16" Barrel, No Muzzle Device

The last firearm that I wanted to evaluate this flash suppression with this muzzle device was another home built 300 BLK pistol that has an 8" barrel.  I'm not sure how many people would choose to install the FOSSA-762 on this platform, but I felt it would be a great way to put the flash reduction feature to the test on a short 300 BLK platform. Please ignore the fact that I haven't selected the type of handguard to use on this pistol yet.

Figure 21

This 300 BLK pistol had an impressive fireball when no suppressor was installed.

Figure 22

Out of the five shots taken on video using the FOSSA-762™, this photo below was the only image with anything visible.  The other four shots were not even noticeable.  I feel this shot was visible only because of the powder spark coming out of the barrel.

Figure 23

With the A2 flash suppressor installed, each shot produced a red glow at the muzzle similar to that shown in the photo below.

Figure 24

For my range tests, I also wanted to try and obtain some objective data for the device's muzzle rise and recoil reducing capabilities.  Just like I did in my review of their FOSSA-556™ device, video seemed to do a good job showing flash reduction, but I struggled with an objective way to show the muzzle rise and recoil reducing characteristics without spending significant dollars in instrumentation.  After brainstorming and feedback from one of my engineering friends, I decided to support the firearm from bungee cords to "float" the firearm and let the video of the firearms movement after firing be an indication of effectiveness.  Although, interpretation of the video is more qualitative, yet I felt it would still give some objective data.

The photo below shows my setup.  The rifle is supported by two bungee cords, one at the front and one at the rear.  The sand bags behind the buttstock are used for evaluating the muzzle rise aspects and with the sand bags remove the rifle could swing similar to a pendulum so I could try and understand recoil reducing aspects.

Figure 25

This next video shows all of my range testing using this setup and the conclusions are summarized below.  In the video I show the recoil of the rifle in both normal speed and slow motion.  I have also tried to place some reference marks in the video so you see the differences in recoil or muzzle rise.  After completing the tests and reviewing all the video (although I only show one shot in each configuration, I shot each three times), I feel next time I will use regular string for the recoil reducing portion so I can get a pure pendulum effect.

Figure 26
 

Range Testing Conclusions:

  • The FOSSA-762™ is very effective in reducing muzzle flash and is superior to the standard A2 style device.
  • Although there may be some benefit, no significant muzzle breaking was observed on an AR-10 style .308 Win rifle.
  • The video shows that the muzzle rise reducing feature was effective on an AR-10 style .308 Win rifle.
  • No flash suppression benefit was observed when using the FOSSA-762™ on a 300 BLK rifle.
  • Flash suppression was very effective on a 300 BLK pistol.
  • No significant difference in muzzle breaking was observed on an AR-15 style 300 BLK rifle
  • No significant difference in muzzle rise reduction was observed on an AR-15 style 300 BLK rifle.

 

Bottom Line:

The White Sound Defense FOSSA-762™ muzzle device does a great job reducing muzzle flash and I believe it is more effective than the standard A2 style flash suppressor when used on a .308 Win rifle.  The FOSSA-762™ also appears to be effective in reducing muzzle rise on a .308 Win rifle, but I wasn't able to see any significant muzzle breaking effect.  When I performed these same tests on a 300 BLK rifle with a 16" barrel, I found there to be no real benefit from installing the FOSSA-762™.  Although, I did find the device to be very effective on a 300 BLK pistol.   I didn't test a 7.62x39 caliber firearm, but I feel the results would be similar to that of the 300 BLK.  If I were considering purchasing the FOSSA-762™, it would be to use on a .308 Win platform rifle which I believe is its intended purpose.


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