FAQ: Your Slot Brake kind of looks like a flash hider. Does it hide flash?

Sparrow Dynamics
5 min readApr 29, 2024

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Sparrow Dynamics Slot Muzzle Brake

Our Sparrow Dynamics Slot Brake was designed to mimic the aesthetics of a flash hider, BUT function solely as a muzzle brake. We also manufacture a very effective Slot Flash Hider if hiding flash is what you are looking for.

Flash hiders / flash suppressors typically have a large exit hole and tines or linear lines cut into the sides, sometimes many small holes drilled into the sides with a large exit hole. Muzzle brakes that do not hide flash will have large side ports and a small bullet sized exit hole and with no tines on the front to disperse blast.

How Muzzle Brakes Function:

The small exit hole gets blocked by the bullet for a moment and traps expanding gasses behind it that must escape through the slot ports. Some of those gasses as they are moving forward hit the inside front edge of the port and push the rifle forward to counteract the recoil. This is how typical muzzle brakes function.

Typical Muzzle Brake Gas Flow
Typical Muzzle Brake Gas Flow (Top Section View)

The bullet trapping the gasses for a moment usually causes the occasional very big flash due to the rapid expanding gasses and unburnt powder. But this typical geometry also results in much of the concussive blast heading back toward the shooter and anyone standing to the sides. Therefore typical muzzle brakes can be uncomfortable to shoot, especially at indoor or covered ranges. Customers have been expressing this issue to us for years and we listened.

Our Solution:

Our Slot Brake geometry is different and eliminates the discomfort from the concussive blast. It does not reduce any sound, but it “feels” quieter to the shooter and to anyone standing to the sides. It has more of a thump sound that is heard and not felt. It achieves this with the ramped ports and the front conical crown. The gasses get trapped by the bullet in the small exit hole and expand rapidly. The gasses hit the ramp in the front of the slot shaped port and smoothly deflect forward and to the side, rather than back. This pushes the rifle forward to counteract some recoil. The bullet trapping the gasses for a moment usually causes the occasional very big flash due to the rapid expanding gasses and unburnt powder.

Sparrow Dynamics Slot Brake Gas Flow
Sparrow Dynamics Slot Brake Gas Flow (Top Section View)

If you are asking this question because you are building a featureless rifle in California (helpful legal info here), then you should read the current California DOJ definition for flash hider before looking at the test photos below.

Current definition per the California Code of Regulations, Title 11, Division 5, Chapter 39 Assault Weapons and Large-Capacity Magazines, Article 2, § 5471, (r) “Flash suppressor” means any device attached to the end of the barrel, that is designed, intended, or functions to perceptibly reduce or redirect muzzle flash from the shooter’s field of vision. A hybrid device that has either advertised flash suppressing properties or functionally has flash suppressing properties would be deemed a flash suppressor. A device labeled or identified by its manufacturer as a flash hider would be deemed a flash suppressor.

The important part to get out of that definition is “functions to perceptibly reduce or redirect muzzle flash from the shooter’s field of vision”. So “shooter’s field of vision” and “perceptibly reduce” is what we will focus on in the paragraphs below.

In this first set of photos, we see a giant muzzle flash due to the rapid expansion of gasses and unburnt powder getting ignited. This happens occasionally with our Slot Brake and with all typical muzzle brakes. This image alone shows that our Slot Brake is not a flash hider according to the CA DOJ definition.

This second set of photos shows what some other shots look like using our Slot Brake. In other words, not every shot produces a large muzzle flash. This shows a dimmer, but still large flash up into the “shooter’s field of vision”. BUT, notice that this photo what taken from above the shooter’s eye. The camera should have been moved lower to properly show the “shooter’s field of vision”. You can see in the second photo that the blast does move up into the “shooter’s field of vision” due to the top slot ports.

This third set of photos shows the same rifle being shot with the same ammunition, but using our Barrel Thread Protector instead of the Slot Brake. It shows that the flash is fairly small and round. There is a brighter spot in the center of the flash. Notice that there is no flash that moves up into the “shooter’s field of vision”. BUT, again, this photo what taken from above the shooter’s eye. The camera should have been moved lower to properly show the “shooter’s field of vision”. And if it was lower, the bright center would be completely blocked by the front of the rifle. So comparing this to the shot above, the shooter perceives a brighter flash with our Slot Brake because the flash moves up into the “shooter’s field of vision”. But none of this really matters legally, because occasionally the muzzle flash is very big and bright as in the first set of photos.

Summary:

Our Slot Brake does not function as a flash hider in general OR according to the CA DOJ definition. This is a great option if you are building a featureless rifle in CA, or if you just want the recoil reduction benefits of a muzzle brake, but without the uncomfortable concussive blast that usually comes with a brake.

If you are looking for an awesome flash hider, check out our Sparrow Dynamics Slot Flash Hider. If you are looking for the typical ported muzzle brake that practically eliminates recoil, check out our 3 port Muzzle Brake.

Please visit our website and contact us if you have any questions. We are happy to help!

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