It started when I was looking for a replacement for the plain M16A2 flash hider, already on millions of weapons, including my snazzy new Bushmaster ACR. I didn't expect much of a difference in performance, but I was surprised that SureFire, maker of high-tech flashlights, was now making sound suppressors, and the muzzle attachments to optimize them.
A little bit of reading advertising copy told me that these "simple" devices can reduce flash, reduce recoil, and redirect noise and muzzle blast, depending on your needs, and the particular design. As usual, engineering compromises are involved, some work better than others, prices are MSRP, and your mileage may vary.
The story begins with the fireball of hypersonic gas that's pushing the spinning bullet down the barrel, while trying to get past the "slow moving" bullet at the same time. There's a column of hot gas ahead of the bullet, and even hotter gas behind it. Once the bullet has cleared the muzzle, all of this gas is a hindrance to ballistic performance. It would be best if the bullet could sail through "clean" air, but there's this blazing turbulence behind it, trying to mess things up.
Of course, this hot gas cools quickly, and slows down until it can no longer degrade bullet performance. But until then, it's best to minimize its degrading performance on the projectile, and the entire weapon.
The first order of business is to divert as much of the hot gas as possible away from the bullet. An expansion chamber gives some of the gas a path away from the base of the bullet, and sends it into a direction where it will do less harm. Then comes vents to encourage the hot gas to go somewhere else. Or channels to pipe the hot gas exactly where you want it. Finally, if you still need to suppress muzzle flash, some sort of diffuser fins on the front to break up what's left of the gas column, and send the pieces into different directions so they can cool faster, and not become visible.
That's the mission statement of a modern muzzle "device". Add a noise suppressor over that if you want to mechanically delay the gas column, and encourage the transfer of heat energy from the gas to the metal and baffles of the can.
I have nothing but my own hunch to go on, but I believe the proliferation of sound suppressors during this war has encouraged a number of suppressor designs, plus muzzle "brakes" to go with them, or used standalone. Enhanced optics became common in this war, and I think suppressors, while not exactly common, are available through the supply chain without too much red tape.
While researching this, I realized I have a bunch of "flash hiders" that were "auditioned" for my various rifles, along with the "winners" that are presently affixed.
Here are some of the "new breed" on some rifles. I'm sure some version of the M16A2 flash hider would still work fine, but I wanted to "pimp my piece" a bit, and maybe get better performance, too.
One the left is a Primary Weapons System flash hider on the DPMS "AR10". Large ports on the side dump gas from the expansion chamber, and little horizontal fins provide a bit of control over muzzle rise. Four off-axis fins in front do their bit for hiding flash. I haven't fired it yet, but this muzzle device, intended to be used with a suppressor, would reduce recoil and flash. Noise, OTOH, would probably be uncomfortable to shooters on either side.
In the middle is a Vltor flash hider on the Sig P556. It has an expansion chamber and flutes at two levels on the side to disperse flash. Again, not yet tested.
Finally, the SureFire flash hider, designed to be used with one of their suppressors. An expansion chamber and angled flutes make it an effective flash suppressor. I have fired this one, and it seems to be a bit louder than other designs, but that's just my seat-of-the-pants impression.
The M1A SOCOM requires a customized flash hider due to the non-standard threads on the short 16-inch barrel.
At the bottom is the factory version, set up with lots of small holes for recoil reduction. Since I've only fired it outdoors, I really have no idea about muzzle blast and flash, although it was pleasant to shoot. I think someone else at the indoor range had a SOCOM, and indoors it does not seem very bystander-friendly.
Above that is the Smith Enterprises version, which allows interchanging the classic Smith "spiral finger" flash hider, or a similar one with most of the "fingers" closed off, except for some outlet jets. It hasn't been tested yet, either.
At the top is another PWS flash hider. You get a better view of some of the porting, and the flash hider "fingers".
Finally, some unused 5.56mm flash hiders that sorta accumulated like lint in the corners of my parts boxes. Some have been used on a weapon, the others are just sitting around for their big chance.
From the left, a standard M16A2, which seems to come on almost every brand of rile. Next, the classic Smith "four fingers". Third is a Vang CQB "flash hider". This is a special design, used mostly in gunfights in living rooms or phone booths. A large conical expansion chamber feeds six exhausts that are arranged in a circle around the central bullet exit. The theory is to throw all the muzzle blast and flash at the target, along with the bullet. The bad guy already knows you're there, so why bother to hide anything? Also, it prevents friendlies on either side of you from getting hit with the blast.
The same concept is used on the Noveske "flaming pig" CQB flash hider. A vey large expansion chamber leads to a "rocket nozzle" in the front. The idea is to let the bullet leave while the hot gas is still bouncing around inside, looking for the exit hole. The instructions warn that, under heavy use, some unburned powder may accumulate until one shot lights it off, shooting a several-foot-long flame. The "flaming pig" logo is optional, depending on your opinion of your enemy's opinion of pork products.
Flash hider number 5 is what I call the "dial-a-blast" CQB from Primary Weapons Systems. The inner part consists of a tapered post with two long slots in it. The outer shell is threaded so you can move the exhaust holes directly over the inner slots, or more toward the rear, where there is a narrower path for the gas to find the exhaust holes. This is one design I'd really like to try out on a crowded indoor range.
Number 6 is a Troy Industries design, with three squiggly slots for hiding the flash, and a vey sharp front end for jabbing people without doing too much damage to them. Next to that is a shorter PWS flash hider/brake. I was going to use it on the P556, but the front "fingers" always got hung up on the PALS loops when I tried to put it into the case, so I went with something with a closed ring in front.
The last two are a bit of a mystery to me, in that I don't remember off the top of my head who makes them, or even how I got them. They may have been "take offs" for some muzzle brake project I did for someone else.
So you see, the simple slotted flash hider from the M16A2 has evolved into many designs trying to balance recoil, noise, and flash reduction with optimal performance with one brand of suppressor or another. And for every design that drops by the wayside, we'll probably see two new ones appear. All of this is to assure the enemy that the bullet with his name on it is given the best possible start on its flight.