XM-177 Type flash hiders ... do they work?

[TonyAngel]

I'm considering pinning and welding a 12.5" barrel to 16" and plan to use one of the long xm177 looking flash hiders. Do these muzzle devices actually work as a flash hider or are they purely for aesthetic purposes?

Please don't post about how stupid it is to pin and weld a 12.5" barrel. I have a 12.5 criterion barrel that shoots very sub MOA, wasn't cheap and wasn't easy to find, so I'm just preparing just in case.

 

[Robbins290]

I throw on a 16" rifle once, seemed to work good. also tried it as a joke on a 9mm and 357 sig pistol. ALSO worked good.

 

[gotboostvr]

The original ones are considered suppressors.

The faux XM177 moderators should work pretty well as a flash hider depending on how the inside of it is set up. I think some are better than others, but by virtue of being a large expansion chamber they should work pretty well.

 

[TonyAngel]

The original ones are considered suppressors.

The faux XM177 moderators should work pretty well as a flash hider depending on how the inside of it is set up. I think some are better than others, but by virtue of being a large expansion chamber they should work pretty well.

Do you happen to know of a specific one that works better than the others?

The one I'm considering is the KAK extended A2 because they specifically say that it will bring a 12.5 to 16.

 

[gotboostvr]

Do you happen to know of a specific one that works better than the others?

The one I'm considering is the KAK extended A2 because they specifically say that it will bring a 12.5 to 16.

That I cannot say. My plan for a retro build is a 16" barrel with one of the faux moderators that extend back over the barrel so I can just unscrew it and put my actual suppressor in when wanted.

 

[TonyAngel]

At this point, I see two candidates. The first is the KAK model that is good for any caliber up to 9mm and the other is the one from brownells that is .22 caliber specific. I'm also guessing that the KAK will be lighter assuming like diameters.

I'm thinking that the one reamed for up to 9mm may do a better job of suppressing flash due to being more reamed out therefor having a larger expansion chamber. Am I wrong?

Or are there going to be trade offs due to one being caliber specific?

 

[FL-NC]

The ones that are available on the open market don't do a thing to eliminate flash in my opinion. US mil ammo also has a flash retardant in the powder, BTW. The original ones were called "moderators". For some reason, the gov't has ruled them to be suppressors, I guess because they have some baffles in them. It was explained to me the baffles were to produce some back pressure and make those old CAR15 type guns cycle more reliably. I don't see the point of this, since none of my carbines I used (between 10" and 14.5") had issues cycling with any issue ammo I ever used. I have been around some of these original type 177 FH dealios being fired. If they are suppressors, they are the Edsel of suppressors cause they are really loud- like any 5.56 not going through a "real" suppressor.

 

[CapnMac]

From memory, there was an expansion chamber behind the ports, and area of enlarged diameter.

AFTE decided that might reduce the sound signature (if only 5-6 dB) and that was reason enough to ban them.

Now, all the ones I have seen were basically bore diameter the whole length, with A1 flash holes at the terminal end.

All the "clone builds" I have seen had no reduction in flash.

 

[BigBlue 94]

Two xm177 threads in one day!?

I put one, from maybe brownells, DSA, or Delta Team Tactical, on a 10.5" barrel. I had to weld a half inch of stock to the threaded end to get me to 16". Mine is welded right to the barrel. It is nothing more than a long flash hider. No chamber at all. Just a big hollow tube with A1 flash cuts at the end.

Original moderators are NFA items. They muffle the report by just a few dBs. Their purpose was to make the short barreled GAU-5A rifles sound like a regular M16A1. The VC knew that MacV-Sog was using short barreled carbines so it was a matter of deception.
My GAU-5A/A clone (pre extension and welding, on a different lower)

And the extension up close. I ditched the grenade ring when i welded it to the barrel.

It is going on an A2 lower with the correct 2 position collapsing stock. I just finished painting it Colt Gray on monday and am going to assemble it finally tomorrow. The whole build was due to me coming across an original SinglePoint OEG like used all the way back in 1970 in Son Tay.

 

[js8588]

By pinning and welding you might change your barrel harmonics enough to make it shoot less accurately.

Take the "form 1 amnesty" and just roll on with it as its built. But with a stock.

 

[derek45]

The original were suppressors, designed to bring the sound down to the level of a 20" M16

with use, they accumulated fouling, which made them not work as well ( louder)

Source = THE BLACK RIFE By E.C. Ezell

 

[entropy]

The ones that are available on the open market don't do a thing to eliminate flash in my opinion. US mil ammo also has a flash retardant in the powder, BTW. The original ones were called "moderators". For some reason, the gov't has ruled them to be suppressors, I guess because they have some baffles in them. It was explained to me the baffles were to produce some back pressure and make those old CAR15 type guns cycle more reliably. I don't see the point of this, since none of my carbines I used (between 10" and 14.5") had issues cycling with any issue ammo I ever used. I have been around some of these original type 177 FH dealios being fired. If they are suppressors, they are the Edsel of suppressors cause they are really loud- like any 5.56 not going through a "real" suppressor.

The point is back then, the CAR/XM177E2 used the gas tubes from the M16, just cut down to fit. This seriously over gassed the shortys. Between the XM177E2 and the M4, we solved this with the 10" commercial barrels the recon unit in the 7thID(L) bought to put on their A2 lowers by making "pigtails", carefully bending gas tubes to fit under the carbine length handguard. The M4's gas tube's ID was changed for better cycling.

 

[BigBlue 94]

For reference, the inside of my XM-177 flash hider

 

[brass shower]

The 5.5” flash hiders are more barrel extensions than hiders. They may mute the muzzle flash to an extent versus a bare muzzle but they aren’t as effective as a real flash hider.

Unburned power exiting the muzzle mixes with oxygen in the air to burn causing a brighter flash. One way to stop an oxidation reaction is to add more fuel or more oxidizer to the reaction. Flash hiders work by forcing jets of unburned power through the slits into the atmosphere to increase the oxidizer portion of the reaction, thus reducing the flash signature. When using the 5.5” “hider” the hollow portion of the device acts more like a mixing bowl for the fuel and oxygen to mix, resulting in little if any flash suppression, though there may be a flash and blast reduction simply from having the conflagration exiting to the atmosphere 5” further away from your face.

Somewhat related, The “first round pop” in sound suppressors is due to oxygen in the can mixing with unburned powder and burning. When the shooting string stops, oxygen from the atmosphere gradually re-enters the can and the pop will be heard again when resuming fire.

 

[lysanderxiii]

That is NOT what causes muzzle flash.

And, that is NOT how a flash suppressor works.

There are three types of muzzle flash: muzzle glow, primary, and secondary. Muzzle glow and primary flash are just the incandescence of the hot waste gas and are actually rather dim in comparison to the secondary flash. Unless the barrel is extremely short, less than 7 to 8 inches for a rifle like a .308 Winchester, all the propellant is burnt long before the bullet exists the muzzle.

The primary flash is just the glow of the super heated gas as it exits the muzzle

For secondary flash: The combustion products of burning propellant are inflammable, they just need oxygen and an ignition source. When these gases leave the muzzle at high pressure, 4,000 to 12,000 psi and high temperature, 1300 to 2000 R, they expand adiabatically down to low pressure and temperature, actually over expanding far below atmospheric conditions until a normal shock wave sets in. Across the shock wave the pressures and temperatures rise again to the muzzle exit conditions. Within this region of the shock wave there is a large amount of turbulence which mixes ambient air with the propellant waste gas. Now in the area of the shock wave we have the three things needed for combustion, fuel, air and a heat source, so you get a nice ball of flame. If you look closely at a muzzle flash, you will note that it is always separated from the muzzle by some distance.



The way a flash hider/flash suppressor works is to prevent the shock wave from forming, or reduce the intensity of the shock wave to minimize the temperature rise. The best way to do that is to absorb energy from the muzzle gas through making it move the tines of a prong, duck-bill, or cage type flash hider. The other type is the cone type flash hinder which works by controlling the expansion of the gas, the can (WW2 BAR) type is a less effective version of the cone. The M16 cage-type flash hider is actually a combination of both the cone and tine types and very effective.

 

[N555]

The original were suppressors, designed to bring the sound down to the level of a 20" M16

with use, they accumulated fouling, which made them not work as well ( louder)

Source = THE BLACK RIFE By E.C. Ezell

View attachment 1101518

View attachment 1101519

View attachment 1101520

Innovative industries sells them for $269, I have one in NFA jail right now.

 

[lysanderxiii]

The point is back then, the CAR/XM177E2 used the gas tubes from the M16, just cut down to fit. This seriously over gassed the shortys. Between the XM177E2 and the M4, we solved this with the 10" commercial barrels the recon unit in the 7thID(L) bought to put on their A2 lowers by making "pigtails", carefully bending gas tubes to fit under the carbine length handguard. The M4's gas tube's ID was changed for better cycling.

The M4's gas tube is the same diameter, both inside and outside, as the M16 gas tube. Both use 304 stainless steel, 1/2 hard, 0.187 +.005 OD, 0.0350 +/- .0055 wall thickness. (Although in 1987, 321 stainless steel was added as an alternate.)

The allowable range for the I.D. is 0.1465 to 0.1625 inch, and has always been this.

 

[tommy.duncan]

That is NOT what causes muzzle flash.

And, that is NOT how a flash suppressor works.

There are three types of muzzle flash: muzzle glow, primary, and secondary. Muzzle glow and primary flash are just the incandescence of the hot waste gas and are actually rather dim in comparison to the secondary flash. Unless the barrel is extremely short, less than 7 to 8 inches for a rifle like a .308 Winchester, all the propellant is burnt long before the bullet exists the muzzle.

The primary flash is just the glow of the super heated gas as it exits the muzzle

For secondary flash: The combustion products of burning propellant are inflammable, they just need oxygen and an ignition source. When these gases leave the muzzle at high pressure, 4,000 to 12,000 psi and high temperature, 1300 to 2000 R, they expand adiabatically down to low pressure and temperature, actually over expanding far below atmospheric conditions until a normal shock wave sets in. Across the shock wave the pressures and temperatures rise again to the muzzle exit conditions. Within this region of the shock wave there is a large amount of turbulence which mixes ambient air with the propellant waste gas. Now in the area of the shock wave we have the three things needed for combustion, fuel, air and a heat source, so you get a nice ball of flame. If you look closely at a muzzle flash, you will note that it is always separated from the muzzle by some distance.

View attachment 1102436

The way a flash hider/flash suppressor works is to prevent the shock wave from forming, or reduce the intensity of the shock wave to minimize the temperature rise. The best way to do that is to absorb energy from the muzzle gas through making it move the tines of a prong, duck-bill, or cage type flash hider. The other type is the cone type flash hinder which works by controlling the expansion of the gas, the can (WW2 BAR) type is a less effective version of the cone. The M16 cage-type flash hider is actually a combination of both the cone and tine types and very effective.

View attachment 1102437

Brother!! That is a Bad A$$ picture!!
Great post and description too!!

 

[brass shower]

@lysanderxiii thanks for correcting my over-simplified incomplete explaination. I learned something new today!

 

[David Hoback]

lysanderxiii: Good response & explanation. Although Brass Shower’s response is a simplified version. It’s quite easy to look up exactly “How” a Flash Hider works. And he DID speak correctly of the XM-177. From my experience, they never did work very well. Still typically a HUGE fire ball coming from them. I’ve used Surefire 3p Flash Hiders for 6 or 7 years. They are among the top performers with hardly even a spark coming from the muzzle in complete darkness. I actually just switched to Surefire Warcomp, which is still a 3-prong hider…just with a few ports for a bit of compensation.

 

[lysanderxiii]

Although I Brass Shower’s response simply a simplified version.

What he wrote:

"Unburned power exiting the muzzle mixes with oxygen in the air to burn causing a brighter flash. One way to stop an oxidation reaction is to add more fuel or more oxidizer to the reaction."

First off, if there is any unburnt propellant, it can burn quite well without mixing atmospheric oxygen. Propellant is a self contained energy source, it has its own oxidizer and fuel, so in can burn in a vacuum if necessary.

The persistent myth that muzzle flash is from unburnt propellant is wrong and people need to stop repeating it.



The second sentence, while technically correct, has nothing to do with muzzle flash suppression. As noted, propellant carries its own oxygen, so the fuel-oxygen ratio cannot be changed. And if this statement was directed at the combustible waste products of the propellant combustion, the oxygen mass require to get the fuel-oxygen mix outside the combustible region would be a few pounds of atmospheric air, significantly more than the slight draft through the flash hider slots.

 

[brass shower]

It’s all good, correcting misinformation is not a personal attack. I perceived no flame (ha).​

 

[David Hoback]

The persistent myth that muzzle flash is from unburnt propellant is wrong and people need to stop repeating it.

Yes, Bill Nye the Science Guy. You are correct on that. Some of us know these things, some don’t & some say it in simple terms which aren’t necessarily correct as it pertains to Physics, but still gets the message across AS it pertains to the subject material of the Thread. I certainly don’t believe it’s leading new Firearms owners down a dark & unforgiving path.. What I envision when reading your words; having the perception of Impending Doom & “Dire Consequences”

I think things will be ok.

If you would would like to have a discussion of the false narratives handed down from one generation to the other, many false beliefs which have risen to almost “Cult Like” status in the Firearms community as a whole… well I’m all in. Just create another thread.

However, I’m curious..do you have anything to add to the actual subject at hand, the XM-177?

 

[N555]

Shold be easy enough to test right?
Fire gun, see how big muzzle flash is.
Put gun in a box, remove all air from box and retest, preferably with a see through box.
Skip to about 2:20

 

[Choctaw]

I have one on a carbine and it works great. I haven't experienced the horrendous fireball others have mentioned.

I have two carbines with pinned and welded barrels: One is a PSA and the other a BCM Recce 14. I haven't noticed a loss of accuracy in either. I'm not a fan of putting myself under further government restrictions so I'm happy with my choices.