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Penn
03-02-2015, 17:32
What does a 5.5" Flash Hinder do for a SBR, other than increase the 11.5" barrel length to 17".

http://www.brownells.com/rifle-parts/barrel-parts/rifle-barrels/ar-15-11-5-w-5-5-fh-5-56-barrel-no-chrome-1-9-sku231000362-69830-142882.aspx?&cm_mmc=external%20partners-_-Second%20Media-_-banner-_-DPMS_barrel

JJ_BPK
03-02-2015, 17:54
Penn

That looks similar to the XM-177 of Nam days. It could be for someone building a retro M16?

I carried one,, it was gently use,, so used it was a smooth bore.. :D

Penn
03-02-2015, 18:07
JJ, understood, but is there an advantage of sound reduction, or any other result related to lengthening a flash hinder, other than accuracy with a longer barrel?

JJ_BPK
03-02-2015, 18:11
JJ, understood, but is there an advantage of sound reduction, or any other result related to lengthening a flash hinder, other than accuracy with a longer barrel?

That is a question I've had for years. It was just a chunk of steel with a bird cage cut on the last inch. Added 6-9 oz?? I know some guys had it taken off and a 1 inch bird cage put on.

The Reaper
03-02-2015, 18:18
JJ, understood, but is there an advantage of sound reduction, or any other result related to lengthening a flash hinder, other than accuracy with a longer barrel?

The sound moderator was first used on the XM177, and it contained internal baffles.

It increased dwell time on the 11.5" barrel to improve reliability, and reduced muzzle blast somewhat.

It is a sound suppressor nonetheless, so it is considered a silencer on a short-barreled automatic rifle.

The current ones out of Brownells are just for looks and don't do anything, to include accuracy, sound, etc., except to make the 11.5" barrel long enough, when permanently attached, to avoid creating a Short Barreled Rifle, which is a Class III weapon required to be on the NFA.

If you were to put an 11.5" barreled upper without a permanently affixed muzzle device of at least enough length to obtain an overall length of 16" or more on a stocked lower, you would be in violation of the NFA and subject to a penalty of ten years confinement and up to a $250,000 fine.

Hope that helps.

TR

Penn
03-02-2015, 18:38
TR, Thank you, your answer directly addressed what I was interested in knowing.

Combat Diver
03-03-2015, 03:29
The 5.5" FH going on a 11.5" bbl would make it legal at 16". There is a .5 overlap for the FH threading on. I used to have one on my first AR build back in 87' to give it that XM177 look. After installing ensure that it's pinned and welded on to keep ATF off your back.

CD

Badger52
07-17-2018, 16:16
I realize this is a necro-post perhaps for this thread but, hey, search engine produced so here comes:

I've seen some "internet shootout" listings of various FH's & their rankings; even one with a guy testing just the retro XM177 FH from Brownell's but by itself.

Understanding the history & TR's succinct explanation of the difference between what was on the real CAR-15/XM177 back in the day, and what the new repop is, I was wondering if anyone has some feedback on the new one and could compare it to your vanilla A2 FH. Just subjective feedback on its capability as a FH, if you happen to have played with both at dusk or at night sometime. Thanks.

JJ_BPK
07-17-2018, 17:28
Can't help with the new'ER FHs, but I did some heavy googling you-tubing several years back for a FH for my Hungarian AMD-65. I built two from kits. The AMD-65 has a 12.5 barrel and came with a fat twin ported chunk of steel that was not long enough to pass mustard for the ATF. So, you had to either build it as a pistol or permanently attach something long enough to make the 16-inch mark.

I chose to build one as a pistol without a FH. The other I use an extension plus the factory FH for the rifle.

At the time there were a bunch of people experimenting for designs in an attempt to hide the flash, none worked very well. The bast was one called the pig.

The engineering problem is the shorter the barrel, the less propellant is burned in the barrel before exit.


pics:

1)IMG_1544 has the original AMD FH

2)IMG_2845
top AMD-65 with aftermarket FH similar to, but long enough to be legal
middle AMD-65 pistol with thread protector
bottom AMD-63 with 45-deg AK slant FH

3)AK AMD-63 (16inch) with original FH at dusk

4)Noveske KX5

5)AMD-65 with x-inch? extention

Net Net, I watch a lot of dusk and after dark FH vids,, some work better than 90% but all have some flash. A suppressor is the best.

Texas_Shooter
07-17-2018, 18:38
I have a KX5 and its worth every penny. It will shoot everything forward and give a substantial flame to boot. Looks good on a SBR build.

Badger52
07-17-2018, 18:42
JJ: Thanks sir. Just kind of curious how good of an actual FH it is (besides the appeal on a retro build). Was the original real one, the "moderator" any better/worse than the birdcage if you recall?

Your shooting pic reminds me of a day years back when at the range playing with new LH-thread AK birdcage & comparing POI's. Later took a late-afternoon walk around the hunting property & finally emerged out of a dense valley, eyes having well-adjusted to the sun that was well below the horizon. Took a poke at a coyote, not realizing I'd left that slant-brake on. Pupils assuredly did not appreciate that. That birdcage went back onto the AK most rikki-tik... lol.

JJ_BPK
07-18-2018, 04:44
JJ: Thanks sir. Just kind of curious how good of an actual FH it is (besides the appeal on a retro build). Was the original real one, the "moderator" any better/worse than the birdcage if you recall?

Your shooting pic reminds me of a day years back when at the range playing with new LH-thread AK birdcage & comparing POI's. Later took a late-afternoon walk around the hunting property & finally emerged out of a dense valley, eyes having well-adjusted to the sun that was well below the horizon. Took a poke at a coyote, not realizing I'd left that slant-brake on. Pupils assuredly did not appreciate that. That birdcage went back onto the AK most rikki-tik... lol.

Can't help with the sound levels or flash of the XM-177 vs m16 vs m60. In 1970 I was a butt-head 1Lt with a platoon of draftees. When I pulled the trigger it, it generally meant we were in deep shiite and I didn't worry about stealth. My real reason for getting the XM-177 was to save weight, so I could carry extra batteries for my RT and extra Claymores. Oz's counted. :lifter

I can say the flash from mine and the other 30-35 troops shooting, was not that bad at night. I was able to maintain most of my night vision, for movement.

Caveat: I was nick-names Scout Hog by my OCS class as I had exceptional nite vision. If you went on MY night movements, NOBODY used lights. I only used the glow if the compass.

There is a FH designed by one of the guys on FAL fora. The idea was the long tines cooled the flash gases. Cooling the hot or unburnt propellant is the key. Those that used it said it was every bit as good as the Hog. He would make the tines as long as you wanted, but most used 2.5 or 4 inch. To me it's just ugly and not practical in the bush.

On the topic of flash, I didn't and still don't put much effort into flash hiding. 1)I don't do nite ambushes anymore. 2)I have cans 3)Never was a sniper

:munchin

Badger52
07-18-2018, 06:16
Thanks for taking time to share the insights.
And your tales. 'Scout Hog' has a nice ring to it. :D

Astronomy
07-18-2018, 12:06
I carried a couple different XM-177s while serving in 2/75 (Old Scroll Pre-Regiment Days).

As previously mentioned, the main purpose of those long "CAR-15" flash hiders was to dampen the fireball that comes with unburnt powder exiting the muzzle of short barrels. For that, they worked pretty well, making the muzzle signature about the same as our more widely issued M16A1s. Between the muzzle device and the flash retardant additives already present in USGI ammo (like M193), muzzle flash was not a problem with the short carbines.

The other thing they did was dampen audible blast a little bit, ensuring that the shorties at least weren't (subjectively speaking) any louder than a standard 20" rifle. My completely unscientific field observations were decibel levels about the same as with an M16A1. I'm sure they were measurably slightly louder under formal lab measuring, but the average rifleman would never notice while outdoors.

While the Feds may have classified the devices as "suppressors", they weren't remotely capable of making a weapon Hollywood quiet. Rather, they just somewhat protected the user from ruptured eardrums. I don't remember them being more loud (or quiet) than an M16A1 with birdcage.

As parts stocks of those repatriated Vietnam War weapons began to wear out (including the long muzzle devices), some of them wound up with armorer/depot replaced A1 birdcages. So equipped, THOSE shorty guns would deafen and blind you.

The 5.5" flash hider was a wartime developmental solution to the pitfalls of early SBR length select fire combat weapons. They weren't there to look cool; they were there to keep ferocious short barrel muzzle blast & fireball to a manageable level. Especially during conduct of full-auto break contact drills. It wasn't there as a nice-to-have option; it was more of a necessity.

When the M4A1 came along, that added length of barrel accomplished pretty much the same thing in a better engineered envelope. Anecdotally, those early 177E1s & E2s (that everyone called "CAR-15s") were mechanically unable to match M16A1 accuracy at distance. The M4A1 with SOCOM profile barrels put paid to that problem and would easily keep up with an A2 out to practical extended ranges. And sometimes surpass 20" A1 performance.

Many of our 177s were shot out when they were delivered to Battalion. One day I was handed a "new" one and went out to zero the gun. It was basically a smoothbore with the slightest remaining traces of lands & grooves. The gun keyholed every single round at 25 meters and would not consistently group all rounds on an E-Type silhouette at that distance. It would literally miss the entire human sized target with some bullets at that range. Needless to say, I immediately DXed it and got a serviceable replacement after wasting a day at the range.

Those guns came to us in a circuitous manner. Left behind in SEA (for allied use), they were captured after S. Vietnam & Laos fell. Then sold (in bulk) by the Communists victors on the world small arms market. Whereupon they were bought back by certain US middleman procurement agents to meet the needs of certain US SOF/Intelligence elements during the late 1970s. Made in the USA, paid for twice, and many of them very hard used across years of combat. Others were nearly pristine (depot warehoused in SEA) and apparently never issued during those conflicts.

I used to reflect upon the likelihood that my Dad's 1967 issued Vietnam weapon wound up in our hands years later. It was entirely within the realm of possibility.

The M4A1s we eventually issued to all SOCOM elements were (and still are) far superior guns in terms of accuracy, reliability, and updated engineering. Too bad we first had to endure a few years of carrying silly-assed interim M16A2s.

Absent a need to routinely mount a can, I have almost zero use for any AR barrel shorter than 14.5 inches (and that length equipped with only a standard A2 birdcage). That length is a good balance of reliable ballistic performance & close quarter dimensional compactness (vehicle employment, CQB, stowage inside of CCW carry containers).

IMHO, the whole need for shorty "compactness" concept is overblown & overwrought. More of a cool factor thing than a usefully practical advantage for most folks. Giving up effective range, velocity, and reliable FMJ fragmentation thresholds simply to gain 2-5 inches of shortened barrel length. Short barrel length gain that often gets partially cancelled out by folks adding after-market longer muzzle devices. Devices that they now really need because the shorter SBR/AR pistol barrels are too short to burn all the powder of 5.56/.223 loads. WTF? Like a snake chasing its tail.

Frankly, most after market flashhiders & muzzle breaks are just fishing lures. Designed to catch fishermen... not fish.

As always...YMMV.

Badger52
07-18-2018, 17:35
Frankly, most after market flashhiders & muzzle breaks are just fishing lures. Designed to catch fishermen... not fish.

As always...YMMV.I get that analogy.

Thanks very much; the subjective info was exactly what I was looking for. I'm not building an SBR or doing a "retro" tribute, was literally just curious. I was out before the A2 came along. I'd agree with you that the M4-like substance got it pretty right for a lot of roles. My carbine is a delight in the bush & the 16" midlength w/ACOG shoots pretty well too, both happily digest my M193 and handle just fine. ('Course I'm not hanging a ton of HSLD light-weight stuff on 'em either.)

Thanks again.