View Full Version : What's the history behind the moderator?
What was the actual line of reasoning behind the moderators on the early carbines? I get that they help with cycling, but why didn't they just 86 the moderator and replace it with an equal amount of additional barrel length? I'm also not clear on why they were necessary in the first place. Our 10 inch carbines work just fine today, and I'm not seeing any obvious reasons why they shouldn't have worked just as well sans moderator back then.
I could be wrong here, but I read somewhere (Blackrifle book?) that it was used to cut the muzzle blast down to a 20" rifle. I don't remember reading that they did it to make it cycle properly. It's been years since I've looked into any of this, so again I could be off base here.
Part of it had to do with muzzle report as well. As far as make it sound more like an AK.
That’s what been said all over the inter webs anyway.
ETA: Which I always thought was funny.
To me all firearm reports sound very similar. Especially at distance.
If it were a machine gun and shooting full auto - I could so cyclic rate being an indicator. But, I don’t think that I remember that ever being cited. It was always that the gun report sounded more like an AK.
God Bless,
Brandon
Eurodriver
03-04-21, 17:05
Part of it had to do with muzzle report as well. As far as make it sound more like an AK.
That’s what been said all over the inter webs anyway.
ETA: Which I always thought was funny.
To me all firearm reports sound very similar. Especially at distance.
If it were a machine gun and shooting full auto - I could so cyclic rate being an indicator. But, I don’t think that I remember that ever being cited. It was always that the gun report sounded more like an AK.
God Bless,
Brandon
Yeah I’ve been around guns all my life, even professionally, and from 1/2 mile away I wouldn’t be able to tell you if the gun was a bolt rifle or an AR15 or an AK.
Don’t want to drift the thread but I’d be curious if there are people who can. Hell I can barely tell the difference between a handgun and a rifle if it’s shot into a close berm. The only tell for me is loud magnum rifles or a sonic boom that last for 5 seconds (usually when a hunter misses a deer lol)
why didn't they just 86 the moderator and replace it with an equal amount of additional barrel length?
Excellent question. Rob the cartridge of a bunch of velocity, but still have the additional length? Completely irrational.
Yeah I’ve been around guns all my life, even professionally, and from 1/2 mile away I wouldn’t be able to tell you if the gun was a bolt rifle or an AR15 or an AK.
Don’t want to drift the thread but I’d be curious if there are people who can. Hell I can barely tell the difference between a handgun and a rifle if it’s shot into a close berm. The only tell for me is loud magnum rifles or a sonic boom that last for 5 seconds (usually when a hunter misses a deer lol)
IIRC you were in Iraq, correct? I'll assume the distances were closer than 1/2 mile. Could you tell an AK at "combat distance"? I think in Vietnam the ranges were close in the jungle and maybe (?) it was more discernable from an M16. I've heard and read 'Nam vets saying that some guys would pick up an AK but you had to be careful because in that environment (i.e. not much of a clear line-of-sight) you could be mistaken for an NVA or VC and shot at by your fellow Americans.
Excellent question. Rob the cartridge of a bunch of velocity, but still have the additional length? Completely irrational.
True, but the comment about making the report like that of a 20" M16 I've heard before. Assuming that is fact, adding additional barrel length would help ballistics-wise but would indeed still sound louder than an M16.
Not sure if it was meant as a ruse to make the enemy think they were engaging a larger, better armed regular infantry unit as opposed to a six man LRRP or SOG team. I have read where some of those type of teams would load their first few mags with all tracers to make it appear that the enemy was engaging a larger unit. I guess every little bit of advantage in those life-or-death situations helps.
turnburglar
03-04-21, 21:06
I think when they say "sound" more like an AK, they are looking at it from a total signature perspective. Think about it this way: the flash from a 11.5 AR would be pretty significant compared to a 16" AK. The longer and larger bore allows the AK to simply burn more powder. I also remember hearing that the actual moderators had baffles in them and would be classified as a NFA item by todays standards. The baffles and length of the device would give the short AR a more tame muzzle signature. In the jungles of 'Nam the SOG dudes would have been operating a lot in low light and no light. A short barrel AR would have very different signature from an AK in that kinda environment.
1_click_off
03-04-21, 22:13
Googling after reading the posts above and came across this site. https://retrorifles.com/moderator-flash-hiders-car-15-xm177e1-xm177e2-colt-commando-1963-1974/ Looks like they have some neat gear and appears to be in stock.
I think when they say "sound" more like an AK, they are looking at it from a total signature perspective. Think about it this way: the flash from a 11.5 AR would be pretty significant compared to a 16" AK. The longer and larger bore allows the AK to simply burn more powder. I also remember hearing that the actual moderators had baffles in them and would be classified as a NFA item by todays standards. The baffles and length of the device would give the short AR a more tame muzzle signature. In the jungles of 'Nam the SOG dudes would have been operating a lot in low light and no light. A short barrel AR would have very different signature from an AK in that kinda environment.
They have in recent history been reclassified as suppressors, but only because they barely fit the loose definition of one legally speaking. The sound reduction isn't appreciable, but since it's measurable, that's enough for the ATF to go after them. They have very little volume and no baffles whatsoever. Just a diffuser tube with several expansion chambers.
I don't know about the flash suppression, but I don't think they would be particularly effective at that either. Just guessing here, but I think that same length of additional barrel would be just as effective because it would allow more powder to burn. So I think in those terms it would be a draw between the 10 inch barrel with moderator and an M4. Contrary to popular belief, suppressors aren't all that great at flash suppression.
I am really surprised though that someone didn't say hey let's make this thing a little bigger and put real baffles in it. Actual suppressors of that length are very effective. I have a little k can on my Mk18 upper that does a really good job. It's not hearing safe by any means, but it's close. I've fired a few rounds without ear pro before to hear what it sounds like, and it was slightly uncomfortable, but not painful like it would be sans suppressor.
I read elsewhere (I donÂ’t remember where) that the moderator, like a suppressor, was designed to increase the back pressure & change the pressure curve.
I saw Ian McCullen on Forgotten Weapons make the claim about making the CAR sound more like an AK but have never seen that written anywhere. IsnÂ’t the cyclic rate of the carbines higher than an AK?
The lack of written sources makes moderators a perfect “urban legend.” A roommate of mine back in the early 1980s was in the Army 1978-83 & he had said the moderators were just to turn the muzzle blast into “tolerable” from “ear-splitting/ear-bleeding.” He also described some of the rifles having the older “pig tail” gas tubes, so as I piece this together, it sounds like a working experiment to address some of the carbine cycling issues, is all.
But I freely admit this is retrospective speculation. It would seem an Army Training Manual on the XM177E2 would address the moderator? Or some other manual.
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I read elsewhere (I donÂ’t remember where) that the moderator, like a suppressor, was designed to increase the back pressure & change the pressure curve.
I saw Ian McCullen on Forgotten Weapons make the claim about making the CAR sound more like an AK but have never seen that written anywhere. IsnÂ’t the cyclic rate of the carbines higher than an AK?
The lack of written sources makes moderators a perfect “urban legend.” A roommate of mine back in the early 1980s was in the Army 1978-83 & he had said the moderators were just to turn the muzzle blast into “tolerable” from “ear-splitting/ear-bleeding.” He also described some of the rifles having the older “pig tail” gas tubes, so as I piece this together, it sounds like a working experiment to address some of the carbine cycling issues, is all.
But I freely admit this is retrospective speculation. It would seem an Army Training Manual on the XM177E2 would address the moderator? Or some other manual.
Ding Ding, As I understand it's this as they were still working on the gas porting, etc.
Time travel back to 1968, Army 'we want a M16 as short as possible as fast as possible" Colt "here's one with a 10" barrel" Army "this thing ain't as reliable as a 20" and it's really flashy and loud" Colt "here this muzzle thingy fixes that" Army "that's better" Colt "hey we fixed that reliability issue by adding 1.5" to the barrel, still want that muzzle thingy" Army "sure why not". Colt "one day there will be an internet and geeks will obsess over why we did this, should we document our reasoning?" Army "f em we've got a war to fight".
Time travel back to 1968, Army 'we want a M16 as short as possible as fast as possible" Colt "here's one with a 10" barrel" Army "this thing ain't as reliable as a 20" and it's really flashy and loud" Colt "here this muzzle thingy fixes that" Army "that's better" Colt "hey we fixed that reliability issue by adding 1.5" to the barrel, still want that muzzle thingy" Army "sure why not". Colt "one day there will be an internet and geeks will obsess over why we did this, should we document our reasoning?" Army "f em we've got a war to fight".
Yes, that was the other thing: cyclic rate. My roommate said it was like 900rpm & would frequently jam, but they were fun when they didn’t jam, until the next jam, hence the pigtail & moderator. Not sure what else was “tweaked” but Hbuffers didn’t exist then.
He said nobody wanted to carry them, due to reliability issues.
Yes, that was the other thing: cyclic rate. My roommate said it was like 900rpm & would frequently jam, but they were fun when they didn’t jam, until the next jam, hence the pigtail & moderator. Not sure what else was “tweaked” but Hbuffers didn’t exist then.
He said nobody wanted to carry them, due to reliability issues.
SOG guys swore by them. Also, I don't recall anything about pigtail gas tubes. Not trying to be argumentative, just stating what I've read.
Yes, that was the other thing: cyclic rate. My roommate said it was like 900rpm & would frequently jam, but they were fun when they didn’t jam, until the next jam, hence the pigtail & moderator. Not sure what else was “tweaked” but Hbuffers didn’t exist then.
He said nobody wanted to carry them, due to reliability issues.
Wouldn't the moderator actually increase cyclic rate?
Time travel back to 1968, Army 'we want a M16 as short as possible as fast as possible" Colt "here's one with a 10" barrel" Army "this thing ain't as reliable as a 20" and it's really flashy and loud" Colt "here this muzzle thingy fixes that" Army "that's better" Colt "hey we fixed that reliability issue by adding 1.5" to the barrel, still want that muzzle thingy" Army "sure why not". Colt "one day there will be an internet and geeks will obsess over why we did this, should we document our reasoning?" Army "f em we've got a war to fight".
They did document it. See "Final Report of Engineering Design Test of Modified Flash Suppressor for CAR-15 Submachine Gun" and "Product Improvement Test of Submachine Gun, 5.56mm, XM177E2"
The extra 1.5 inch barrel length was so it could fit the XM148 Grenade launcher. The new flash hider to control the objectionable flash and noise, however, noise was still considered objectionable, even with the new suppressor. (The term "moderator" is not used in official documents.)
However, the new flash hider/suppressor created bigger problems than it solved. M196 tracer had extreme yaw and erratic flight when fired through the longer flash hider, M193 also showed this tendency but less extreme. Both ammunition types were considered insufficiently accurate through the XM177E2. The interior of the flash hider fouled and was difficult to clean. Also, the XM177E2 did not show acceptable reliability at low temperatures.
They did eventually drop the long flash hider for a slightly longer barrel to improve reliability, you might know it as the M4 Carbine.
So the question I have is why does my 10.3 Crane spec barrel run fine without a moderator and without exhibiting the issues of the XM177. Not trying to be smart ass, but my upper isn't sprinkled with magic fairy dust. Physics haven't changed. What makes the difference? I usually run a can on it, but it runs without just fine. In fact I think .070 is a bit overgassed.
So the question I have is why does my 10.3 Crane spec barrel run fine without a moderator and without exhibiting the issues of the XM177. Not trying to be smart ass, but my upper isn't sprinkled with magic fairy dust. Physics haven't changed. What makes the difference? I usually run a can on it, but it runs without just fine. In fact I think .070 is a bit overgassed.
You're talking about 50+ years ago. They didn't have the experience we have nowadays tinkering with gas port sizes, buffer weights, etc. You gotta figure the M4 is nearly a 100% issued weapon at this point (for all services), and has been around for 30 years. The XM177 guns were a distinct minority at the time and relatively new.
Have to laugh though, because now we have the thoroughly de-bugged M4 Carbine but some HSLD units went [back] to a shorter 10.3" barrel again!
So the question I have is why does my 10.3 Crane spec barrel run fine without a moderator and without exhibiting the issues of the XM177. Not trying to be smart ass, but my upper isn't sprinkled with magic fairy dust. Physics haven't changed. What makes the difference? I usually run a can on it, but it runs without just fine. In fact I think .070 is a bit overgassed.
The MK18 developed for military use what makes it work, H2 or H3 buffer, proper sized gas port, vast majority of use with suppressor, vast majority of use with 70-77 grain heavy bullets. About the only time I can think of a military MK18 not being used with a suppressor or heavy bullets is if they are training with Simunition which doesn't work with suppressor's so they would run those fake Surefire SOCOM's.
So the question I have is why does my 10.3 Crane spec barrel run fine without a moderator and without exhibiting the issues of the XM177. Not trying to be smart ass, but my upper isn't sprinkled with magic fairy dust. Physics haven't changed. What makes the difference? I usually run a can on it, but it runs without just fine. In fact I think .070 is a bit overgassed.
A few things:
1) A new extractor spring.
2) A new magazine follower and spring.
3) A heavier buffer.
4) A new disconnect spring.
5) New feed geometry
And according to the reports, the 'moderator' was never intended to fix any reliability problems, it was in fact the source of several problems.
Oh, and by the way, most civilian ARs are under-gassed. Point one straight down and fire it, most will not lock back, nor (I suspect) will most work properly in arctic temperatures.
A few things:
1) A new extractor spring.
2) A new magazine follower and spring.
3) A heavier buffer.
4) A new disconnect spring.
5) New feed geometry
All of the above.
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