What's the history behind the moderator?

[MSW]

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.

[mark5pt56]

[/B]

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.

[mack7.62]

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".

[MSW]

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.

[ABNAK]

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.

[okie]

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?

[lysander]

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.

[utahjeepr]

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.

[ABNAK]

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!

[mack7.62]

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.