That is a very valuable contribution to the discussion, Sigfreund; thank you. I am going to alter the thread title, to broaden the paramaters of the conversation. A great example of how almost everything is a give-and-take, when it comes to "weapons theory".

Similiar effect of a vapor trail behind a high flying jet.
Heated exhaust meeting the cooler air at altitude creating vapor trail.

Indeed. The silencer exacerbating the phenomenon is due to the gasses moving slower, perhaps?

Tested the patience and insect tolerance threshold of my camera operator (wife) last night, and conducted a somewhat scientific test.

Two weapons; one serving as a "control", and the other as "optimized":
Colt 933
11.5" barrel
M855
SF RC2 (no ablative)
ATPIAL laser (active)

"Recce carbine"
14.5" barrel
Hornady 75gr HD-SBR
Otter Creek OCM5 (ablative)
Eotech EXPS3-0 (passive)

I viewed three shots through each weapon with and without a Gen3 white phos PVS14, from a distance of about 50m, slightly forward of the muzzle.

Without night vision, the only visible signature was the flash on the first round fired from the Colt.

Through night vision, the shortcomings of the control setup were visible:
-a minor muzzle flash on all rounds fired
-a bright dot at the laser aperture
-the temporarily visible laser beam, in the post-shot muzzle vapor

And the performance of the optimized:
-tiny muzzle flash on first round only
-no laser effects
-vapor cloud larger, and visible. It did not compromise visibility of the target, but would be a signature concern, especially in the test conditions (open pasture). I think the cloud would be much less of a give-away in the woods or an urban setting, where there is more concealment.

Another note, on the control setup, is the favorable atmosphere, on the night of the test. The air was clear, with no lingering haze. In the past month or so, of the times I used an IR laser, the beam was more often than not a lightsaber, due to suspended moisture in the air. This is not representative of all laser usage cases, but certainly represents more circumstances than laser advocates would have you believe. That's a bad visible signature: one that shows where you are before you fire, shows what you're attempting to engage, and draws a line between the two.

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Turns out the ablative is not worth messing with unless maximum nighttime signature reduction is critical. I did a little shooting today, and it takes quite a while for the vapor effect to wear off. I fired between ten and fifteen rounds, confirming zero at a few different distances, and the leftover ablative from the other night's test gave me a not-insignificant cloud on every shot. So, to add ablative for a potential nighttime use of the rifle, only to have the event not occur, would have you left with a silencer that will give you a very bad signature enhancement during daylight hours. Using an ablative other than oil may mitigate the issue; something like water would burn off quicker, but then you're potentially introducing water to the interior of your silencer for an extended period, which isn't ideal.

To return to this thread, these are images from a video about a preferred sniper rifle used by both sides in Ukraine. It’s a locally-manufactured AR-10 type model, and these photos show the visible cloud of gas from the bolt carrier when the weapon is fired in cold temperatures. Like the signature from suppressors in similar conditions, it dissipates very quickly, but it’s nevertheless there.





In this second picture, part of the cloud is from the suppressor, but most of what’s visible is evidently from the bolt carrier through the ejection port.





Video

Another demonstration of using a suppressor in weather cool enough for the shooter to be wearing a coat.

I appreciate the continued contributions, sigfreund.

Recent discussion in hrcjon's SF RC3 thread, and associated video evidence, illustrates that muzzle device choice can have a significant impact on silencer flash performance. This likely varies across different manufacturers' device and silencer designs.

And also sound performance. Want an example just hit up pew science on the Surefire RC2. There is a huge difference in sound suppression when using the warcomp!

This KAC can is pretty slick. Too bad it'll run you $1.800! The other videos in this "series" are all done in the same format, making for a great comparative setting.

This video goes well with the Rooftop Defense video series. The visible signature of the silencer itself is no small thing, especially in the IR spectrum. Mr. Brass Facts equates the IR signature of a hot can to a civilian-legal IR illuminator (not being pointed directly at the viewer). That's a pretty big deal, considering you can't turn the hot silencer off, to cease the signature.

quote:

Originally posted by KSGM:
The visible signature of the silencer itself is no small thing ....

An interesting video. I had trouble following some of the discussion, probably because I’m not familiar with much of the terminology and practices being mentioned, but the technical detail was impressive.

Because of my ignorance due to having only one suppressor and that’s just used for very low volume precision rifle fire, now I have a specific question about the visibility of a hot can by itself: why aren’t suppressor covers used?

As I say, I have no experience with the type of shooting covered in the video or the suppressors themselves, but is there some reason for not using covers other than the extra bulk and weight they add? Magpul has a cover that’s rated for “extreme” heat, but is that not true of other common offerings?

I would think it would be very dangerous to “operate” with an uncovered can that was anywhere close to being hot enough to be seen glowing even with NV. My TBAC suppressor gets too hot to touch after firing five quick rounds of 308 Winchester, so I can’t imagine handling some of the ones pictured in the video. What say ye?

Of course I can't scan myself shooting, but for sure covers help at least from the obvious tactile heat level. But I don't think anything is going to mask the heat signature completely under high volume fire. (and if you watched that Surefire rc3 test that can is unbelievably hot). But realistically the rest of the gun is also equally hot at least with respect to seeing it on thermal. You can't touch the barrel on my 249 after a mag and I'm sure one could see the gun from a very long distance under thermal. Even slow fire from my bolt gun has the suppressor hot enough that I think its probably quite visible. Since thermal has its own set of signature issues to manage I'm not sure what the best protocol's are. I've not seen it discussed very widely. Me, in my terrain, it would be pretty easy to get the gun behind something after shooting. But it takes an inordinate amount of time for cooling to happen. Maybe you use a 249 and when your done grab the barrel and suppressor and toss them in water and install the next one. anyway interesting angle. I'm liking thermal better all the time FWIW...

quote:

why aren’t suppressor covers used?

I am not sure why covers aren't more popular in the, what we'll call, "tactical carbine" world. I have never really used one, or really felt the need for one. I have a Manta rubber cover that I got from a friend, years ago, but The weight and bulk of it have never seemed worth the benefits.

The Manta covers are supposed to be quite good. The Magpul cover you referenced seems to have potential drawbacks, due to weight/bulk and hardware, based on reviews I looked up. The textile "wrap" covers seem to have problems staying attached, and aren't seemingly up to the task of higher temps, based on feedback I've read online.

It seems, if this visible heat-related signature (or lack thereof) is important to a user, he'd do well to seek a can that is itself inherently slow to heat up.

I may try to employ that Manta of mine again. As I recall, it's easy-on; not so easy-off. So, I'm hesitant.

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The bit about tubeless cans made me wince a bit. Both the cans I have in jail are tubeless. The selling point he mentions with the reduced weight is true, but I also see faster cooling mentioned as a selling point that he didn't touch on. Of course, if you have to heat your can up enough that it's emitting enough IR to be a problem, waiting for it to cool down might not be a luxury you have. Suppressor covers might mitigate the signature enough to not be noticeable at certain distances, but you're also holding that heat in the can. Build up enough heat, and stuff starts warping and melting.

All I could think of watching that video is that this is just another way that both suppressors and night vision are worlds where absolutely everything is a tradeoff and no perfect solution yet exists.

There is obviously a point at which every can has heat limits. But heat gain and loss is ultimately mostly about mass and not so much about construction. That said any can that survives the socom surge testing cycle is never ever going to be hot enough in civilian use to worry about warping and melting. I have access to very sensitive IR and temp measuring equipment which I have occasionally used on guns. Most recently I did that when I got my Ti thunderbeast as they actually specify a max temp for it. So I fired it and monitored it. The max is seriously not an issue for my use. When I get some spare time I'll drag the gear to the range and look at the issue in question which is IR signature under various firing schedules.

quote:

Originally posted by hrcjon:
... grab the barrel and suppressor and toss them in water and install the next one.

This reminded me of something I read in a memoir of a German army soldier who was a machine gunner in WWII. He said they were cautioned to not force cool hot barrels after they were removed for a switch in sustained firing because that would cause them to warp. That was in reference to dropping them in the snow, but based on a couple of unwise (as it turned out) incidents with saucepans that had been allowed to boil dry, I had learned that myself: Letting them cool down normally was fine; putting them in cold water caused the bottoms to buckle.

I have ruined a frying pan that way too. I think some more modern firearms parts are more resistant to that phenomenon than the German machine gun barrels you mentioned. I have read an article about, coincidentally, a German (HK) machine gun (HK21E) whose barrel could be fired to scorching conditions, quenched in water, reinstalled, and then produce a MOA group in single fire.

This message has been edited. Last edited by: KSGM,

quote:

Originally posted by KSGM:
I have read an article about, coincidentally, a German (HK) machine gun (HK21) whose barrel could be fired to scorching conditions, quenched in water, reinstalled, and then produce a MOA group in single fire.

Thank you. Anything related to technology has obviously been subject to improvement in the past 80+ years, and it would be interesting to understand the bases for the difference*. I assume it has to do with alloys and/or heat/cold(?) treatments. And what other quick barrel switch automatic weapons would all that affect?

Sorry for the thread drift, but these are the sorts of things that I find interesting to discuss on a firearms-related forum.

* And why did HK decide to make that possible? Was there institutional knowledge and perhaps concerns dating back to the war?