"Baffle" material?

Yes, it can be legal to make a silencer. For everything Form-1, from silencer designs that are easily made, to filing forms with the BATF, to 3D modeling. Remember, you must have an approved BATF Form-1 to make a silencer. All NFA laws apply.

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DLrocket89
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"Baffle" material?

Post by DLrocket89 » Wed Nov 30, 2016 1:03 pm

Hi everyone,

I'm hoping to be able to start a Form 1 in the next year or so...wiping out the last of student loans and whatnot and then will get started.

I have half a dozen different firearms I'd like to build silencers for, and they run a wide range. 22 rifle, 17HMR rifle, 22 pistol, 308 rifle, 762x39 rifle, etc. I've spent some time looking over designs of others here, so I have a basic understanding of how things go ("very basic").

When looking at McMaster Carr today to get a feel for prices, I came across the following material:

https://www.mcmaster.com/#aluminum-foam/=159lozq

Rigid aluminum foam. I don't expect it to hold up to a 308 or anything, but what about for a 22LR? Make one "blast baffle" to handle the brunt of the heat and then 6" or so of that material with a hole through it.

...Lets say for a moment that I have access to a laser cutter, so cutting circles out would be cake.

Thanks!

Dustin
Wisconsin, USA

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Capt. Link.
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Re: "Baffle" material?

Post by Capt. Link. » Wed Nov 30, 2016 1:18 pm

I would build a .22 rimfire suppressor first.Use stainless steel and K baffles.Porous metals have been used in the past but are not economical to construct under current NFA law.
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DLrocket89
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Re: "Baffle" material?

Post by DLrocket89 » Wed Nov 30, 2016 2:18 pm

Hi Capt. Link,

Thanks for the reply. I'm guessing that by "not economical" you mean that because I'd be making and not manufacturing, I can't make replacement baffles for it and the foam aluminum will wear out whereas stainless K baffles won't?

Thanks again!

Dustin

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Re: "Baffle" material?

Post by Capt. Link. » Wed Nov 30, 2016 3:14 pm

DLrocket89 wrote:Hi Capt. Link,

Thanks for the reply. I'm guessing that by "not economical" you mean that because I'd be making and not manufacturing, I can't make replacement baffles for it and the foam aluminum will wear out whereas stainless K baffles won't?

Thanks again!

Dustin
Even with advanced baffle design the returns would be much less than conventional designs plus a shorter lifespan.Its not time and money well spent even if you had the license and could experiment.R&D is very expensive I've tossed many buckets of baffles in my day.
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Re: "Baffle" material?

Post by a_canadian » Wed Nov 30, 2016 3:21 pm

A356 being a casting alloy doesn't seem a very strong choice, even for .22lr. But even more obviously I should think is that the bubbles seem to be randomly sized and located, with little if any inter-chamber ducting between them. As such your use of such bubble chambers as 'baffles' in a monolithic suppressor core would be severely limiting, owing to most of these chambers being in isolation. Actual trapped volume of expanding combustion gases would be minimal as suppressors go, resulting in very little reduction in volume. If your intention was to make smaller individual baffle blocks (like thick bubbly washers with tubular spacers separating them) from the stuff suppression might improve, owing to cutting through more bubbles, but then strength would be severely compromised. Aluminum foam may be useful as an acoustical tile material, but I really doubt it'd prove useful for suppressors.

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Re: "Baffle" material?

Post by DLrocket89 » Wed Nov 30, 2016 8:09 pm

Thanks for the replies everyone, this makes sense.

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Re: "Baffle" material?

Post by yondering » Wed Nov 30, 2016 10:27 pm

I disagree, I think it's actually a pretty reasonable idea.
A356 can be plenty strong enough for a 22 LR suppressor, especially in a material like that where it's mostly surface skin; it depends on the structure and baffle shape though. I think that stuff is worth a shot; personally I'd choose the large cell version of course. I'd be surprised if it held up to centerfire rifle full power loads, but subsonic 30 cal and 9mm might be OK.

I don't buy in to the thinking that suppressors have to be way overbuilt and you need to use stainless and Ti for .22 cans. Make it overkill if you want, but all you're gaining is weight and resistance to ham-fisted cleaning.

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Re: "Baffle" material?

Post by Bah21963 » Wed Nov 30, 2016 10:40 pm

Except the ATF prohibits replacing baffles unless done by 07/02 SOT. Then the cost goes way up. That's the reason to build the most durable efficient suppressor the first time. I prefer to build multical cans that preform and last.

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Re: "Baffle" material?

Post by yondering » Wed Nov 30, 2016 11:39 pm

Bah21963 wrote:Except the ATF prohibits replacing baffles unless done by 07/02 SOT. Then the cost goes way up. That's the reason to build the most durable efficient suppressor the first time. I prefer to build multical cans that preform and last.
"Except" what?

Have you actually worn out a .22 rimfire suppressor, or even seen one worn out other than by abusive cleaning? You can build or buy a very light aluminum 22 can that will last as long as your guns, and way beyond the point where you'll want to buy or build something better down the road anyway.

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Re: "Baffle" material?

Post by a_canadian » Thu Dec 01, 2016 12:23 am

I've seen substantial pitting in the first K baffle when using 6061 with .22lr and no ablative medium. Strictly subs. After maybe 300 shots fired. Started using lithium grease at that point and switched to 7075. Cleaning has been strictly toothbrush, solvents (alcohol, acetone) and cotton cloth. At the rate it was going the 6061 baffle might have lasted a few thousand rounds before collapsing when it looked something like Swiss cheese.

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Re: "Baffle" material?

Post by Bah21963 » Thu Dec 01, 2016 2:19 am

yondering wrote:
Bah21963 wrote:Except the ATF prohibits replacing baffles unless done by 07/02 SOT. Then the cost goes way up. That's the reason to build the most durable efficient suppressor the first time. I prefer to build multical cans that preform and last.
"Except" what?

Have you actually worn out a .22 rimfire suppressor, or even seen one worn out other than by abusive cleaning? You can build or buy a very light aluminum 22 can that will last as long as your guns, and way beyond the point where you'll want to buy or build something better down the road anyway.
A365 would either clog or wear quickly, less than 1000 rounds I would estimate. A form 1 maker could not replace the A365 without breaking the law. Personally I wouldn't want to lose the ability to own firearms by committing a felony as stupid as replacing a firearm part not allowed. I also use my 22 cans on 22 mag and 17 hmr. I find it a lot easier to shoot about 20 rounds of 556 to clean the cans instead of scrubbing or other cleaning methods. My grandkids will have as much fun with my cans as I do.

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Re: "Baffle" material?

Post by DLrocket89 » Thu Dec 01, 2016 3:47 pm

I was kicking this one around with my boss today (PE mechanical engineer who loves firearms) and came up with another idea.

Basically, make a knockoff of the Silencerco Osprey, and just put a block of the large open cell material in the square bottom of the can body. Add water to taste, maybe even some silicone on the bottom of the aluminum foam to absorb shock and whatnot.

Large volume in the can but with it hanging lower you don't "see" it, it's all aluminum so the weight isn't bad, crazy high surface area to absorb heat and slow gas down, no direct exposure to gases for the A356... Gotta think that at least has a shot of being a decent idea?

Sidenote, I'm a metallurgist and used to work in aerospace. We made a TON of aircraft generator housings out of A356...good stuff. More resilient than the words "cast" and "aluminum" would initially imply.

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Re: "Baffle" material?

Post by BinaryAndy » Thu Dec 01, 2016 6:56 pm

Hey, this is actually a pretty neat idea, and I have a feeling it might *almost* work. I don't think I've ever seen the stuff in person, but the large-cell version reminds me of a hyper-complex and randomized, but not terrible, monocore design. Sure, there might be some cells that are mostly or entirely closed off which would cost you some volume, but 22 cans don't need much volume anyway so I wouldn't worry about that.

Again, I've never handled aluminum foam so I'm just guessing about its strength, but I'd be a bit surprised if the actual strength of the material turned out to be an issue here. I've done some experimentation with pretty aggressive weight-saving schemes, and I'm discovering that it's really pretty difficult to make a suppressor that does not hold up to the blast from 22LR, without also making it impractically fragile. I made a stack of very light K baffles a little while back that had zero problems holding up to 500 rounds of HV 22lr from a pistol and probably could have lasted for thousands and thousands, but it was way too easy to permanently compress the baffles by accident while tightening the end cap. Erosion is a different matter of course, and I have no way to guess how long aluminum foam would last before too much of it would wear away.

The biggest problem with the aluminum foam idea is cleaning. Nice smooth baffles in a 22 can are already enough of a pain to clean, especially when they're made of aluminum. I don't see any way you could ever clean all of the crud out of a metal foam without using chemicals like the dip, which you can't use on aluminum anyway. Maybe a very powerful ultrasonic cleaner with milder chemicals would do it. You would never be able to clean it manually.

If you can find a way around the cleaning problem, then you might be on to something.
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Re: "Baffle" material?

Post by DLrocket89 » Thu Dec 01, 2016 8:49 pm

Yeah, that makes sense. Ultrasonic jewelry cleaners are $25 on amazon, so that's not a big deal. I might see if I can find a silicone "release" spray, like basically mold release. From working with silicone before, the short version is "silicone sticks to anything, but nothing (except silicone) sticks to silicone". Find a silicone spray and spray/soak the foam in that, let it dry to a thin film. I'm sure it won't be 100%, but it'll take the heat and if it's only 95% effective that's pretty darn good!

My boss has worked with the aluminum foam stuff before, he said that the large cell material is completely open - the cells all connect to each other. if it is a problem, it would be cake to take a 1/4" drill and drill some holes in it to make sure everything is "interconnected".

Sadly it'll be awhile before I get to try this out (figure a year at least), but it'll be at the top of my list.

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Re: "Baffle" material?

Post by yondering » Thu Dec 01, 2016 9:33 pm

DLrocket89 wrote:Yeah, that makes sense. Ultrasonic jewelry cleaners are $25 on amazon, so that's not a big deal. I might see if I can find a silicone "release" spray, like basically mold release. From working with silicone before, the short version is "silicone sticks to anything, but nothing (except silicone) sticks to silicone". Find a silicone spray and spray/soak the foam in that, let it dry to a thin film. I'm sure it won't be 100%, but it'll take the heat and if it's only 95% effective that's pretty darn good!

My boss has worked with the aluminum foam stuff before, he said that the large cell material is completely open - the cells all connect to each other. if it is a problem, it would be cake to take a 1/4" drill and drill some holes in it to make sure everything is "interconnected".

Sadly it'll be awhile before I get to try this out (figure a year at least), but it'll be at the top of my list.
There have been some threads here about using silicone (DOT 5 IIRC?) brake fluid for treating baffles this way, to make cleaning easier.

If you have access to one, a bead blaster at low pressure (not abrasive, but glass beads) works really well for cleaning 22 baffles without damage. I run mine at about 35 psi for baffle cleaning, and can still see the machine marks after many thousand rounds. I don't know how well it would work on that foam, but if the cells are pretty open, and the baffles aren't real thick, it might work fine.

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Re: "Baffle" material?

Post by BinaryAndy » Thu Dec 01, 2016 10:35 pm

DLrocket89 wrote:Ultrasonic jewelry cleaners are $25 on amazon, so that's not a big deal.
A jewelry cleaner isn't going to touch rimfire crud. I had an ultrasonic reloading brass cleaner that was a good deal larger and more powerful than a jewelry cleaner, but I stopped using it because it was taking too long to clean rifle and pistol brass. The stuff that collects in a 22 can is far more stubborn than the residue in centerfire brass. I was thinking of something heavy-duty and impractical.
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Re: "Baffle" material?

Post by yondering » Fri Dec 02, 2016 2:26 am

BinaryAndy wrote:
DLrocket89 wrote:Ultrasonic jewelry cleaners are $25 on amazon, so that's not a big deal.
A jewelry cleaner isn't going to touch rimfire crud. I had an ultrasonic reloading brass cleaner that was a good deal larger and more powerful than a jewelry cleaner, but I stopped using it because it was taking too long to clean rifle and pistol brass. The stuff that collects in a 22 can is far more stubborn than the residue in centerfire brass. I was thinking of something heavy-duty and impractical.
Same experience here (and why I mentioned the bead blaster above). I even went so far as to chip off bits of rimfire fouling from my baffles and experiment with them in all the solvents and cleaning solutions I had, in the ultrasonic cleaner, nothing dissolved or broke them up that was also safe for aluminum.

As for brass cleaning (warning- thread drift), I gave up on the US for that too. My US cleaner holds 2 quarts, meaning it could handle a few handfuls of brass, maximum; it generally took about 30 minutes to get those clean. Instead, I switched to a solution of lemon juice, white vinegar, and dish soap mixed with hot water in a bucket, and clean several thousand pieces of brass at once, just letting it soak for a bit. Then I dry it in the oven @ 200*F, and toss them in the tumbler with corn cob; they come out looking better than new brass.

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Re: "Baffle" material?

Post by mcmaster » Fri Dec 02, 2016 3:49 am

If you drilled small holes through the foam the chambers would connect together for sure.

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Re: "Baffle" material?

Post by alordnapa » Fri Dec 02, 2016 10:37 pm

It would be interesting to see how spongiform the material is. If it is very porous, a baffle made from this material would be much like the "Donuts" Mitch Werbel of Sionics used to make. In fact, suppressors made with nothing but a cast copper cores, loaded with rock-salt, and dissolved out with water after casting to make it spongiform, are very effective, especially as wet suppressors. They don't even really need an outer tube! Copper and Aluminum of course have very different specific heat constants, but water would make a great equalizer. The bore has to be cast into the donut; if you try to drill through it, the pores will smush together and close up. This approach has the very nice advantage of using the soft core to absorb much of the mechanical noise that is otherwise present in hollow tube designs, which "ring" noise all across the audio ( And beyond) spectrum. The Sionics suppressors used these donut baffles for submachine guns, but I believe they were considered consumables ( Mitch Werbel was way before my time) Which would of course be a problem for a non-SOT.

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Re: "Baffle" material?

Post by whiterussian1974 » Mon Jan 16, 2017 7:43 am

Instead of a Baffle, I'd like to have a 7/02 make one as an endcap for me. It would work as a diffusor does on Hairdryers, and jet exhaust from Helicopter Turbo-shafts.
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