300 AAC blackout suppressor. Looking for basic build info

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icentropy
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300 AAC blackout suppressor. Looking for basic build info

Post by icentropy »

Hi all. first post. I'd like to start designing a 300AAC suppressor and wanted to see if anyone has the basic info such as internal volume, material and thickness of outer tube and baffles. I know most folks that Form 1 them up tend to severely overbuild to insure that they don't fail. I'm more interested in what the typical form 4 suppressors look like. I'd like something that is safe with supersonic 300 all the way down to .22LR so i'm assuming aluminum is out but i'd like to double check. I don't think i want to use titanium (harder to machine) so i suppose the other option is just stainless or steel. Here the thicknesses are even more important so i don't end up with a brick. I read that the 60° angle is the most widely used for K baffles. though i'm not sold on the K baffles as a mono-core might be much easier to machine. anyone have any idea of which would induce less shift in impact?

Thanks for any info.
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Re: 300 AAC blackout suppressor. Looking for basic build inf

Post by MCKNBRD »

OK, I'll bite.

Use the search feature here (admittedly, its a bit hard to sift through all the responses, but it is what it is) and scroll through the completed builds thread; Also, check out Dr. K's .30cal build. Look at the baffle pics thread, and Google search 'suppressor baffles'.

You get out what you put in; invest a little time reading the threads & searching for the info, then take your ideas & requirements and base your build concept applying current designs and ideas to your specific needs.

It ain't easy, but it is certainly rewarding.

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CMV
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Re: 300 AAC blackout suppressor. Looking for basic build inf

Post by CMV »

Simplest I can think of from a machining standpoint that would give good performance over the range of 300 BLK loads:

* 1.5" - 1.625" OD tube, .060"-.080" thick walls.
That would mean your bar stock needs to be the same diameter - at least enough for the endcaps. You would use 1.5" barstock for the baffles though with either (would need to be very nice piece for 1.625" OD & .060" wall tube though because you wouldn't be able to clean it up other than scotchbright w/o going undersize).

* Around 8"-10" OAL.

* Plain 60° cones with spacers. .050"-.060" thick.
Either machine the spacers into the cones (uses more barstock) or cut sections of smaller diameter tubing into rings to use to space the cones. You can clip the cones - ask others for input. I did not clip mine and am very happy with the performance. I think Kyle started with plain cones & then clipped them so he would be a good one to ask if it made any noticeable difference in sound or accuracy before/after. I think Shift1 (or someone else, but I think it was him) also recently did a similar style .308 with clipped cones. Number of cones is up to you. Blast chamber length, endcap style, mount type, & cone spacing will dictate number of cones/baffles.

* Bore size around a T drill at minimum, I used a U (.368").
Up to a 25/64" is probably just fine - depends on what you're comfortable with.

* Material is entirely up to you.
I used Gr9 Ti tube with 416 SS cones & 316L SS spacers. For machining simplicity I'd say 303 or 416 SS for the cones & end caps. The tube is going to be something crappy to work with - I don't know of any 'free machining' seamless tubing in those diameters. Doesn't mean it doesn't exist, just that I haven't seen it at the local metal supply yard or places like online metals. The threading tool I use - the 1/2" $40 here: http://www.mesatool.com/products/threading-tools/ - doesn't seem to mind Ti at all. But you could probably use 12L14 carbon steel for a no-weld design if you wanted - would just be more maintenance.

I won't give specifics for blast chamber or cone spacing I used because the person who helped me with it asked me not to share the spacing specifics. You can look at what others have done and some of the Xray or jalibroken commercial can pics and go from there to figure out something appropriate for your build.

Mine has threaded endcap & can be taken apart for cleaning. That's primarily due to my complete lack of knowledge/skill/ability to weld.
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Re: 300 AAC blackout suppressor. Looking for basic build inf

Post by Fulmen »

Sound's about right, I use a telescopic can 1.75" OF and 10,6" long.
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Re: 300 AAC blackout suppressor. Looking for basic build inf

Post by icentropy »

Thanks guys that's exactly what i needed. what thread size are you guys using for the end caps? It's looking like a 1 9/16 thread with 20TPI?
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Re: 300 AAC blackout suppressor. Looking for basic build inf

Post by Dr.K »

icentropy wrote:Thanks guys that's exactly what i needed. what thread size are you guys using for the end caps? It's looking like a 1 9/16 thread with 20TPI?
Single point thread on lathe, I use 28 pitch threads.
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Re: 300 AAC blackout suppressor. Looking for basic build inf

Post by CMV »

Dr.K wrote:
icentropy wrote:Thanks guys that's exactly what i needed. what thread size are you guys using for the end caps? It's looking like a 1 9/16 thread with 20TPI?
Single point thread on lathe, I use 28 pitch threads.
+1
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icentropy
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Re: 300 AAC blackout suppressor. Looking for basic build inf

Post by icentropy »

CMV wrote:
Dr.K wrote:
icentropy wrote:Thanks guys that's exactly what i needed. what thread size are you guys using for the end caps? It's looking like a 1 9/16 thread with 20TPI?
Single point thread on lathe, I use 28 pitch threads.
+1
But is the size of the thread 1.5625"? or just a custom size based on the ID of the tube? I'm trying to figure out how much material is safe to leave on the tube between the thread major diameter and the tube OD. I'm assuming that's the weakest point of the whole can.
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Re: 300 AAC blackout suppressor. Looking for basic build inf

Post by Dr.K »

icentropy wrote:
But is the size of the thread 1.5625"? or just a custom size based on the ID of the tube? I'm trying to figure out how much material is safe to leave on the tube between the thread major diameter and the tube OD. I'm assuming that's the weakest point of the whole can.
I don't know the mimumum safe thickness (it would be material specific), but I do know this as fact.

With a tube diameter of 1.5", grade 9 titanium, .070" wall thickness, 28 pitch threads cut into the ID, it will withstand hundreds of 308 blast without issue.

With that said, you definitely want to thread at least a half inch of the tube. I figure if you only had 1/4" of threads there, that's where weakness would show up.

And yes, my threads are custom. But, I take notes on everything so it is repeatable. Learning to cut threads is a whole subject that needs hours of study and practice to do competently. But, it is very rewarding also.
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Re: 300 AAC blackout suppressor. Looking for basic build inf

Post by icentropy »

Dr.K wrote:
icentropy wrote:
But is the size of the thread 1.5625"? or just a custom size based on the ID of the tube? I'm trying to figure out how much material is safe to leave on the tube between the thread major diameter and the tube OD. I'm assuming that's the weakest point of the whole can.
I don't know the mimumum safe thickness (it would be material specific), but I do know this as fact.

With a tube diameter of 1.5", grade 9 titanium, .070" wall thickness, 28 pitch threads cut into the ID, it will withstand hundreds of 308 blast without issue.

With that said, you definitely want to thread at least a half inch of the tube. I figure if you only had 1/4" of threads there, that's where weakness would show up.

And yes, my threads are custom. But, I take notes on everything so it is repeatable. Learning to cut threads is a whole subject that needs hours of study and practice to do competently. But, it is very rewarding also.
yes i have manual and CNC lathes and mills so the possibilities are endless but what I don't have is experience building suppressors or any on hand that i could take dimensions from.

So the hand guard i'll be using has a 1.75" ID which makes me think a 1.625 X .07 tube would be ideal. Do you guys think i'm leaving too little room? If i can get away with a 1.625" tube then taking a 28TPI thread and theoretically making it perfectly in a 1.485ID i'd end up with a 1.5237" nominal size thread.

i'm guessing blast chamber should be around 3" on a 8" can? Here's a design i quickly drew up. I'm thinking a Ti tube, CRES Caps and blast spacer and flat baffle and I'm wondering if i could get away with using aluminum on all the k-baffles or if that's a bad idea with supersonic .300BLK?

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Re: 300 AAC blackout suppressor. Looking for basic build inf

Post by Fulmen »

For a single silencer build there's nothing wrong with custom threads. Standards are there to ensure compatibility with other parts or mfgs, in this case performance is much more important. You can use single point threading, preferably full profile inserts, fine pitch and ID a hair over the tubes ID. Then single point the caps to fit.
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Re: 300 AAC blackout suppressor. Looking for basic build inf

Post by L1A1Rocker »

Be sure to do a bit of practicing on your threading. I recall my very first single point threading experience. I was so proud of these B-E-A-utiful, perfect 1/2 my 28 threads. . . until I realized they were left handed :shock:

But as you get more experience you'll be trying new and more advanced things. My next project is going to be two point ACME threads in titanium. Take things slow, read what others have done, practice a bit, and have fun. You really are on the correct path already. Good luck.
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Re: 300 AAC blackout suppressor. Looking for basic build inf

Post by Dr.K »

L1A1Rocker wrote:Be sure to do a bit of practicing on your threading. I recall my very first single point threading experience. I was so proud of these B-E-A-utiful, perfect 1/2 my 28 threads. . . until I realized they were left handed :shock:

But as you get more experience you'll be trying new and more advanced things. My next project is going to be two point ACME threads in titanium. Take things slow, read what others have done, practice a bit, and have fun. You really are on the correct path already. Good luck.
It became painfully obvious on my first set that the compound was set on 29.5°.........to the ways! :lol:
good thing it was on scrap.

The first barrel I chucked up, things were looking good then when I got to where I was cleaning up with a die I came to the realization that I had just cut a beautiful set of 1/2x 24 threads.........supposed to had been 28.

I've sure improved since those days. I've now been cutting threads for a year and a half pretty regularly, and things have gotten a lot easier.
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Re: 300 AAC blackout suppressor. Looking for basic build inf

Post by Dr.K »

icentropy wrote:
Dr.K wrote:
icentropy wrote:
But is the size of the thread 1.5625"? or just a custom size based on the ID of the tube? I'm trying to figure out how much material is safe to leave on the tube between the thread major diameter and the tube OD. I'm assuming that's the weakest point of the whole can.
I don't know the mimumum safe thickness (it would be material specific), but I do know this as fact.

With a tube diameter of 1.5", grade 9 titanium, .070" wall thickness, 28 pitch threads cut into the ID, it will withstand hundreds of 308 blast without issue.

With that said, you definitely want to thread at least a half inch of the tube. I figure if you only had 1/4" of threads there, that's where weakness would show up.

And yes, my threads are custom. But, I take notes on everything so it is repeatable. Learning to cut threads is a whole subject that needs hours of study and practice to do competently. But, it is very rewarding also.
yes i have manual and CNC lathes and mills so the possibilities are endless but what I don't have is experience building suppressors or any on hand that i could take dimensions from.

So the hand guard i'll be using has a 1.75" ID which makes me think a 1.625 X .07 tube would be ideal. Do you guys think i'm leaving too little room? If i can get away with a 1.625" tube then taking a 28TPI thread and theoretically making it perfectly in a 1.485ID i'd end up with a 1.5237" nominal size thread.

i'm guessing blast chamber should be around 3" on a 8" can? Here's a design i quickly drew up. I'm thinking a Ti tube, CRES Caps and blast spacer and flat baffle and I'm wondering if i could get away with using aluminum on all the k-baffles or if that's a bad idea with supersonic .300BLK?

Image
blast chamber is excessively large. I recommend taking it down to 1.6" in length. It has more to do with case+barrel volume than can length, and also type of propellant.
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Re: 300 AAC blackout suppressor. Looking for basic build inf

Post by icentropy »

Dr.K wrote: blast chamber is excessively large. I recommend taking it down to 1.6" in length. It has more to do with case+barrel volume than can length, and also type of propellant.
So assuming a 10.5" barrel shooting supersonic 300BLK a 1.6" chamber would be enough? I wasn't sure how it worked and how blast chamber vs number of baffles was calculated.
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Re: 300 AAC blackout suppressor. Looking for basic build inf

Post by Dr.K »

icentropy wrote:
Dr.K wrote: blast chamber is excessively large. I recommend taking it down to 1.6" in length. It has more to do with case+barrel volume than can length, and also type of propellant.
So assuming a 10.5" barrel shooting supersonic 300BLK a 1.6" chamber would be enough? I wasn't sure how it worked and how blast chamber vs number of baffles was calculated.
There is an old formula that H. Maxim came up with, I can't for the life of me reproduce it, but when I did the calculation based on my 9" blackout with 1.5 OD can, it worked out to 1.75"....So, with your 1.625" can...1.6" is a very reasonable number.

It'll have less FRP with subs also.
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Re: 300 AAC blackout suppressor. Looking for basic build inf

Post by icentropy »

Well I've modified the plans to move the blast chamber over to 1.6" from the end of the barrel. Also put a fillet on all the sharp corners to make machining and cleaning easier and increase the strength a bit on all the baffles and caps. On a separate but related note, I was looking into the tax stamp and have started thinking it might be better to simply get my 07 FFL and Class 2 MFG NFA license? From what i could see it's only $550 a year and that allows me to do R&D, and make them to my hearts delight. Seems like a pretty sweet deal even if i only do it for a few years.
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Re: 300 AAC blackout suppressor. Looking for basic build inf

Post by CMV »

Ask the 07/02's here about ITAR & see if it still sounds like a value vs $200 stamps. I don't know if they all MUST have it or only in certain circumstances, but it's a hefty fee.

You don't really need to do a lot of R&D - no need to reinvent the wheel. Get a good design with positive feedback here & then just make it. Making 60° cones & spacers to fit into a tube isn't overly complex & for 300 BLK will work well. Don't make it harder/more complex than it need be.

If you want to get your feet wet, do a rimfire can first. Smaller parts & more forgiving to less than perfect designs. But the same principles apply to larger builds - a tube with endcaps & baffles of some sort in between.
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Re: 300 AAC blackout suppressor. Looking for basic build inf

Post by icentropy »

CMV wrote:Ask the 07/02's here about ITAR & see if it still sounds like a value vs $200 stamps. I don't know if they all MUST have it or only in certain circumstances, but it's a hefty fee.

You don't really need to do a lot of R&D - no need to reinvent the wheel. Get a good design with positive feedback here & then just make it. Making 60° cones & spacers to fit into a tube isn't overly complex & for 300 BLK will work well. Don't make it harder/more complex than it need be.

If you want to get your feet wet, do a rimfire can first. Smaller parts & more forgiving to less than perfect designs. But the same principles apply to larger builds - a tube with endcaps & baffles of some sort in between.
From the little reading i did online it seems the ITAR $2K+ registration fee can be (and is usually) bypassed with a commodity jurisdiction request on pretty much any firearm/suppressor that you won't be exporting or is designed specifically for military applications. But I only just started looking into it so i might be way off base.

Here's the smaller blast chamber and an extra baffle. I'm starting to wonder if i'm over doing the wall thicknesses of the blast chamber. I'm allowing for a .100" wall all around and that's on top of the already .080" Ti tube. For the K baffles i'm thinking SS and .0625" thick.

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Re: 300 AAC blackout suppressor. Looking for basic build inf

Post by CMV »

Have you said what the baffle & blast chamber spacer are made from? .100 is kind of thick. .060 should be sufficient if it's stainless.

Here's another thought - what's the host? If it's an AR someone who knows better than I can tell you if K's or cones gives more backpressure. More back pressure = more s--t in your face. 300 BLK subs are dirty if you're loading with A1680.
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Re: 300 AAC blackout suppressor. Looking for basic build inf

Post by icentropy »

I do look longingly at the monocore designs though. Can anyone say that they're definitely quieter or definitely louder than the K or M baffle designs? It would be much easier for me to make a mono-core design as i'm more of a mill guy than a lathe guy (though i have both). Just by looking at the two options i would imagine the K/M baffles are probably a better design for accuracy and sound suppression but the monocore are cheaper to make and weight less. Here's a M baffle design i was messing with and the M4-2K i used to come up with the dimensions. I didn't stack them as closely together as the M4-2K though as it just looks way too close together for some reason. Here i removed the blast baffle and reduced the blast sleeve to .0625". I'm leaning towards making all internal components out of 304L CRES and the tube out of 3Al-2.5V Ti. The Ti would save me about 6 oz on the tube alone.

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Re: 300 AAC blackout suppressor. Looking for basic build inf

Post by icentropy »

CMV wrote:Have you said what the baffle & blast chamber spacer are made from? .100 is kind of thick. .060 should be sufficient if it's stainless.

Here's another thought - what's the host? If it's an AR someone who knows better than I can tell you if K's or cones gives more backpressure. More back pressure = more s--t in your face. 300 BLK subs are dirty if you're loading with A1680.
Yes it'll be on a 10.5" AR
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Re: 300 AAC blackout suppressor. Looking for basic build inf

Post by MCKNBRD »

As a general rule, monocores are louder. (I know, I know...I'm going to get flamed like crazy for that...but its true. Especially regarding FRP) They also tend to be heavier.

60* clipped cones are popular for a reason. The last diagram you posted shows an 'M' style baffle...thinking purely in work operations and setup, why would you go that route vs. a spacer on the back of the cone? The M baffle requires a 2nd operation, which can lead to concentricity issues. K-baffles will give you a more pronounced backpressure curve, like CMV alluded to. Of course, if you're shooting 5.56 through a .30 cal can, it will help offset it a BUNCH.

After my experience a couple of weeks ago, where I got to listen to many different cans on many different hosts, I'm not completely sold that you need tons of baffles. More baffles might meter better, but to my ear, I couldn't tell a whole lot of difference between an M4-1k, a Lane Scorpion, a 762-SDN-6, or an M4-2k. Centerfire supersonic is just LOUD. The suppressor helps mitigate a LOT of the noise, but I was really surprised at the overall sound. Its gotten me going back to the drawing board, for sure.

If you're going to be suppressing an SBR AR, its probably not a bad idea to thicken up the blast baffle as much as you can. Might even consider the added complexity of using a muzzle brake as a sacrificial blast baffle.

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Re: 300 AAC blackout suppressor. Looking for basic build inf

Post by icentropy »

MCKNBRD wrote:As a general rule, monocores are louder. (I know, I know...I'm going to get flamed like crazy for that...but its true. Especially regarding FRP) They also tend to be heavier.

60* clipped cones are popular for a reason. The last diagram you posted shows an 'M' style baffle...thinking purely in work operations and setup, why would you go that route vs. a spacer on the back of the cone? The M baffle requires a 2nd operation, which can lead to concentricity issues. K-baffles will give you a more pronounced backpressure curve, like CMV alluded to. Of course, if you're shooting 5.56 through a .30 cal can, it will help offset it a BUNCH.

After my experience a couple of weeks ago, where I got to listen to many different cans on many different hosts, I'm not completely sold that you need tons of baffles. More baffles might meter better, but to my ear, I couldn't tell a whole lot of difference between an M4-1k, a Lane Scorpion, a 762-SDN-6, or an M4-2k. Centerfire supersonic is just LOUD. The suppressor helps mitigate a LOT of the noise, but I was really surprised at the overall sound. Its gotten me going back to the drawing board, for sure.

If you're going to be suppressing an SBR AR, its probably not a bad idea to thicken up the blast baffle as much as you can. Might even consider the added complexity of using a muzzle brake as a sacrificial blast baffle.

Byrdman
I went with the M baffles vs spacers just to decrease the amount of parts. concentricity shouldn't be too much of an issue as keeping them within .001" to each other won't present much of a problem.

Thanks for the monocore info. I expected that to be the case but i wasn't sure and it's good to hear it from someone else. I'll continue with my baffle plan. If K baffles present more backpressure (and i can see how that would be the case) then M baffles it is.

I'm not sure what you mean by using a muzzle brake as a blast baffle? I thought the blast baffle was mostly to keep the wear off of the rest of the baffle stack?
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Re: 300 AAC blackout suppressor. Looking for basic build inf

Post by gunny50 »

MCKNBRD wrote:As a general rule, monocores are louder. (I know, I know...I'm going to get flamed like crazy for that...but its true. Especially regarding FRP) They also tend to be heavier.

60* clipped cones are popular for a reason. The last diagram you posted shows an 'M' style baffle...thinking purely in work operations and setup, why would you go that route vs. a spacer on the back of the cone? The M baffle requires a 2nd operation, which can lead to concentricity issues. K-baffles will give you a more pronounced backpressure curve, like CMV alluded to. Of course, if you're shooting 5.56 through a .30 cal can, it will help offset it a BUNCH.

After my experience a couple of weeks ago, where I got to listen to many different cans on many different hosts, I'm not completely sold that you need tons of baffles. More baffles might meter better, but to my ear, I couldn't tell a whole lot of difference between an M4-1k, a Lane Scorpion, a 762-SDN-6, or an M4-2k. Centerfire supersonic is just LOUD. The suppressor helps mitigate a LOT of the noise, but I was really surprised at the overall sound. Its gotten me going back to the drawing board, for sure.

If you're going to be suppressing an SBR AR, its probably not a bad idea to thicken up the blast baffle as much as you can. Might even consider the added complexity of using a muzzle brake as a sacrificial blast baffle.

Byrdman

;-)
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