DISCLAIMER:
I’m assuming that if you are reading this, you are an intelligent adult who is aware of what laws govern sound suppressors in your country. In my country (the good ol’ U.S. of A), it is illegal to manufacture a suppressor without seeking approval and obtaining a tax stamp from the Bureau of Alcohol, Tobacco, Firearms, and Explosives (BATFE) via a Form 1, or via obtaining a Class 2 Federal Firearms License and paying the appropriate Special Occupational Tax (SOT). Don’t be stupid. Follow all laws and play by the rules.
If you haven’t already guessed from my post about making a .300 Blackout piston gun, I’ve been super fascinated by sound suppressors over the past two years. It’s hard to believe, but almost one year ago I built my very first sound suppressor out of a Maglite flashlight (via ATF Form 1). Since then, I’ve procured a SilencerCo Harvester 30 and made another Form 1 suppressor. One of the things that truly astounds me about suppressors is the technology and engineering involved in making them work effectively. Now that I’m fresh off of my second suppressor build, I thought it would be a great time to go over some ideas I’ve had about sound suppressor design.
One of the tasks you must accomplish prior to filing an ATF Form 1 is to draw up a diagram that you will submit with the form. I truly enjoyed this part of the process because it pushed me to look around and get inspired by all of the different designs out there used by the big name manufacturers. One bit of inspiration came when I stumbled across a post by the Truth About Guns blog that has photographs of several big name manufacturer’s suppressors cut in half, exposing their baffle designs. Check it out.
It sounds weird, but I could look at suppressor cutaways just about all day and it would just pump me up about wanting to design a baffle stack…
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Oh, sorry… got lost in them again…
Since I’ve been staring at those photographs for far longer than I will ever admit, I’ve begun to postulate about what design features might make suppressors quiet and efficient. Before we delve into this, however, let’s go over and define some nomenclature:
Suppressor Body/Main Tube – this is the exterior portion or tube portion of the suppressor.
Suppressor Baffles – These are the structures within the suppressor that disrupt the flow of propellant gases as they exit the barrel and form chambers within the suppressor which allow those gases to expand to a lower pressure. They come in all different shapes, but we will be using conical ‘M’ baffles in this discussion.
Primary Blast Baffle/Chamber – This is the very first baffle in the baffle stack. It creates a chamber that will take the major brunt and abusive force of the propellant gases right as they enter the suppressor. I like to reinforce the primary blast chamber using thin steel tubing (it will also act as a spacer for adjusting volume).
Thread Attachment – I wasn’t sure what to call this one, but this is the back end of the suppressor that affixes to the barrel. This can either be directly threaded to the barrel, or somehow affixed to a threaded muzzle device.
End Cap – This is the front end of the suppressor that holds the suppressor together and is the last thing the bullet will travel through.
General Design
There is a lot of hearsay on the internet about proper suppressor design in conjunction with intended use. What does that mean exactly? Well, the word on the web is that for high pressure, high velocity rounds, you need more volume and fewer baffles. For lower pressure, low velocity rounds, you need less volume and more baffles. Why? Because reasons (obviously). Let’s look at one more image I shamelessly stole from the internet that seems to demonstrate the cartridge max pressure to suppressor volume hypothesis.
As you can see, all of the centerfire rifle suppressors have large internal volumes and fewer baffles…. Hmmmmmmmm…
If there is any single truth I do know about suppressor physics, it is this: It’s effing complicated. If you took a look at the suppressor cutaways, you probably saw that there are many different designs out there and some of them seem to demonstrate the web’s pressure/volume theory. However, what I can conclude from my ‘research’ is that there doesn’t seem to be a consensus in the suppressor industry as to what design elements make one sound suppressor quieter than others. Be that as it may, there does seem to be one universal principle: For a suppressor to be effective, it needs baffles to disrupt and slow down the flow of gases exiting the barrel, and it needs internal volume for those gases to expand and pressure to dissipate. There doesn’t seem to be much compromise in this regard; you need both to be quiet. We’ll call this the baffle/volume principle.
Let’s take a look two examples from SilencerCo (I do not own the picture below; I selfishly stole it from a Pintrest post).
The image above is a cutaway look at a Specwar 762 (top) and a Saker 762 (bottom) from SilencerCo. Both of these sound suppressors are rated all the way up to .300 Remington Ultra Magnum (roughly 65,000 PSI max pressure). As you can see in both suppressors, there is a larger volume of space between the muzzle and the primary blast baffle than between all of the following baffles in the baffle stack. That is because the majority of expansion from the propellant gases will take place just as they leave the muzzle. Now, it is good to note that the Specwar has much more volume for expansion and one more baffle than the Saker. According to SilencerCo’s website, the Specwar is also quieter…
Now, SilencerCo is able to make a short .300 RUM suppressor like the Saker 762 with such little volume by using incredibly strong, and equally as expensive Stellite for baffling that is fully welded to a stainless steel inner tube, making a solid brick-shithouse. The average consumer won’t have the machinery or money to build such a tenacious critter like the Saker 762, so if the common man (or woman; I don’t stereotype) decides to build a suppressor, they need to have proper internal volume to make a safe and effective suppressor. Just remember this principle: The higher the pressure, the more volume is needed for those gases to safely expand and slow down. If you don’t accommodate the needed expansion volume properly, you might make an unsafe suppressor or at least one that’s not as quiet as it could be.
I digress…
In regards to the baffle/volume principle, the most effective sound suppressor ever made would technically have a considerable amount of volume and an ungodly number of baffles. Unfortunately, unless you want to carry around a retrofitted water heater filled with massive funnels to suppress your gun, you must find a compromise that will fit the suppressor’s size and intended use. Because of this compromise, there will be a battle for the suppressor’s internal volume as it is consumed by baffle material. For each baffle you put into the suppressor, that is volume being displaced by baffle material. So, a general rule of thumb to consider is: More baffles = less volume | Less baffles = more volume.
Let’s say we want to build a suppressor that is 8″ long in overall length, with a main tube interior diameter of 1.35″. In this scenario, the end caps will take up roughly .25″ on either end of the suppressor, giving us a main tube of about 7.5″ in length. The end caps will also thread into the main tube about 0.5″ on both ends, giving you roughly 6.5″ of space inside of the main tube.
Ideally, we want to use as many baffles as possible whilst retaining as much of the original volume as possible. Now, for you math geeks out there, 1.35″ inner diameter with 6.5″ of length = 9.3 in³ of volume. If you were able to find baffle material, like a 1.35″ diameter, 0.5″ tall steel cup with 0.125″ thick (1/8″) walls, or about the rough dimensions of an appropriate freeze plug, it would take up about 0.42 in³ per baffle. Let’s go further by saying that the spacer tube you plan to use is roughly 1.35″ outer diameter with 0.125″ thick walls, you can subtract 0.32 in³ for every 0.5″ of spacer tube used.
Let’s start with a high-pressure cartridge setup as a benchmark (for supersonic .308 Winchester or 5.56 NATO). We will have a 2″ primary blast chamber, 8 baffles, and a 0.5″ spacer between the primary blast baffle and the rest of the baffle stack. This gives you a setup similar to the diagram seen in the nomenclature section above. With this setup, roughly 47% of the original volume is retained and roughly 53% is taken up by spacer and baffle materials. Albeit basic, this is a solid high-pressure cartridge setup that might not be the quietest can in the world, but is pretty damn effective.
From here, you can modify the design to be optimized for lower pressure cartridges, like subsonic rifle, handgun, or rimfire cartridges (which require less volume). Let’s cut the spacer tube 1″ shorter and add two more baffles.
As you can see, there is less internal volume, but since you will be shooting lower pressure cartridges, it will need less internal volume for expansion. This would make an exceptional handgun caliber or rimfire suppressor, and an excellent subsonic rifle suppressor.
This is by no means the only way to accomplish effective suppression, but just one guy’s opinion. I am genuinely fascinated by the engineering and physics behind sound suppressors, and I’m always interested in learning something new. If you have any insight or knowledge on this topic, please feel free to comment and share what you know.
Thisguy's Guns 
This is a great article, thank you for posting it.
Now a theory question:
Would a shorter barrel require a bigger expansion chamber due to the excess gasses stemming from the less optimal burn? Or to put it another way would you want a higher velocity suppressor design for a shorter barrel?
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For a shorter barrel, yes, more expansion space will be necessary to make it quieter because much more of the powder will be burnt outside of the barrel. The big issue with short barrels, however, is baffle and tube erosion. Much more of the explosion from the powder charge is burning outside of the barrel, which means much more concussion is happening in the primary blast chamber. To combat this, you’d need to have a fully encapsulated primary blast baffle of a ridiculously hard material, like inconel or stellite, much like SilencerCo’s Hoplon design. This will keep down baffle erosion substantially, but will definitely increase weight.
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Dear Thisguy,
After scanning the internet, I thought you had to have a tattoos, a southern accent, or grey beard and a truckers cap to expound this much knowledge in firearms/suppressors. No disrespect intended to those mentioned as I have ink and from the south. Thanks for a well written and illustrated piece on this topic!
I own several commercial silencers now, but just acquired a 450 Bushmaster on an AR15 platform. I have decided to go Form 1 and build my own suppressor for this weapon. I have access to a master machinist and a personal background in metallurgy.
1. Thoughts on how you might design a suppressor that can maximize recoil and get the noise level down?
2. Access to design drawings?
3. Is there anywhere I can get more knowledge by searching on different terms for the item I want to build?
Again, kudos on your knowledge and ability to communicate!
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Oh man. Sorry to disappoint! I don’t have any ink, my hair is only now starting to get a few greys here and there, and I sadly have a metropolitan Alaskan Accent (hard to describe because… well… it doesn’t sound like an accent to me).
ALBEIT, To answer your questions:
1. I’m assuming you are looking for maximum recoil reduction and quiet. WELL, a conical cup baffle of some sort will help a lot with recoil, but just about any baffle system that isn’t a blow-through (like OSS) will reduce recoil. If you are building a can for .450 Bushmaster, the weight will help with recoil as well. I suggest getting an adjustable gas block as well to slow down the bolt carrier from the extra dwell time a suppressor will add to the system. The conical baffle is used by a lot of players in the industry, so it’s a solid choice, but I bet if you ask 50 experts, you’ll likely get about 1000 opinions on the topic. (please note that I am by no means an expert. I’m just a guy on the internet). Sadly, the reason why there are so many different baffle designs and concepts is because there is no ‘best’ solution. I don’t think engineers have discovered that yet… although, I’d say in the next 5 years or so, we might just have someone figure it out.
2. I don’t have any access to design drawings that you are not. Look for suppressor cutaways, x-rays, and design blueprints for some of the most popular suppressors out there and it will inspire you.
3. I suggest checking out silencertalk.com (if it’s still around). Helpful terms to search for around the internet would be baffle stack, blast baffle design, and suppressor cores. If you really want to go down a rabbit hole, look up a tesla valve. If you get really creative and figure out how to harness that, you might just find your perfect suppressor baffle design. I’m sadly not smart enough to figure that out.
I will tell you one thing, Building a suppressor can be a very rewarding experience, but I learned the hard way that with the money I spent building one out of quality materials, I could have bought one that would have been lighter, quieter, and generally better. Your mileage may vary, but that was my experience.
Best of luck to you!
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Have you ever thought about a secondary layer around the baffles with the screen and insulation system like the old glass pack muffler design? Is lessening the pressure within each chamber between baffles create more, or less suppression?
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A long time ago, yes. For the most part, the less pressure there is between baffles, the quieter it will be. I thought about some sort of insulating wrap to go around the internal baffle structure as a way to slow gases through dispersion. However, the big issue I run into is volume. If I try to add stuff inside of the tube, i’ll lower the overall volume and increase pressure. I’d need a much larger tube to achieve better performance than the basic baffle design I’ve made so far.
I remember reading about some company that made a glasspack like sound suppressor for .22 LR. Apparently it was really quiet for about 10 shots, but was worthless after those first 10 shots.
Actually, it brings back a memory that led me toward trying to make such a contraption. I remember encountering a sound absorbing wall when I worked for the University I went to, and the wall really threw me off. Any time one of your ears faced the wall, it was like something was plugging your ear. The wall itself was made of a lattice-like layered plaster that was super porous, so sound couldn’t reflect off of it. The closest thing I can find to the way it looked is this stuff here called wood wool. That gave me the thought of making a .22 suppressor with a layered fire-resistant lattice that made up the innards of the tube. I was never able to find any fire resistant material easy enough to work with to make the thing, but I bet it would make a fantastic limited-use suppressor.
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Hi there I’m try to purchase one of these inserts for my d-cell maglite An into get the prices
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So long as you’ve got your form 1 approved and tax stamp in hand, you can get cups here:
https://www.jmpf.company/
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Was a great article. Building a 12in on a .22. But with a 1.5 in blast chamber and the rest baffles it doesn’t seem to suppress very good. I rearranged my baffles to there I get more volume for the gases , less baffles and it seem much quieter. Does this seem logical
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Oh yeah, that might work well! Tinkering around with baffle layout can change a lot. What you might be experiencing as well is a shift in tone. With tighter spaced baffles, you might experience a little higher/sharper tone than if you have baffles spaced out more. What kind of firearm are you using as the host? Rifle? Pistol? Bolt? Semi-auto? Also, what kind of ammunition?
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Thanks for your response. Have a Rutger 10/22, ar platform. I have 12 baffles cups and a 1.5 in spacer(blast chamber). 12 in tube When just stacked I can’t hardly tell the difference. So I changed the baffles around to create more space for the gasses to , I guess expand. The sound was hugely more muted. You might be right about the high pitch, I can’t hear the greatest, but was very impressed afterwards So I’m building a 9mm pistol with a 5in barrel with the same 12in tube with a 2 in blast chamber followed by a baffle and then a 1.5 chamber necking down. Trying to make it kinda look like a bull barrel. Any suggestions?
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That’s an interesting design. Are you machining the parts yourself? You might get some interesting results from a big expansion chamber, then necking down to something more bull barrel sized. Almost like a Russian PBS-4 suppressor, maybe? I think the most that might happen is you might see a little extra back pressure from the stepping down in internal diameter, in that fluids will gain velocity when stepping down… I think? It’s been a while since I took physics, but I think that’s similar to how rocket engines work.
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Hey man! I was wondering if you have a design for a 5.56 suppressor, like a blueprint or something?! Maybe you can help me build one.
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>*First, please make sure you file all of the proper paperwork and have the approved BATFE form 1 and tax stamp IN HAND before even starting construction*<
The high pressure/high velocity suppressor diagram I've got on this blog post will work fine for 5.56. The key is to use a very hard material for your Primary blast chamber and primary blast baffle. That should help keep baffle erosion down substantially. You can repurpose Stainless Steel D-Cell Dry Storage Cups for a primary blast baffle. The more volume in the primary blast baffle, the safer the can will be. You can form steel freeze plugs into M baffles, and that can finish the rest of the baffle stack. Also, The more concentric you can make the baffle bore, the tighter you can make the bore diameter, and the quieter it can be. If you have access to a lathe, getting bore concentricity will be simple.
I'd try to help you through here, but there are lots of forums and tutorials easily found online that would be much more helpful than I could ever be. Good luck!
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Very good post. Supressors are a science and engineering treasure trove, love them. You forgot to mention something very important. Vacuum pressure causes a good amount of air to continue to follow the bullet past the first, second, third (etc) baffles. This is why SWR (SilencerCo) has a nice, albeit smaller, chamber at the end of the baffle sections. It is also why they have two mid sized chambers after the first blast chamber/baffle. It allows that air/propellant mixture following that boat tail bullet to have a greater chance of being caught before exiting the tube. Those extra volumes in those places allow propellant to finish burning/lowering pressure in that last section.
There is also another characteristic on the SWR suppressors that you should point out, look at the shelf after the radial curve of the baffle. They are nice 90 degree angled corners and on the first sets of baffles the radial ramp goes straight to them. This forces the pressurized gas to slam right into the corner and fold in on itself, into the other 90 degree shelf corner and back into the void in the chamber. The baffle angle changes as it goes down and then causes a swirl to reverse flow forcing the gases back into the first baffles. This is a good design and optimizes the energy dispersement to counter itself as much as possible before leaving. Which is ultimately the name of the game.
This is something overlooked by some form 1 designs that use M or B baffles. Those rounded sections (where your arrows are pointing on your diagram) cause gases to swirl back into the projectile path and it continues to move forward and eventually out of the suppressor before it has lowered its pressure. Baffle design makes a huge difference and can lower the volume necessary.
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Yessssss! This is why if find the science so fascinating. Even the subtlest nuance in the suppressor design can have huge impacts on performance. Had I machinery to make proper baffles, I’d probably have designed it with a much more aggressive taper on the baffle, and a flatter wall at the front. Good info, man!
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It is NOT necessary to furnish a diagram of a silencer/suppressor with a Form 1.
Block 4(a) says:
Name and Location of Original Manufacturer of Firearm
(Receiver) (If prototype, furnish plans and specifications) For a RECEIVER FIREARM, not a silence/suppressor.
For a Form 1 silencer you put Your Name, Street Address, City, State and ZIP Code.
Block 4(b) will say SILENCER
Block 4(c) Caliber or Gauge (you put like 5.56mm., or .223 or 30 Caliber or whatever)
Length
Block 4(e) is N/A
Block 4(f) Overall (longest length you expect it to be, if ends up shorter is no big deal)
Block 4(h) Your Name, City, State (2 letter Postal Code is acceptable), Model (optional), Serial and Caliber.
I have 2 Approved Form 1s for a Silencer/Suppressor and did not submit drawings.
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This is very good information. I totally thought I needed to furnish a design for a prototype suppressor. Thank you for the clarification!
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I have built two 300 Blackout rifles for hog & coyote hunting in Alabama. I have thermal on one and IR on the other. I want to construct two licensed suppressors. My present intent is to have a primary blast chamber approx. 6 inches which overlaps barrell, and stacked freeze plugs for about 5 inches of extension past 16 ” barrell. Thinking of titanium outer tube and modular assembly. Not threaded ends. I am an engineer/lawyer and can fabricate about anything. I would truly appreciate your commentary on my intended design.
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What you are describing sure sounds a lot like a reflex suppressor. I love those designs! I originally had an idea of doing something similar, but having the affixment point at the gas block with an internal index on a muzzle brake to keep the suppressor bore concentric to the barrel bore. The muzzle brake would also direct primary gases rearward to expand into the reflexed portion of the can. Wait… Sorry, I have to stop for a second to calm down…
I think this is probably one of the sexiest designs that any suppressor could be. Since I’m not a machinist, nor have I ever had access to one, I was never able to make a gas block with forward facing threads to make one of these. My god, I want one though… I bet it would be super effective and look like pure, unfiltered sexy.
Now, making it without threads has its set of challenges. I imagine if you can get a proper interface, like an H&K 3-lug or similar, you might be able to get a proper seal. What do you have in mind?
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Thanks for naming my concept as reflex. Found some. That’s it! I have a copper tube which tightly fits outside of bbl at 0.75 in.dia. It will be crimped to pinch behind flash hider and cover inside of reflex. Copper will silver solider to a forward-facing steel freeze plug bored to fit over bbl. I am going to attempt to attach outer tube to rear plug with multiple external screws. Another set of screws around end of flash hider will also be threaded into a freeze plug which is welded to the end of flash hider.Baffle stack will be secured via steel rods welded to keep them spaced and into alignment. This assembly will be easy to clean or tweak. Baffle Assyrian mounts when flash hider is tightened. When outer tube is installed over baffle assembly and both sets of screws installed, whole suppressor is reliably bore-centric. My OD of tube is close to the OD of quad rail and fits so close to end of quad that it allows a sliding pin to keep tube and flash hider from turning from installed position and loosening from repeated use. Since I have a special night-hunting purpose of use, I should benefit from easy take-down and cleaning between hunting excursions. After all, my battery’s will have to be removed and charged after each hunt. Suppressor service can be just another item on my prep list.
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Sounds like it’s going to be heavy, but pretty legit. I’d be interested to see how that copper tubing will do over time. I imagine you might see some permanent expansion, and potentially flowing, if it gets too hot. The worst that might happen, which isn’t bad, is that it squeezes tighter against the barrel. I wish you the best of luck and good harvest!
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Good discusion on baffle angle of incidence above. Thanks.
You have probably played with the volume ratios (ref. 47/53 %), have you thought about drilling small holes/slots radially in first series of baffles to increase the volume for expansion?
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I did think about it. What worried me about doing so was disassembly and maintenance. My freeze plugs were widest at the bottom and had a slight inward angle up to the shoulder. This made the base of the freeze plug the effective seal as a baffle, and if you cut holes radially, you wind up losing the seal. Now, having a perfect seal in the first few baffles isn’t really necessary for function or performance, but it sure makes it easier to take apart and clean. If you have radial holes or cuts in the baffle, that’s room for carbon fouling to cake into the cuts and bond to the inner tube of the can. That could potentially lock the baffles into place, and that is no bueno. I imagine it would increase suppressor effectiveness by freeing up volume, but I’ve already had to hammer out my baffles a couple of times and I can’t imagine what it would be like having them get seized up in the can from carbon buildup. I might wind up destroying my suppressor trying to get them out :(. If you have a little wiggle room in your suppressor, it might be worth trying. Mine is kind of tight, so I probably won’t.
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I have a FP form 1 suppressor ready to.assemble. I am still unsure about adding spacers, how many and where in the stack. Also, should the blast chamber and spacers fit as snugly as the freeze plugs. Any assistance would be greatly appreciated. I have form 4 suppressors, but this is my first build.
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Just like the rest of the baffles, the primary blast chamber doesn’t have to be friction fit, but the more snug, the better, and concentricity is key. If you need to shim, I’ve used parchment paper before to shim around the spacer tube that makes up my primary blast baffle. It’s not a permanent fix, but the parchment paper holds up to heat exceptionally well. After shooting for a bit, the can will fill up with carbon and really tighten up all of the little gaps, so don’t fret too much.
As for spacers, like I discussed in the article, it will depend on the dimensions of your suppressor and your intended application. I am no expert, but I can provide some opinion on the topic. If you are planning on using the suppressor for high pressure applications, you may need to add an extra expansion chamber, like a secondary blast baffle, for expansion volume. This would involve adding a section of spacer tube between the primary blast baffle and the rest of the baffle stack. If it’s a lower pressure application, you may not need any spacer tube at all. After the primary blast chamber and primary blast baffle, just stack the rest of the baffles until you run out of room. If you are having issues with your internals moving around inside of your can while it’s assembled, then I’d suggest adding a spacer of some kind to the muzzle end of the suppressor to tighten it up. I wound up welding a washer to the last baffle to tighten up about a 1/16″ bit of play I had in my suppressor. Your solution might vary
Once again, this is just opinion. These are the two setups that I’ve used and both work well. Also, be sure to take a look at cutaways and x-rays of factory suppressors for inspiration. Get informed, get inspired, and get creative.
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What, in your opinion, would be the best baffle placement for higher pressure rimfire like 17HMR and 17WSM?
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Well, rimfire, by nature, involves a lot less pressure than most centerfire. Even .17 WSM, with a max pressure of 33,000 P.S.I., is still under the max pressure of 9mm Luger (35,000 P.S.I). You can run a handgun design with any rimfire and get good results. Just know that the supersonic crack will still be pretty darn loud, but the initial report will be significantly less.
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A very basic question: Is an optimized gun sound suppressor simultaneously also an optimized recoil suppressor?
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From what my research and experience has taught me, yes. An effective suppressor also acts as an effective muzzle brake. It does this for two reasons:
1. The weight of the suppressor adds weight to the gun, thus slowing down the recoil acceleration.
2. The redirection of propellant gases pushes the entire gun away from the shooter, thus slowing down the recoil acceleration.
I’ve heard from a SilencerCo representative that one of their suppressors reduces recoil up to 40% on some calibers (I don’t remember which one). I will agree that shooting my 6.5 Creedmoor with my SilencerCo Harvester 30 attached does have considerably less recoil than shooting without the suppressor. Whether it is or isn’t 40%, I couldn’t tell you, but the difference is significant.
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Some time ago I remember reading or hearing the above suggested logical statement via a question, which succinctly related this additional advantageousness for using a suppressor, but my recent recall & search for further & current confirmation has not revealed any cognizants in the suppressor-action area & I’ve been mystified! One would think that the pro-suppressor- group (including the manufacturers of both suppressors & guns) would be relating this wonderful additional plus happening of recoil reduction? In fact, I can’t imagine any gun manufacturer of the larger bore guns (the ones that are used on dangerous-to-hunt large game) that hunters typically don’t shoot much to get good shooting with them, because they’re so punishing to the shooter via both noise & recoil. Thanks for the positive confirmation!
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I am noticing a shift in POI while the suppressor is attached vs not. The change is repeatable. I am not seeing baffle strikes. The shift of POI is more than I would want to change the scope settings . Any advice would be appreciated. This is on a 22 LR rifle.
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I’ve noticed this too, even with professionally made suppressors, but it varies widely with bullet weight and shape. A prime example being that I have a Ruger American Predator in 6.5 Creedmoor, and it shoots the Hornady 129gr American Whitetail Ammunition. When I put my SilencerCo Harvester 30 on it, though, the impact shifts downward considerably (like 2″ or so) and the groups open up about an 1″ or so more than usual. I assumed that it had to do with the suppressor changing the barrel harmonics, causing the barrel to whip differently. HOWEVER, if I shoot the Hornady 140gr American Gunner Ammunition, there is zero point of impact shift and zero group size change with or without the suppressor. It’s really blowing my mind a bit. I need to do some serious research on it because I’m thinking the bullet weight and shape might impact how the turbulence within the suppressor interacts with the projectile during its travel through the suppressor…
I also see extreme shifts when using my 9mm form 1 suppressor on the MPX. We are talking 12 inches of change with 115gr bullets, but little to no change with 148gr projectiles… I’m baffled myself…
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I may try opening up the passageway in the baffles to a larger diameter. Currently they’re all drilled at .250. I’m also changing the spacing on the baffles having the first one the blast chamber being the longest. I think that it’s got more to do with turbulent gases in my situation than it does with barrel harmonics being only a 22 Long rifle. I greatly appreciate your reply as I envisioned my comments just going into cyberspace. The physics involved are truly amazing.
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I greatly appreciate your reply as I had figured my comments were just going to cyberspace. I’m wondering if the shift in point of impact isn’t more correlated to the swirling gases within the suppressor device prior to exiting of the projectile. I’m only using a baffle system that will have a 90° affect on the gases as opposed to the more streamlined tapered baffles. I am changing the spacing between the baffles and adding a longer initial blast chamber. Thanks again for responding.
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When my device is mounted on my GSG the POI is the POA exactly. Put that same device on a 10/22 and it’s a crap shoot. I noticed that unscrewing the device 1/8-1/4 turn would bring the POI back to POA on the rifle. No baffle strikes just inconsistent POI.
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You know, I’ve done a little bit of research on this, and it appears that this is not an uncommon issue with 10/22 rifles. I think someone out there makes a 1/2×28 threaded spacer/lock ring to address this issue. From what I’ve read, it’s because the shoulder where the threads end on the muzzle of the 10/22 may not be perfectly flat, so a lock washer might be needed to establish perfect concentricity. Be careful with that 10/22, though. A buddy of mine threaded on a SilencerCo Octane 45 and got a baffle strike using a 10/22 just recently. It was a pretty brutal baffle strike, also… I don’t wish that upon anyone.
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Recently built a form 1, maglite style suppressor. I like the SD tactical titanium barrel shroud and mounts best. Had to build a face spanner wrench using hi-locks with the heads filed off in the drill press. And J&S tactical freeze plugs are the best to form baffles from IMHO. Blast chamber spacer is 1.375 OD 6061 sanded to the correct diameter on a mandrill in the drill press using a Dynafile. Drill press is the fanciest piece of machinery I own.
One thing I did different than anything that I have seen anyone else do is in the way I formed baffles. My baffles are swaged backwards to what you usually see. Drilled the baffles with the standard baffle drill guide. Then found that I had to drill the hole out to 3/16 and deburr or when swaging they would crack badly. But a 3/16″ hole works fine. Used the General swage tool to swage that 3/16″ hole out to .400″. This swage tool is a single ~8″ polished steel shaft that steps incrementally from 1/8″ to 5/8″ and cost about 10 bucks. For a swage block, drilled a 2″X4″X10″ piece of oak. Starting with 3/16″ drilled progressively larger holes every 1.5″ down the 2″ side and countersunk the holes @ 82° progressively deeper. Set the swage tool in the hole in the baffle and drove it with a ball peen hammer into the swage block. Progressing down the swage block an avoiding getting the tool stuck in the hole, going along until the hole is .400″. Swaging this way makes a baffle that is sharply turned “duck face” at the lip.
One problem that no one seems to admit is fitting. Unless you get your spacers perfectly sized your suppressor will rattle. Not good and it is difficult to find the right washers for the job. I made my own washers. Took 6061 sheet and with a 1&5/8″ hole saw cut out a hole. This cut hole will be a little less than 1.5″ in diameter. Cut 5 of these holes and then put them on a mandrill and turned them down to 1.36″ in the drill press. Clamped a piece of 1X4 to the drill table and drilled a 1/4″ hole. Took out the 1/4″ drill bit. Put a bolt up through that hole in the 1X4 and put one 1.36″ 6061 hole on the bolt, then a washer and snugged down a bolt. Put a 1″ holes saw with no center drill in the drill press chuck. Hole saw will chatter but makes a washer that is 1.36″ OD and ~1.0″ ID. Requires some serious deburring.
I do have one question: Has anyone determined the optimal number of baffles and spacing for a 10″ long, center fire, direct thread, maglite suppressor?
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You know, to solve the rattling suppressor issue, there are a few routes you can take.
1. You can use the battery spring from the maglite to add tension inside the suppressor at the muzzle end.
2. You can find a washer that has a somewhat similar OD to the ID of the can to use as a shim, and hone it down flat until it fits perfectly snug when fully assembled. This is time intensive, but it works.
3. If you have access to a cheap stick welder, you can add little nubs of steel to one of the baffles, then hone them flat until the baffles fit tight when fully assembled.
As for the optimal number of baffles, that is to be determined. I’m not sure the professionals have that figured out quite yet, but I’d highly recommend looking at cutaways of various suppressor manufacturers’ cans and see if there is a trend on the number of baffles vs effective suppression.
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Fantastic article and discussion. Thanks!
I’m a newby and have a question. I’ve built a suppressor for a .223 rifle. Fired a few shots from a previously zeroed ar15. Suppression quality was good. Did not need any ear protection. However, the problem I’m having is that at 10 yards the rounds are hitting 2 inches away from zero. I thought there may be a baffle strike, but the baffles are clean / no damage. Any idea from anyone on what is causing the problem? Thanks in advance!
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Hi Gary,
What you are experiencing is called Point of Impact Shift, and is very common in the suppressor world. I think the issue is pretty complex and has several contributing factors. The common factors are:
1. Asymmetry in the suppressor components.
2. Baffle shape and geometry.
3. Altered barrel whip and vibration nodal points from the addition of the suppressor. (shifted barrel harmonics)
4. Added weight from the suppressor changing barrel direction slightly.
5. Turbulence inside of the suppressor causing the bullet to go slightly off course.
6. Inconsistent or not-square mounting method.
These are just some contributing factors, but truthfully, the science is well above my comprehension. Professionally made suppressors tend to have little to no point of impact shift, and they probably keep that secret safe. I think all form 1 suppressor builders struggle with this. I have substantial issues with it using my form 1 9mm suppressor. I imagine that if I had more precise tools, I could reduce point of impact shift… but since I don’t have said tools, I’m stuck with what I’ve got.
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We have lengthened the 1st baffle bore to 5/8″long, then tapped a 3/8 coarse thread into this bore, (308) This further disrupts gas flow from the blast chamber to the baffles. The end cap has been treated in the same manner. Full power loads are reported by a third party to be ’22 magnum rimfire” like. Sorry you have such a restrictive rule on these devices.
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Have you thought about using the handguard as a suppressor? Say you have a 9mm AR pistol with a 5″ barrel, and a solid tube handguard around 9″ long. The end cap wouldn’t be too hard, but the baffles i was thinking you could thread into position. I saw a company make an integrally suppressed barrel where they threaded baffle stacks down into the barrel. You could do something similar here to get the baffles into place. That company said that after a couple shots from the weapon, the carbon buildup was enough to hold the baffle stacks in place so they didn’t move or rattle. You may have to make the holes in the middle of the baffles/end cap larger to accomidate the fact that it’s not attached to the barrel. This should give you a ton more volume than you normally could get. It would also allow you to port the barrel to lower velocity of standard velocity bullets down under the sound barrier for quieter operation with bulk ammo.
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I dont think it’s a good idea to leave this on here.
You forget 3d printing technology and its use by criminals, these days, everyone can 3d print a gun that can fire a shot or two, which is enough for nefarious ends.
What do you think will happen when people doing these things not only have the exact shape for more effective supressors readily availeble through the images, but also the the main theory behind them and their function in layman’s terms provided by someone who likes to delve deeper into these things…
You might have thought that a sustainable multi use gun was not viable when you made this… But you are essentially handing a guide for a single use supressor to people here…
Its up to you if you leave this on but… I want you to consider the consequences of sharing your enthusiasm like this…
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Absolutely not. This article will stay up because this is only the sharing of information and opinion. What you are implying is alarmism, with the intention of suppressing information through fearmongering. While the exchange of information remains free on the internet, so shall this article remain.
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Sorry I could not figure out how to post this question directly so I am replying to your latest comment. Got my permit after 6 months and built my suppressor for my 9mm CZ P-10 C. Sound reduction is good, but the shell does not get ejected. I tried a friend’s Silencerco 40 Osprey and it works perfectly. Mine weighs 10.2 Oz, the Osprey 10.7 oz. Any suggestions?
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I’m assuming you’ve got a nielsen device (a booster piston) on your form 1 can. I anticipate that the problem is that the can is so heavy that even with the nielsen device in place, it still doesn’t have enough recoil energy to cycle the action. I have the same problem with mine, so I gave up on using it with short-recoil operated firearms (like most semi-automatic pistols). You can continue to try, but try lubing up the spring mechanism in the booster assembly. That does help a little bit. You can also try to find a slightly lighter spring, but you might risk it not resetting properly and losing concentricity.
If you have access to a camera with high-speed capability, like 420fps+, you should film the gun shooting from the ejection port side with a clear shot of both the ejection port and the threaded end of the barrel. Look to see if you are getting a full extension from the booster before the suppressor itself begins to move. If it does get full extension and still doesn’t cycle, it might just be too heavy.
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Richard,
Does the suppressor you built have a piston on it? I actually have your exact setup and I built mine with the Griffin piston on the end. As long as the spring is oiled properly it runs like a champ, and just as good as my Osprey 9mm. There are some target ammunition with lighter powder loads that wont cycle a suppressor..
If you dont have a piston, go get one and try. As well, you should get ahold of different ammunition loads of 9mm, including +P loads a d test.
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I have a thought idea relative to the making of a dual functionality for a gun that could make the advantageousness of a semi auto & also the advantageousness of a bolt action gun be selectively available on the same gun. This dual capability is desired because while a semi auto’s fast follow-up shot is wonderful when stopping a charging beast, it does have some disadvantages when all one desires is an optimum quiet single shot that doesn’t have the chambering noise for the ejection of the fired shell & the loading of the next round, as well as a desire to quietly & efficiently save the casing for another reload. Of course, a bolt action gun is inherently the optimum gun when the beast charge isn’t happening & the noise of ejection & the loading of the next round isn’t needed to happen in a rapid sequence. Also, the bolt action allows the handling of the spent cartridge case to safely save it for a reloading, by keeping it off the muddy ground in a location to-be-determined after a time consuming search….as well as avoiding the bagging noise of the spent case, if it were to be captured in an ejection case bag.
All that would be required would be a action lock-pin for the semi auto to keep the action locked until the shooter would desire to manually eject the spent case & to insert the next round at a desired timing to suit the environmental conditions of his slow sequential shooting! This would also handle the variable powder loading the does & does not supply enough gas to auto eject the empty case.
Duane Sprague
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Hi, I have a couple questions as far as design ideas.
How are you incorporating the Nielsen Device into your build? I don’t see it in any of your drawings, and from what I’ve read it’s needed for correct operation of any pistol with a moving barrel design. Is there a type of addon that can be used, or do you have to design one from scratch?
When considering the difference between low pressure and high pressure cartridges, what is the advantage of putting more baffles in for the low pressure? In other words, why not just use the same design(larger expansion chamber) with a pistol as you would a rifle?
Lastly, and this is just my own curiosity here, has there been any research done into the placement of the expansion chamber? IE: is there any difference in whether the expansion chamber is before, after, or in the middle of the baffles.
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Good questions.
Yes, in order to use a suppressor on a handgun that uses a short-recoil operating mechanism (like Browning style tilting unlock, Walther P-38/Beretta falling block type, etc.), you’ll need a Nielsen device. There are adapters you can find online that convert the D-Cell form 1 tubes to a thread pitch that works with Liberty Mystic or Gemtech booster assemblies. I can’t remember what the thread pitches are, but I do remember that I had a hard time finding them online. However, the adapters are around. I have one I used for an H&K 3 lug adapter for PCC use that also had the same threads as the Liberty Mystic booster assembly, so they do exist.
As for the design differences between the low pressure and high pressure designs, what I write about above is mostly theoretical in nature. I’m taking the information that I see in professionally made sound suppressors and trying to make sense out of it. The reason I think for the greater volume in high pressure designs is due to the fact that they simply have greater amounts of propellant gasses to slow down. The advantage of having more baffles in a low pressure design is to create more turbulence inside the can to slow down the propellant gasses (therefore making it quieter, theoretically). It’s ideal for a suppressor to have as much volume and as many baffles as possible. It’s all relative to work space, I suppose. I mean, like I said, I’m really just basing this off of what I see from professionally made cans. Pistol cans tend to have more baffles and rifle cans tend to have more volume. You are free to experiment, so you might try new and different configurations and find a beautiful sweet spot.
Finally, as to the expansion chamber which is where you find the primary blast baffle, from what I’ve been able to gather, has to do with concentricity from the initial release of gasses once the projectile leaves the muzzle. The idea is that if there is perfectly concentric force applied to all sides of the projectile as it leaves the muzzle and travels through that first primary expansion chamber, there will be little impact on the projectile’s flight path. By lowering the pressure immediately, it also lowers the likelihood of those initial propellant gasses imparting eccentric energy onto the projectile. Better concentricity = better accuracy. NOT ONLY THAT, but the more room for expansion means less pressure. Less pressure means less stress. Less stress means less wear on your primary blast baffle. Less wear on your primary blast baffle means longer suppressor life. Longer suppressor life means happier you! I think you get the idea.
All in all, there is nothing here you cannot experiment with. If you want to try something new, try something new! It’s all part of the fun of form 1 suppressor building.
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Almost forgot, what are your thoughts/findings on designs that use wipes?
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Wipes are interesting, but have detrimental impacts due to 2 things:
1. the bullet has to physically touch the wipe for it to be effective, therefore it will hinder accuracy. If it’s just overall sound suppression you are going for, it works great. If you want to hit things with repeatable accuracy, not so much.
2. Wipes are considered suppressor parts by the ATF and you can get in trouble for making more (I will leave it at that).
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Thanks for your reply. Given me some things to think about.
I actually went through and re-read your article, and got fixated on the Tesla valve. (I often get fixated on his inventions whenever they’re mentioned). After some preliminary research, and a few YouTube videos, I’m wondering if the same effect can be achieved by drilling holes near the outer circumference of every other baffle. In theory(read, in my head) this would cause the expanding gasses to pass through the drilled baffle and be diverted backwards by the baffle left intact. Thus further slowing the gasses in the same way as Tesla’s valve. It may not be quite as effective, as it seems his is designed with a slight curve to the middle passage rather than the straight shot we would require. But it seems doable. Thoughts?
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I have had the same thoughts on the holes to act in the same fashion to create turbulence. My question, which would help in the hole placement is, what is the velocity of the gas after it exits the barrel and is not impeded by the bullet. I cannot find anything on this as of yet.
If you watch the super slow motion of a bullet existing a gun, the gas will go faster than the bullet.
My fear is locating the holes to close to the bullet apertures may destabilize the bullet by directing perpendicular forces on the bullet. By knowing the exact location to place the holes to cause turbulence at the optimal time might achieve a Tesla like impedance in the flow. Unfortunately, with form 1 design/ builds, you cannot modify or repair the silencer once it is completed. In other words, no test builds are allowed.
Once again, can anyone point me in a direction to find the velocity of the gas once it is no pushing the bullet. I realize types of gunpowder’s, calibers, and lengths of barrels would all be variables.
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Have you read “Silencers – Principles and Evaluations – 1968” by the US military? There is a brief section in the back detailing many ways that can be used to increase the decibel reduction of silencers. It also has math.
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I HAVE NOT! I didn’t even know it existed… then again, my research was pretty limited to what I could find on the interwebs. I think I’ll try to see if I can find at copy somewhere and give it a go through. Thanks for the info!
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Hey
Great write up. I may have missed it in your article or the info wasn’t there. The one question I have is what are the mouse holes for? As in the MP5 SD. All the baffles have a notch running perpendicular to the orifice that the projectile travels through. What would those mouse holes do for the flow of gasses or do they serve a different purpose? Are they required?
Thanks
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Good question. What you are referring to, I believe, are what in the industry they call ‘Clipped Baffles’. I’m not 100% sure on the purpose, so I can only postulate. However, I believe it does have to do with pressure relief and turbulence. I can guarantee they are not required, but definitely do something.
For example, I’ve got a SilencerCo Harvester 300 and an Octane 45HD. Both of the same generation and both have clipped baffles. I’ve seen them a lot, but not exclusively, in high-pressure, centerfire rifle suppressors. WITH THAT SAID, I’ve also got a Hybrid 46, and I do not believe that has clipped baffles… weird, huh?
There are a lot of effective designs out on the market currently that use them, so I can only assume there is a functional purpose. Since I’ve not experienced any significant point of impact shift with the loads I shoot, I’ve never tested to see if timing the clips made a difference. That might be worth exploring.
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Wow I’m impressed this is still going, I am working on making a sort of Working Replica for a game gun from Destiny. I think I have everything sorted except that the barrel has a conical “bulge” for lack of better term right after the front sight area of the rail. I know my old M-16 and M-4 had some variance of this but nowhere near this level of overblown proportion so I was curious if a “custom” suppressor could use such a design to any successful effect? For details I am thinking about using a 16″ barrel with a 1:7 twist and for a reference image it’s called the khovostov 7g-OX. All of this to be honest is making me want to get into custom working replica work so feel free to get as deep in the details as you’d like.
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Looking at the gun’s image, it looks quite similar to a PBS-1 Suppressor, with a locking collar in the back, but having a conical taper off of the locking collar. You can do anything you’d like, so long as you have the machining prowess to do it. It also looks like a 10″ SBR would give a closer to the original look, but if that’s not possible, you can always make a reflex design that goes over the front 6″ of barrel like a shroud. Would be neat.
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You have certainly tweeked my interest.
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