Part 1 covers the parts, tools, and steps required for building a suppressor. Click here for Part 2: How to E-File ATF Form 1. You must file Form 1 and receive approval from the ATF before building a suppressor.
Suppressors are over-priced, and the ATF is way too slow when it comes to processing Form 4 applications for ownership. That Gemtech or Surefire (yeah, the one with the $1,000 price tag) that you’ve been drooling over? It ain’t worth that much, Jack. And it certainly isn’t worth waiting 12 to 18 months just to take the damn thing home. No worries. You can reliably build your own suppressor with simple tools and parts, and you can get the ATF to do your bidding and process your application to build a suppressor in about two to three weeks.
The finished product will perform just as well as or exceed a retail-purchased silencer, too. We’re not talking about Wix oil filters or Chinese “fuel filters”, either. We’re not covering some gimmick that could blow up on you or land you in prison. Part two of this project will cover how to legally finish this project by filing some electronic paperwork and fingerprints with the ATF. But that’s not as exciting, so let’s focus on the fun part. Here’s how to build a quality, homemade suppressor with little to no knowledge, and just a few basic parts available from various retailers.
How a Suppressor Works
It’s important to know how a suppressor works, first. A big part of this project involves cutting or drilling the right components to ensure your homemade suppressor provides adequate noise reduction without exploding or failing.
A suppressor’s job is relatively simple: Capture the gasses exiting the muzzle of your gun, and contain them long enough to slow them down. The suppressor does this by creating turbulence. That turbulence is made by forcing the gas into small pockets, cones, and cavities. These are created with baffles. The longer all that gas has to expand and slow down before exiting the suppressor, the quieter the gunshot will be.
Now you know the basics. It really is that simple. Onto the construction part. A suppressor’s made with three components:
- The tube or “can”, which contains the baffles.
- The baffles, which slow down the gas inside the tube.
- The end caps, which contain pressure and secure the suppressor to the muzzle.
The baffles slow the gas down, creating all that turbulence and reducing velocity. The tube and end caps contain the gas, preventing the explosion and sound inside from escaping. The energy your suppressor’s working to contain is incredibly high. That means your suppressor’s converting a lot of energy into a lot of heat. That means you need quality alloys, like stainless steel, high-grade aluminum, and titanium. That leads us to the first section of the build itself:
Building A Suppressor: Materials Required
- Metal Tubing
- End Caps
- Adapter (if not directly threading to muzzle)
Option 1: Buy Material from Scratch
Stainless steel and 7000-series aluminum work well for making your own tubes, baffles, and end caps, and basic 4000-series carbon steel provides an affordable alternative. Steel is heavy, so many builders combine these two alloys and some use titanium if they have the right equipment to cut and drill it. If you opt to buy the tube yourself then you’ll need tubing with a minimum wall thickness of .06″ for centerfire rifle cartridges like 5.56 NATO and .308 Winchester. If you’re shooting a magnum rifle or big rounds like .338 Lapua, minimum wall thickness jumps to 0.1″.
Option 2: Buy Solvent Trap Components and Fabricate Them
If you’ve ever heard of the 80% lower for the AR-15, then you’ll find the concept of the solvent trap relatable: Solvent traps are normally used as heavy-duty cleaning accessories for your rifle or pistol. Traps thread to the muzzle of a firearm with a tube and end cap. Inside, they often come with a series of cups and filters (also called “cones”) to capture those poisonous and corrosive solvents and cleaning chemicals. Conveniently, these internal filters and cups are often made from high-grade aluminum, stainless steel, or titanium to resist corrosion. These “internals” are also perfect for cutting and drilling some improvised suppressor baffles. Take a look at the example below:
Solvent traps like the 5.56/.30-Cal Kit pictured above include all the components you would need to cut and drill raw material and modify the trap to instead function as a suppressor (once you’ve filed the appropriate ATF paperwork, of course):
- Stainless steel (SS), Aluminum (Al) or titanium (Ti) tube.
- Stainless steel (SS), Aluminum (Al) or titanium (Ti) solvent cups.
- Spacers, to separate and stack the cups if they aren’t “skirted”.
- Threaded and sealed end cap to prevent chemical spillage.
- Threaded open end cap for attaching to muzzle.
The only work you would need to do to the solvent trap above involves drilling pass-through holes in the solvent cups, turning them into baffles that a bullet can pass through. It’s incredibly important the diameter and location of the holes you drill be precise. If the holes are too wide, the suppressor won’t capture and dissipate all that pressure (and sound) effectively. But drilling holes with tight tolerances means they need to be incredibly precise, lest you wind up with an exploding suppressor because your first bullet down the tube struck a baffle or ruptured the tube. So, how do you make precisely machined holes? Many machinists and hobbyists use a lathe or drill press. Even without any tools like that, you can simply use a machining jig like the one below:
A jig includes a small centering fixture and a plate with a drill bushing with the correctly sized drill bit. This jig setup allows you to automatically find the center of the cup to drill the pass-through hole. A drill press or even a hand drill and vise can be used. All you need to do is secure the cup and jig assembly together with screws. Then drill through the baffle via the jig with the included drill bit.
Since the jig controls the bit’s position, all you need to do is control the drill.
Drilling The Baffles: Drill Bit Sizes vs. Caliber
- .22-Cal: 9/32″
- .30-Cal: 3/8″
- 9mm: 27/64″
- .40 S&W: 15/32″
- .45 ACP: 33/64″
- .450 Bush: 17/32″
- .458 SOCOM: 17/32″
- 6.5 Grendel: 21/64″
- 6.5 Creedmoor: 21/64″
- .338 Lapua: 13/32″
- .50 Beowulf: 9/16″
Before you go drilling holes into some solvent trap cups, you need to figure out which design works best for your weapon. Let’s review the common types of cups and cones and what they’re best used for.
Available types of cup or “cone” designs
Skirtless Straight Cone (60- or 50-degree angle)
The skirtless straight cone is most effective in centerfire rifles shooting supersonic ammunition. These are used most often for calibers like 5.56 NATO, .308 Winchester, .300 Win Mag, and similar cartridges.
Skirtless Radial Cone
Radial cones are effective “hybrids.” They work well for centerfire rifle rounds and subsonic pistol or carbine rounds. Most commercial suppressor manufacturers use baffles with a similar design. These are most often used on guns that can fire both supersonic and subsonic ammo, and are commonly favored for 300 Blackout and 9mm Parabellum cartridges.
K-cups or K-baffles represent an older design. They stack directly atop each other and provide excellent performance for handguns, pistol cartridges, and exclusively subsonic rounds. If you’re building a setup meant for a 9mm handgun, .22 LR, or 300 Blackout shooting only subsonic loads, this is a top choice. These internals can also be the most difficult to machine since they require additional machining beyond simply drilling pass-through holes, so they may not be favored for first-time builders or those without a milling machine or lathe.
Freeze Plug-style Cups
These “freeze plug”-type cups are the most affordable, arguably the simplest, they’re highly stackable, and they’re versatile. They’re the “OGs” of the form 1 suppressor world and were used long before manufacturers began producing newer styles like the options listed above. They can generally be drilled for any caliber up to .308 Winchester and provide good performance for a wide variety of supersonic and subsonic loads. Before different options became available, this was the top choice for most Form 1 suppressor builders.
You can find many of the cones listed above with a skirt, or pre-fabricated spacer machined directly into the cone itself. This eliminates the need for buying or cutting spacers.
There are various other types of internals made for form 1 builds, though the options listed above are the most popular and comprise a majority of configurations for most calibers, including both centerfire and rimfire rifles and pistols.
‘Clipping’ The Finished Baffles
Unfortunately, drilling the pass-through holes on your cups, turning them into baffles, and stacking them in your tube isn’t going to provide the best sound reduction. A best practice that is effectively required to achieve the most decibel reduction, called ‘clipping’, must be done to each finished baffle to ensure sufficient turbulence and disruption of laminar flow is achieved to reduce pressure and sound. This illustration below shows how clipped baffles perform compared to un-clipped baffles:
Thankfully, an effective clip is easy to achieve with basic powered hand tools: Cut half the pass-through hole horizontally by a height that is one-third to one-half the diameter of the hole. The finished cut should look like this:
Once drilled and clipped, how well does a homemade suppressor work? Do these setups provide the level of sound suppression offered by a branded silencer you simply purchased from an FFL? Here’s a decent audio comparison. Credit goes to Youtube channel Slammin Hawgs for their recent upload. These guys constructed a suppressor exactly like the example shown in this guide under “Option 2” and ran some 5.56 NATO through it:
The shooter is capable of safely firing his bolt-action with no hearing protection. The Quiet Bore solvent trap, once fabricated and modified, manages to substantially mitigate the sound produced at the muzzle of this 5.56-chambered bolt gun. For an easy sound comparison, here’s popular shooter and instructor Colion Noir test-firing an AR un-suppressed and then with a typical off-the-shelf can of a similar size and diameter:
The homemade suppressor, especially when built from a modified solvent trap, can operate just as well as (and perhaps even better than) a comparable retail suppressor. This shouldn’t be surprising, though — options like the Quiet Bore kit use can accommodate a modified design similar to a popular suppressor designed by Advanced Armament Corp. Yes, that’s the same company that developed the suppressor-friendly .300 AAC Blackout cartridge for U.S special operations.
So the short-n’-sweet of this project is that you can buy a solvent trap for your rifle or pistol for much less than the cost of a typical Gemtech, SilencerCo, or AAC and perform some machining work to make your suppressor relatively easily, and with good performance and cost. You’ve questions, so it’s FAQ time.
Are solvent traps legal?
Yes. Solvent traps are 100% legal to own. The ATF has labelled solvent traps “firearm accessories.” That means it is not a controlled item under any federal gun law, and owning one doesn’t mean you need to file any ATF paperwork. Solvent traps, unmodified, are not considered NFA items like a suppressor.
Do I need an FFL or paperwork to buy a solvent trap?
No. Since the ATF has classified solvent traps as accessories, purchasing a kit is no different than buying any other commercial product online. The kit can be shipped directly to your home of record, and no FFL or other paperwork is required. We do not, however, recommend ever buying a solvent trap that has any cups or cones drilled. These parts could be considered suppressors on their own.
Do I need paperwork to build my suppressor?
Yes. Building a suppressor is like building a firearm at home. It’s legal under the Gun Control Act of 1968. However, a suppressor is also an NFA (National Firearms Act) item. That means you need to fill out paperwork for a background check with the ATF before you drill and cut anything.
The paperwork is called Form 1: Application to Make and Register a Firearm. Along with this paperwork, you’ll need to submit a set of fingerprints on the FBI’s FD-258 fingerprint cards, along with a 2″ x 2″ passport-type photograph. We’ll be linking to a guide that shows you how to do all this digitally. Here are instructions on how to file Form 1.
How much does a solvent trap cost?
That depends on the caliber, physical size of the tube and storage cups, what types of cups come with the kit, and materials used (steel, aluminum, or titanium). Most “turn-key” solvent traps that include all the parts you need cost between $250 and $500. You can buy solvent traps that include only a tube and end caps with no cups or spacers. These usually cost between $130 and $250. You’ll also need to have your tube engraved with its serial number, the name and location of the manufacturer (that’s you), and the model name (if you created one), which typically costs $30 to $60. The tube and caps aren’t considered NFA items, so any machinist or fabricator can do the engraving.
Where can I buy a decent kit?
Solvent trap kits aren’t regulated as firearms, so any retailer can sell them. It’s important to shop for a kit that won’t explode the first time you pull the trigger. Plenty of suspect kits exist on eBay, and plenty more are probably dangerous to use. Stay away from overseas sellers and places like Alibaba or Wish.com unless you want the ATF or customs knocking at your door. It has happened.
A few online manufacturers, comprising mostly small U.S. operations and enthusiasts’ machine shops, produce solvent traps and parts that come with favorable reviews from builders:
- Form 1 Builder
- Quiet Bore
- Solvent Traps Direct
- Medlining Machine Works
- Muted Machine Works
- SD Tactical Arms
- Hawk Innovative Tech
- Silencer Shop
- JR Machine Products
- Solvent Trap Cups
- Apogee Products
- A & L Machine
- Quell Technologies
- Solvent Trap Parts and More
What are some popular setups?
Many builders who favor “abusing” their suppressor builds or firing big-bore or magnum calibers tend to stick to stainless steel and titanium tubes and internals. Many applaud titanium for its ability to handle intermediate cartridges like 5.56 NATO, 300 Blackout, and .308 Winchester while providing a lightweight build. Stainless works best for those big-bore rifles and magnum rounds.
Can I safely use aluminum for my build?
You can, but it’s generally only recommended for rimfire (.22-LR) and pistol rounds. Many builders say aluminum baffles work well with low-velocity rifle cartridges such as subsonic 300 BLK, too. Gunpowder and carbon fouling will still eat away at aluminum and can cause pitting and tarnish, so cleaning should be performed if you build your silencer with aluminum baffles or an aluminum tube.
Where can I get more information on build specifications, baffles, or machining?
Silencer Forum’s Silencersmithing Section provides dozens of resources, images, examples of completed builds, and information relating to sizing and spacing internals, compatibility, and cutting and drilling your cups or cones. The Form 1 Suppressor Builders Facebook group has plenty of resources in the “Files” section to point new builders in the right direction for manufacturers and parts. This is a private group, and you will need to submit a request to join it. The Form 1 Suppressor Boards is a private forum that also provides a myriad of information.