Given the increasing popularity and consistently declining costs of rimfire suppressors, there’s probably no good reason to make your own. Some of us, however, are far too stubborn to let a little common sense get in the way of a good project.
Making a suppressor in the United States is legal, but strictly regulated under the National Firearms Act of 1934. This law also regulates purchasing suppressors, as well as making and purchasing other firearms such as short barreled shotguns, short barreled rifles, and machine guns. In order to legally manufacture what the US considers a “silencer”, it is absolutely imperative that you fill out an ATF Form 1. This requires either filing as an entity such as a trust or LLC, or filing it as an individual and submitting fingerprints and local law enforcement endorsement. It also requires a fee of $200 and, of course, a wait time that’s usually measured in months. Failing to go through this process and get the required permission can result in very serious federal jail time, so play it smart and do it right!
In my case, 126 days was how long I had to wait for permission from the ATF. Once the wait time is up, the Form 1 is received back as “approved” and affixed to it is an NFA Tax Stamp, which allows me to, in this case, manufacture this single suppressor I outlined in my form. The design elements of this suppressor need to be taken under consideration even at the time you are filling out the Form 1; you will be required to submit a caliber and overall length for the silencer you’re making, as well as a model name and serial number. The biggest consideration for this, in an abridged and condensed understanding, is that your stated overall length is basically the longest you may make it, but you can make a shorter can. I’m not a lawyer.
Once my form was submitted and my limiting factors established, there was plenty of time to come up with a design and research materials. This will be important in assuring the safety and effectiveness of the silencer, which are the number 2 and number 3 items of importance after legality, in my opinion.
There are a number of ways to manufacture a silencer. With the market for NFA items opening up wider than it ever has been before, you can even find kits and materials for those who want to do it themselves, but only have limited tools. These range from adaptors for oil filters, conversion kits for flashlights, and other manifestations of pre-existing materials that can be legally manufactured into a functional suppressor using relatively basic tools. I have no idea how well these work; I did not choose to go this route. Anecdotally, however, I have heard many people are happy with the silencers they’ve made out of these various kits.
This silencer will be manufactured out of solid 17-4ph stainless steel and 7075 Aluminum on my small bench top metal lathe. I spent a couple months researching materials, mostly going off of what commercial suppressor manufacturers used as well as other individual silencer smiths. My concern for materials was not only the durability of the material to withstand all sorts of destructive forces, but also it’s machinability. My lathe is usable but of rather small stature, so trying to take complex cuts in a hard material like inconel could prove frustrating.
Machinability of metal is a comparative analysis of how easily a metal cuts and how smooth of a finish can be reasonably attained by cutting. Some metals, like copper and lead, are so soft that they can “gum up” under the cutting tool, possibly leaving a rough and inaccurate finish. Other materials, like inconel and hardened steels, can be too hard, creating heat and eroding the tool, and can have cut finishes that look more “grooved” than smooth, leading to more time, effort, and cost, to get the part machined to satisfaction. Further still, some materials are relatively soft but will “work harden” and become brittle at the surface when cutting is applied; we see this in brass (specifically cartridge casings), some of the more common stainless steels, and titanium. A “machinable” metal is one that is reasonably easy to cut and attain a satisfactory surface finish under reasonably and appropriately paced processes.
17-4ph stainless is the sort of steel used by a number of commercial suppressor manufacturers in silencers from .22lr up to the big bore .30 and .50 rifle cans. It has a remarkable level of abrasion resistance, can be hardened, and also machines very nice as far as a stainless steel goes. To test and prove that my little lathe was up to the task, I ordered some stock and made a variety of test cuts, including outside turning, taper turning, and boring cuts, and was delighted that it does in fact machine very nicely.
7075 aluminum was my next choice for other parts of the suppressor. I wanted to incorporate aluminum to save weight, and 7075 is high strength and commonly used in AR15 receivers.
My choices for these metals were to most reasonably balance strength and weight. The thread mount, blast chamber spacer, and first two baffles I designed to be made out of 17-4. The rest of the baffles and the forward end cap, 7075. The outer tube will end up just being 6061 aluminum because that’s the only aluminum material I could find that met my dimensions, it’s no worry.
Construction of the can is pretty straightforward. The tube will be threaded internally to accept the two end caps, and the baffles will stack between them. The mounting end cap, which I will refer to as the thread mount, will be made out of 17-4ph stainless and threaded 1/2″-28 so that it is compatible with the most common .22 caliber barrel threading. It will, in total, be about an inch long, half of which will be external and the other half threaded into the tube. The external half will have some knurling, which I am planning on doing with a tap, in what I refer to as a “helical knurl”.
The 8 baffles will nest into each other, having a 60 degree cone, and the base of each one will have a matching internal chamfer of 60 degrees. These angles will help the baffles lock together as well as align themselves. In front of the baffle nearest the “entrance”, I will have a stainless standoff spacer to keep the nose of the cone set back just a small amount and allow the gasses to expand in the forward chamber.
The “exit” end cap will also have a 60 degree angle machined onto the internal face, to give a starter reference that the baffles will align off of. With this consideration for alignment to prevent baffle strikes and inaccuracy, I also am keeping the bore of the suppressor at a quarter of an inch, or .250″. This slight overbore will grant a safe amount of distance between the baffles and the projectile to further prevent any contact.
So with these legal, safety, material, and design elements considered, I can move towards taking the first cuts on this can! I’ll machine the end caps first, then the tube. Once the tube is machined, I’ll bead blast it, get it laser engraved with all the required legal information, and then I’ll apply a coating to it. Lastly, I’ll machine the baffles and install them. Once that’s done, I’ll have a fully functional .22 silencer, and the only thing left to do will be to shoot it!
I’m making corresponding videos for this entire operation at my YouTube channel, Practical Renaissance. Here’s the first one!