Originally Posted By shooter64738:
Hey all. With the tax becoming $0 I've been wanting to put this out there, maybe save some people trouble, experimentation, and testing money.
I'm going to skip the background story, but here is what I have picked up in the last 15 years working with 3d printed suppressors

Most of my testing has been on rifles, and a few pistols or pistol carbines. When I refer to accuracy, I mean that the shot to shot drift must be as good or better with the suppressor than it is without the suppressor.

NONE of the polymer printed suppressors will hold up to a point of a stainless, titanium, aluminum, carbon steel, etc suppressor. Its just not going to happen. But you can stay with in the limits of the polymer and get 100,000+ rounds out of a rim fire version, many thousands out of pistol calibers, and a few thousand out of some rifle calibers.

Don't assume larger calibers are harder to suppress than smaller calibers. The trick is to design a suppressor to contain the volume AND the VELOCITY of the gas. If you don't consider both, it will fail prematurely. I can suppress a 308 rifle with a printed suppressor, so long as the barrel is 18" minimum. for 308 is the volume, not the pressure (vent it fast through large ports). For 5.56 its the velocity of the gas (vent it fast through passaged), not the pressure. The gas velocity of even sub sonic rounds, can exceed 3000fps on some calibers. So keep that in mind.

Phase 1: Print it, screw it on and test it.
This is what most people think of with 3d printed suppressors. The pros are that its simple and easy to do, pretty cheap (if you don't count cost of printer) and once the print finishes, you are pretty much done. The cons are, they don't hold up well to external forces, your accuracy is minute of barn door, they soften in the sun or in a trunk. Material choice is important here, because you are relying on the polymer for its layer adhesion, tensile strength for pressure, and its rigidity to stay straight. This will not prevent the suppressor from flexing and causing your shot to shot poa/poi form moving all around. Accuracy is pretty bad.

Phase 2: Print it, use a metal insert and test.
Similar results to phase 1, but we could get more shots out of a single print before it began to deform and droop at the barrel. The same issues exist with gas pressure/velocity because once passed the metal thread insert, its polymer only holding it together.

Everything was stagnant at phase 2 for about 3 years, and then I came up with this...

Phase 3: Print it, do special things, test it.
You will need to rethink the way you would build a suppressor (or anything for that matter). The suppressor is made in pieces consisting of a base (where your thread insert will attach), your tube (everything goes inside), your baffle stack ( the thing that does the suppression), and an end cap. Now consider ALL of these components are printed with a single wall (or sometimes 2 wall) and they are paper thin, and fragile. This is not something you think of when you want to build something robust, but keep reading.

You have 2 options.
Phase 3: option 1 (not very diy friendly, and I'm only giving a very broad description)
You have your pieces printed in ABS. Get formaldehyde, phenol resin power and mix these together with a 5% acetone solution. You will inject this into your hollow (and very fragile parts), put this in a vacuum chamber so that water boils at a lower temperature. (90*c is a good target, but it needs to be below 100*c minimum). As the phenol resin gels up the acetone will be slowly eating the abs away. After 12-14 hours the part is semi rigid and mostly no longer supported by the print. You can increase the temperature to 150, then 200. In  about 30-45 minutes, the resin is set, and you can let it cool. You have now created a suppressor with the shape you printed, and turned it (mostly) into phenolic resin, which you cant melt. This is know by the common name of BakeLite. This took months to get to work, and the fail rate was high. I tired it with acids and bases, and I don't think this is as diy friendly, but its out there...

Phase 3: option2 (diy friendly)
Print your pieces out of I dont care what.. pla, pla+, petg, abs, pa6cf, we don't care... Thin walled hollow prints, very fragile. Get a 1g injection needle and at least 50cc syringes. You will now get standard table top casting epoxy with 7500 tensile strength, and 15,000psi compression strength. You will perform similar steps as above, using a 12g injection needle you will inject this epoxide resin into the hollow parts and let it cure. When its cured (follow direction, usually 24 hours) set your oven (or something at 150*F) let it preheat. Now shut the oven off, and place your parts in there and let it just cool on its own. This should pretty much guarantee that the epoxy resin is 100% cured.

My Phase 3 option2 is easier than option1, and I didn't see much advantage between the 2, except that you can get option 1 hot as hell and it wont melt

Phase 3 option 2 is diy friendly, produces an extremely rigid suppressor which will maintain or improve accuracy on any rimfire rifle. I would demo these at rimfire competitions using a wal-mart savage bvsr 22 rifle and hitting a 4" gong at 250 yards.

But wait there is more... You can buy titanium mesh (there are dental meshes for facial reconstruction, but they are annealed usually) you can roll that mesh up into a tube shape and slide it in between your baffle core and your outer tube before putting the end cap on and injecting. This will make it stronger without adding weight and you can lose some wall thickness to lighten it.

The draw backs to any of these is external shock. the injected versions are much stronger (to the point you could use the suppressor as a club) but if you lean a rifle against a wall and it falls over or my favorite, ratchet strap a rifle to my 4 wheeler and bang it into trees on a trail.. You do run the risk of it snapping off. so again, its not metallic, use it within its limits.

Condensates:
Yes if you have a rimfire can everyone wants to take them apart to clean them. This doesn't exactly hold true for printed suppressors. The polymer stays cold when shot and doesn't hold or transfer heat well at all, so unburned powder and debris don't stick to it and build up as much over time. I cleaned these with 90% alcohol, and rinsed. I've made many of them that can come apart for cleaning, but they don't hold up well.

Thoughts:
My absolute favorite one is the one i demoed my cheap ass savage 22 with. Its got to over 100,000 rounds through it, is a simple cone baffle (I've made every conceivable low pressure design you can think of) and this one was just simple and worked superb.

Recommendations:
So the best option for making one that you could keep for your entire life? Phase 3:Option 2. These are fantastic for any rimfire, pistols up to 40cal, 300 aac, and if you are careful and use titanium mesh, even 308 on an 18" barrel. Build cost is probably around $50 these days. You will need a metal base for your threads. The drawback is, you can rapid fire to a limit, but don't cross it. On a rimfire keep mag dumps <100 rounds. on a 9mm/300aac <45 rounds. If you go beyond that, its probably going to start deforming internally.

Alignment: always that pesky alignment..
Print your tube. Print a huge cone. The cone should have an inner hole that SNUGGLY fits the outside of your barrel, but is not impossible to move. The outside of the cone is about 2" in diameter at its large end. CLEAN YOUR Z SEAM on the cone (or print it into a divot) slide the cone on your barrel, slide your outer tube on your barrel. (the barrel is sticking out the hole in the bottom of the tube where your insert screws in). Screw the insert on your barrel (backwards). Put a small dab of 5 min epoxy on the outer threads of your adapter. now slide the outer tube down to the adapter and screw it on. Slide the tapered cone into the open end of the tube. Let the epoxy set so its well cured (couple hours). Now you can unscrew the tube from the barrel and it should be perfectly concentric with the bore of your rifle. If the adapter was machined flat when it was made, you should have nearly perfect alignment.

Design thoughts:
Any cad model you design should use radiused connections from part to part. A baffle should not just stack onto another baffle in the print. it should connect with a radius. for gas speed up to 1500fps use 2mm radius minimum, 1500-2000 3mm, above 2000 i have used 4-6mm but that's getting into some hard to capture territory and other things need to be considered too. Use a minimum gap of 2mm between your outer tube and baffle stack. 3mm without re-enforcing mesh, but you can go to 2mm with mesh. And no screen wire wont help (been there, tried that). For larger calibers like 308, use perforated stainless tube as your 'mesh'

Conclusion:
After all these years trying to convince people to purchase cheaply made suppressors that would hold up over for thousands of rounds, I give up. Its polymer, therefore it sucks... So this is a broad overview of knowledge and experience I gained. Hopefully its helpful. All the prototypes we built have been cut up and when this money pit of a license expires, I think I'm calling it quits.

Originally Posted By youngandfree:
Have you done any printing with titanium or metal infused filaments and done the debinding and sintering process?

Originally Posted By shooter64738:
I either did 1 wall (.4mm) and then coated the print with wax to prevent leaks, or 2 walls (.8mm) and injected directly.

It mostly came down to the internals. If it was a helix, or some type of spiral/low blowback design for gas venting, 2 walls (.8mm).

I dont recommend just printing anymore because I never could get great accuracy from one. If accuracy is only a generality, then print only, is fine.

For context I tested these on a 10x and a BSA 22 rifle shooting lapua and midas ammo at 100 yards in a sled under really controlled conditions. I wanted to know what you really need to do for accuracy.

The resin injected versions won hands down every time and not by a small margin. I would see a 6" groups shrink down to a 1" group using the same internal designs, and only changing the build method.

When you show up at those rim fire bench rest competitions and you give them anything less than a .5" group, they just laugh at you. They take their craft pretty seriously.

All that said if you want print only, I go with a wall count of 15 or 20 so its entirely solid material, and no less than 3mm from any internal space to the outside edge of the tube.

If you can turn on a lathe, a pistol buffer tube can be cleaned up, and a threaded cap can be bored and threaded. Screw that in the tube, face it off, bore and thread it. Print a classic stacked baffle assembly that fits snug in the tube. It'll last you the rest of your life if you dont mag dump all the time. Your baffles should be 2-2.5mm thick, and I spaced mine 23mm apart.  First baffle should be 15mm from your muzzle for best general subsonic accuracy.