Building an integrally suppressed 22 barrel

[John1992]

What all options should i consider on building an integrally suppressed 22 barrel? The only technique I have seen is porting the barrel and fitting a sleeve over it and it shot good and sounded good at first but now my buddy that did this is getting terribly inconsistent accuracy.. So I was hoping to get some ideas on a better method if there is one

[whiterussian1974]

Which porting method did he use? EDM or drilling?
If drill, did he fill the bore with anything to prevent burs before drilling?
Has he used a borescope to visually inspect for flaws or defects?

[John1992]

He drilled them.. And Im not certain if he filled the barrel or inspected it but I do know the gun was a tac driver at 40 yards. I could shoot a.25" group almost guaranteed anytime I shot it.. And then about two weeks ago he took the sleeve off of the barrel and the steel wool came out of it and ever since it is shooting all over the place. He has tried putting various amounts of wool back in it he has tried it with no wool but to no ends. Give me one second and I will post a picture of a piece of cardboard we were shooting yesterday trying to adjust the scope and get the gun to group

[John1992]

I can't figure out how to post the picture but anyway its about a 4' tall piece of cardboard and it looks like I shot it with a 12 gauge

[Capt. Link.]

I've built a number of integral suppressors and seen many variants over the years. Some designs are much better than others. Porting for speed control should follow H&K's MP-5SD type porting so minimal bullet deformation occurs. I prefer drilling the ports and use coaxial shells instead of "mesh" type materials as they don't need re-packing. Putting the barrel under tension increases accuracy and saves weight. 1 MOA or better is normal.

Other than checking the barrel for damage, like muzzle erosion you might see if the internal support of the barrel has been compromised or a baffle strike is occurring post re-assembly. The presence of thermal packing should not make a difference on accuracy. How did he clean the barrel after removing the packing....did he use a stainless brush or possibly push burrs into the barrel from cleaning the ports?

Burrs from porting can often be removed with a brass brush. Serious burrs can be removed using a sharp reamer on the ports. Craytex rods or other de-burring like lead laps can also be used.

ps: Steel wool is awful to use. Copper mesh turned into strands and then packed under pressure works much better.
EDM is not needed if ports are drilled and reamed using a sharp reamer.

-CL

[ninoslavt]

and use coaxial shells instead of "mesh" type materials as they don't need re-packing.

Can you post a picture of these coaxial shells, please?

[whiterussian1974]

and use coaxial shells instead of "mesh" type materials as they don't need re-packing.

Can you post a picture of these coaxial shells, please?

I think that he means perforated "spacers" that are nested so that the gas passes through each "shell" sequentially, then must reverse direction and pass through each set of spacers again.

I'd also like to see pics of them. I bet that they are AMAZING!!!

[a_canadian]

About 6 years ago while playing with an old pistol I tried various damping devices around 7 ports in the 7.5" long barrel. Mesh wrap was okay, but quickly got filthy. This was the most satisfying device I used and it lived on the barrel for some months before I decided the whole thing was just way too long at over 16" OAL assembled with the pistol and chopped the barrel down to 4", threading it for more normally proportioned cans.



It's a stainless tube with 0.028" wall if memory serves and about 150x 1/16" holes drilled in it. The holes were located at least 1/4" away from the ports in the barrel so gas had to hit the tube wall then move laterally to escape. Was fairly quiet, but when I later went from the 11" long x 1" OD tube to an 8" long version and dumped the stainless sleeve, noise was only trivially greater, metering about a 1.5dB difference the odd time but mostly less than 1dB. Wear on the inside of the tube was non-existent but it did get dirty and was hard to clean. The advantage of the stainless tube seems mostly to be in tube maintenance and disassembly ease, and for these reasons if I'd kept using the full length barrel I would have gone back to the stainless tube.

This was not putting the barrel under tension as the Captain states for his recommendation, as the barrel of the pistol had a stepped muzzle area (for the original large brake which was damaged by previous owners) which was too small for threading. The bronze muzzle spacer with O-ring was held in place with a grub screw, the stainless steel tube held in thin slots in front and rear spacers about halfway between barrel OD and tube ID.

[whiterussian1974]

canadian, thank you for the photo and description.

Excellent craftsmanship.

From your experience, was the perforated sleeve worth the effort? Would spreading Lithium soap along the barrel have worked better? Cooling both the gases and the barrel as it liquefies?

It seems like the main point of a "mesh" or perf sleeve is to prevent FRP. Was that your finding also?

Might a Metallic Foam doughnut work better? Or would it clog too quickly using dirty .22 powder? How about on a .300BLK or .308Win?

[a_canadian]

No foam, whatever that is. It's just way too filthy, even before adding a bit of white lithium grease. With that stuff it becomes extra-gross in no time.

I didn't think of the porting or sleeve or wrap in terms of FRP. From quite early on in my tinkering with this stuff I learned from folks around here about small blast chambers for .22lr and Dater holes. Having a muzzle to first baffle gap of between 1/8" and 1/4" generally eliminates FRP in my experience, or at least reduces it to such a small difference as to not be worth worrying about. The Dater hole helps a bit further, releasing pressure from that small volume but slowly. I use a thick film of lithium on the first 3 baffles as a habit, thickest on the first. Seems to be about right for keeping the first magazine quieter and making cleaning a bit less difficult, if uglier on the cloth.

The most recent barrel porting I've done is on a 9mm carbine. Shortened the barrel, drilled 8 x 1/8" holes at 45 degrees towards the muzzle to minimize jacket damage and was able to clean up the inside edges of the holes nicely with a flared tip on a diamond Dremel bit. The barrel nut sleeve goes over those ports but is perforated so it doesn't really interfere much, wouldn't count it as having much of a role. So hot gas/smoke/powder is flying back towards the receiver pretty hard in the 4.5" to 5.5" range ahead of the chamber. So far, in a few hundred rounds fired, that has resulted in some surface staining on the 1.375" ID of the integral can's tube. Nothing with texture, just scorching.

In a second build I inserted a 1.375" OD 6061 tube with 0.50" wall, both as insurance against longer term wear from this fiery jetting, and potentially as a further damping element for noise. A minor change in baffle design made for zero measurable difference in suppression. In the first I used shallow pressed stainless steel washer cones with pairs of filed clips, separated by 6061 spacers progressively shorter towards the endcap. In the second, with the thickened OTB section wall, I used stainless steel ATV skid plate washers with pressed 'clips' preserving full steel thickness. No difference at all.

Seems I've topped out what's possible on this semi-auto. Metering noise at the same distance from the ejection port gives an identical result to metering the muzzle noise. Both are quiet enough to shoot comfortably indoors without earpro, for a guy who is very fussy about loud noises. So not a lot of point taking the time to make a set of big K baffles it seems, which I'd rather suspected for a centre fire semi-auto. If I ever cook up some means of locking the bolt on this thing I'll probably make some 'proper' baffles as a better design would no doubt prove quieter in what would effectively be a bolt action 9mm.

So would I use such a filter tube over barrel ports? Seems not. From my experience with several ported barrels in airguns, .22lr, and now 9mm, I'd say media around the barrel is only relevant if that is to be the primary suppression device. Primitive suppressors such as those on sub machine guns in WWII used dense wraps of metal mesh or spirals of thin steel or other ingenious elements to control expanding gases coming from barrel ports because that's about the best they had back then. Baffles were relatively rare, on things like the DeLisle or the Welrod, and tended to be fouled or destroyed after not very many shots - hardly suitable for a high rate of fire application like a Sten. Certainly barrel porting with a wrap of some sort reduced the noise. But pretending it brought that noise down to hearing safe levels, never mind 'mouse fart quiet' levels, is just sentimental nonsense. The real noise suppression happens out front with some form of baffle stack. And anything wrapped around the barrel makes for one more thing to clean. If you need to wrap your ports to prevent jetting damage to the external tube, maybe it's time to look at a lower power cartridge and a weaker return spring behind your bolt, rather than forcing hot ammo through something it'll burn up. I have no idea about .308" etc, no experience and no desire to obtain that experience. I like quiet shooting.