1st suppressor build.. Advise on tolerances. .22lr pistol

[Chipmunk Predator]

Hello. I am expecting my Form 1 stamp to be arriving within next few weeks (fingers crossed). Whie I own 2 other suppressors (9mm & .45ACP) this is my 1st time building one. This will be on a Ruger Mk IV 22/45 Lite and possibly a M&P 15-22 if the barrel threads are concentric enough.

My plan is a 8" overall length suppressor with a OD of 1.230. The outer tube is 6061 aluminum with a .90 wall (may switch to 603SS or TI). Never machined TI so not sure there. The baffles are K baffles with a plunge bore that i will machine on the lathe and mill and i am using 603SS for them and the end caps.

Here is my question. How tight can the bore in the baffles and end cap be? I have seen many say down to .237 and up to .270. I am fairly confident in my skills in machining with tight tolerances and making sure all is concentric with the barrel. What i don't know is how much variation there is in the bullet when it exits the barrel and hits the chambers.

I have drill rod in just about every size from work that i can use to check clearance. I most likely have to order a reamer so i want to make it as tight as safely possible since it will make the suppressor function that much better.

Thanks for your time and advise

[ECCO Machine]

.265" is about your minimum. Any tighter than .040" diametral clearance has a tendency to disrupt bullet flight. I run mine at .275"

1.23 x 8" is huge for a .22 LR can, .090" wall is way thicker than needed. My 124 dB Phoenix IX 9mm can is 1.25 x 8" with .035" wall Ti. 1 x 6" is plenty for .22 LR, if you're threading yourself, go ~.040" wall and use 32 or 36 pitch threads. I use .036" wall on the Ocelot with steel mount & blast baffle, then 9 anodized 7075-T651 cones and a 7075 front cap. 5.5", 4.1 oz, metered 115.43 dB on a 16" rifle with AE 45 gr. subs using the B&K Pulse and shooting indoors.

[garredondojr]

I'm a rookie myself but I want to say most people run .250-.280" I've also seen some do small to large on the apertures (closer to the muzzle tighter and larger towards the endcap.

.090 is way overkill on thickness as is 1.230" OD most people run 1" OD 5-6" long for rimfire suppressors. with .070" being the thickest used and some as thin as .028" If your confident in your machining skills I see no reason to run more than .035-.045" with 36-32tpi
If you thinned the OD of your tube down to a .040 wall that would bring your OD down to 1.13 which would be alot more reasonable.

Keep your blast chamber as small as possible to mitigate FRP

I don't know much about 603ss but don't overlook 17-4ph for the baffles/endcaps. you could even run aluminum endcaps to shave off some weight but I would put a 17-4 insert in for the threads.

I'm sure the vets will chime in soon enough with far greater advice....Nevermind they beat me to it.

[Chipmunk Predator]

.265" is about your minimum. Any tighter than .040" diametral clearance has a tendency to disrupt bullet flight. I run mine at .275"

1.23 x 8" is huge for a .22 LR can, .090" wall is way thicker than needed. My 124 dB Phoenix IX 9mm can is 1.25 x 8" with .035" wall Ti. 1 x 6" is plenty for .22 LR, if you're threading yourself, go ~.040" wall and use 32 or 36 pitch threads. I use .036" wall on the Ocelot with steel mount & blast baffle, then 9 anodized 7075-T651 cones and a 7075 front cap. 5.5", 4.1 oz, metered 115.43 dB on a 16" rifle with AE 45 gr. subs using the B&K Pulse and shooting indoors.

I wanted to use aluminum baffles for weight but read they do not last. That is why i planned on the 603SS baffles and caps. Yes i will be doing all the machining myself. If i had a CNC mill i would be doing a monocore but i just cant afford one at the moment. Does the anodizing help the baffles last on a .22LR. My length is pretty much set since i filled in 8" on my form 1. The rest is still not set in stone. I am looking to make this as quiet as i can possibly make so i can shoot in back yard and draw no attention.

What i needed was the .040 diametral is what i wanted. Did not know when flight would be effected and cause a possible strike. Wish it was tighter but i cant defy laws of physics.

[Chipmunk Predator]

I'm a rookie myself but I want to say most people run .250-.280" I've also seen some do small to large on the apertures (closer to the muzzle tighter and larger towards the endcap.

.090 is way overkill on thickness as is 1.230" OD most people run 1" OD 5-6" long for rimfire suppressors. with .070" being the thickest used and some as thin as .028" If your confident in your machining skills I see no reason to run more than .035-.045" with 36-32tpi
If you thinned the OD of your tube down to a .040 wall that would bring your OD down to 1.13 which would be alot more reasonable.

Keep your blast chamber as small as possible to mitigate FRP

I don't know much about 603ss but don't overlook 17-4ph for the baffles/endcaps. you could even run aluminum endcaps to shave off some weight but I would put a 17-4 insert in for the threads.

I'm sure the vets will chime in soon enough with far greater advice....Nevermind they beat me to it.

YA, i may thin out the outer tube just to shave some weight.
I was planning a 1" blast chamber. Is that ok? should i shrink or enlarge that?
603SS is the same a 17-4PH. The mill i work at makes it so i kind of have an unlimited supply.

[garredondojr]

YA, i may thin out the outer tube just to shave some weight.
I was planning a 1" blast chamber. Is that ok? should i shrink or enlarge that?
603SS is the same a 17-4PH. The mill i work at makes it so i kind of have an unlimited supply.

630SS maybe? if you have an unlimited supply you can kick me some I'll gladly pay shipping.

From what I gather you want the end of the muzzle not too far from the blast baffle so 1" sounds a bit excessive unless thats from the rear of the cap which then would sound about right. big BC's=lots of FRP for rimfire cans.

I think the main detractor from aluminum baffles is cleaning. rimfire can's gunk up quickly and many people like to use "the dip" to clean their baffles.

Anodizing will help with corrosion/and erosion (and i'd assume aid in cleaning??)

I'd venture to guess that raw aluminum would likely last a good while but use 17-4 on the blast baffle. 2024 and 7075 would both make good baffles. My brother works for a aluminum company and mentioned the 7075-T651 and some others that are somewhat classified that are approaching steel levels of strength. same alloy just different heat treatments.

[Chipmunk Predator]

YA, i may thin out the outer tube just to shave some weight.
I was planning a 1" blast chamber. Is that ok? should i shrink or enlarge that?
603SS is the same a 17-4PH. The mill i work at makes it so i kind of have an unlimited supply.

630SS maybe? if you have an unlimited supply you can kick me some I'll gladly pay shipping.

From what I gather you want the end of the muzzle not too far from the blast baffle so 1" sounds a bit excessive unless thats from the rear of the cap which then would sound about right. big BC's=lots of FRP for rimfire cans.

I think the main detractor from aluminum baffles is cleaning. rimfire can's gunk up quickly and many people like to use "the dip" to clean their baffles.

Anodizing will help with corrosion/and erosion (and i'd assume aid in cleaning??)

I'd venture to guess that raw aluminum would likely last a good while but use 17-4 on the blast baffle. 2024 and 7075 would both make good baffles. My brother works for a aluminum company and mentioned the 7075-T651 and some others that are somewhat classified that are approaching steel levels of strength. same alloy just different heat treatments.

Not sure if this matters. I had planned on making a .750 spacer with a schrader valve to purge suppressor with nitrogen. Hoping that kills the FRP. Then have the 1" BC before the baffles. I can reduce this size to whatever. If i make it small enough i can add an extra baffle. I have to purchase my aluminum so i only wanna use it to cut weight. If its negligible then i will use the 603 (17-4).

[Capt. Link.]

On building ...
I would keep the blast chamber to under 1/4" and plan on using a Dater hole to help with FRP.Copy a high performance K baffle as they are better than most of us can design (AAC). You will need to use something harder than aluminum for that first baffle or two simply to reduce cutting from the abrasive used in the priming compound.7075 is very good material for the rest of the stack when anodized but SS is better as it needs no finish and won't corrode.You should be able to fit quite a few baffles in a eight inch can so it should be quiet if built well. You can bore baffles any size you wish but +.060 is more or less a standard for asymmetric baffles like the K type, I reduce that to .040 on cone and other symmetrical baffles. This works provided that you have very low runout.
Ask and you shall receive.
-CL

[fishman]

Copy a high performance K baffle as they are better than most of us can design

hey now. Play nice. Lol

[Hard_ware]

Looks like you got it sorted out.
I think you can go shorter on your form1 but cannot go longer without making a change with ATF.

I am building a 1” for 22lr with aluminium tube, 17-4 baffles just thinning them out after first blast baffle to cut down weight.

Edit. Looks like aluminium baffles anodized will be better.

[ECCO Machine]

Double

[ECCO Machine]

I wanted to use aluminum baffles for weight but read they do not last. That is why i planned on the 603SS baffles and caps.

In pistol and rimfire cans they do. Stainless is certainly tougher, but there's a substantial weight penalty in cans where very thin Al baffles are sufficient.

Heat is what kills Al, which is why they aren't found in centerfire rifle cans aside from ultralight hunting types.

If i had a CNC mill i would be doing a monocore but i just cant afford one at the moment.

Monocores suck. Some manufacturers like to pop them out because they're faster to make and more material efficient, but they will never perform like stacked baffles. Can work OK on .22 LR, but if you want to use the can for .22 WMR and the like, definitely stick to cones.

Does the anodizing help the baffles last on a .22LR.

Yes, makes the surface almost as hard as treated tool steels. The substrate is still soft, but it will help with the sand blasting effect of unburned powder granules and other debris at high velocity. Also makes cleaning easier and prevents galvanic corrosion (the anodic layer is dielectric)

My length is pretty much set since i filled in 8" on my form 1. The rest is still not set in stone.

Make it modular then; something like a 4" base can with a couple of 2" add-on sections.

What i needed was the .040 diametral is what i wanted. Did not know when flight would be effected and cause a possible strike. Wish it was tighter but i cant defy laws of physics.

Going tighter wouldn't make it any quieter anyway.

[John A.]

The advice already given is top notch.

.90 wall outside tube is 2x thicker than it has to be, but .058 gives more than enough room to thread and whatever else you need to do. As for inner spacers, .038-.045 wall would be alright. Maybe even a little thinner. You're just holding back a little puff of smoke and gas

The one that I have in the pipe, I plan on using 1.120" OD and the ID is going to be around .97ish.

Aluminum baffles are more than adequate on a 22 rimfire. Unless you plan on running it full auto, which I don't expect you'll be doing on a Ruger Mk 4.

On a rimfire, the G core monocore baffle works well. But as ecco mentioned, less than ideal on other calibers. Rimfire is pretty forgiving to make a decent can for.

K baffles and the G core are probably among the most quiet rimfire baffles currently out there.

Oh, I'm going around a .28" (9/32) bore. Maybe a 7mm bore (.2750)

[Capt. Link.]

I have no issue with using aluminum baffles .22Rf through .45acp if they are hard anodized . Its very difficult or expensive for the form one builder to get aluminum type 3 anodized. Its a commercial process that must carry a FFL $$$$. The home processes do not add any hardness to the surface but will protect the baffles from corrosion.It all comes down to longevity and monies spent in maintenance of the suppressor.Titanium and SS need no special treatments while carbon steel and aluminum do. I think there is a savings in labor and longer life if you use SS or other alloy.
The other issue is using baffle that is normally spaced close to the muzzle of a .22 pistol or rifle.The erosive effects of volcanic glass priming compound is a obvious threat to the longevity of that first baffle.Long ago diffusers kept the spacing fairly distant from the blast baffles of the day and aluminum worked well. Ever since the invention of the K baffle and close spacing now common, harder materials are more economical in my opinion for .22 rimfire cans.
-CL

[ECCO Machine]

I have no issue with using aluminum baffles .22Rf through .45acp if they are hard anodized . Its very difficult or expensive for the form one builder to get aluminum type 3 anodized. Its a commercial process that must carry a FFL $$$$. The home processes do not add any hardness to the surface but will protect the baffles from corrosion.
-CL

Type II anodizing absolutely does create a hard anodic layer. It's (typically) thinner than type III per specifications, though it can be just as thick. Another aspect is that type II spec calls for sealing, which inproves corrosion resistance. Type III can be sealed, but it's not part of the spec and it usually isn't. Type III being denser (smaller cells) and generally thicker does make it more wear resistant, but a good type II certainly resists wear orders of magnitude better than natural.

If you type II anodize at lower temperatures and pushing higher voltage and amperage with more cathode, you get a (somewhat) dyable anodize that's pretty dang tough. I shoot for a 50° bath, use a higher cathode ratio, run 22-24 volts and pour in the amps. I have 3 separate power supplies with variable voltage and different amperage outputs, might use one, two or all 3, depending on how much surface area I'm anodizing.

I have found this (type 2.5, shall we call it) doesn't take lighter dye colors well, so behaves more like type III in that capacity. Black comes out good, though.\

Titanium is another story, and home anodizing really is just cosmetic, although I've found a fine bead blast and anodizing in the same sulfuric acid bath with lead cathode plates that I use for Al does improve scratch resistance.

[fishman]

Titanium is another story, and home anodizing really is just cosmetic,

it will allegedly reduce the chance of galling threads

[Hard_ware]

When anodizing aluminium going from type 2-2.5 could the dye be added at type 2 before continuing to type 2.5, or does the lower temps and reduced acid concentration start the smaller cell formations of of type 3,( which is hard to dye) when you start the process.

Just thinking a pulsed current source can control the amount of energy added to the solution which will control the temperature. So a temp controlled pulsed system can be setup to only allow enough current to keep the temps between 30-40 degrees if a ice bath is used to surround the anodizing container. Process will take longer but temperatures could be controlled this way.

[ECCO Machine]

it will allegedly reduce the chance of galling threads

Sulfuric acid bath type III anodizing of Ti does seem to make the surface a little tougher. I'm sure there are other bath types that will do the same, but that's what I use, since I have no shortage of H2SO4 around here. Like I mentioned, my bead blasted and anodized tubes are decidedly more abrasion resistant than natural finish, but it's not type II tough. I do it at 16-17 volts for about 10 minutes, which produces a purplish color that turns a wonderful matte grey when rubbed with oil or silicone, and pretty well stays that way unless you degrease it.



It was more dumb luck than research on my part which led me to realize what sufuric acid anodizing can do for Ti. I quickly tired of cleaning or replacing aluminum anode wire every single time, and the Al didn't hang onto parts as well either. I started using CP Ti wire and discovered that the submerged portion had a noticeably harder surface, wire that had been used was less malleable and more abrasive to the Al part than new wire.

When anodizing aluminium going from type 2-2.5 could the dye be added at type 2 before continuing to type 2.5, or does the lower temps and reduced acid concentration start the smaller cell formations of of type 3,( which is hard to dye) when you start the process.

Just thinking a pulsed current source can control the amount of energy added to the solution which will control the temperature. So a temp controlled pulsed system can be setup to only allow enough current to keep the temps between 30-40 degrees if a ice bath is used to surround the anodizing container. Process will take longer but temperatures could be controlled this way.

No, if you try to take a part out and dye it, then stick it back in the acid bath, you'll just bleed the dye out as the oxide layer penetrates deeper.

It takes the black pretty well, so it works for me.





Type 2.5 is not an official designation by any means, just what I'm calling this process that doesn't meet spec for type III but is done at higher voltage & amperage than typical type II and producing an anodic layer that it more difficult to dye. When I want to dye other colors, I lower the voltage & amperage, pull the cathode plates further out of the bath. There is a noticeable difference in the abrasion resistance of a part I do at 12-14 volts which takes reds, blues or other bright dye colors well and the ones I do at higher voltage which end up faint and splotchy with those colors.

I'm not an anodizing expert, and really don't have much experience anodizing Al alloys other than 7075-T6. I've figured out how to get good results with that, though.

[Hard_ware]

Thanks!

[Chipmunk Predator]

I thank all of you that have replied with information and advise. Thinking i need to reevaluate my design and sizes. Not 100% sure if i will be able to make it shorter that i put on my form 1. I am going to switch my baffles to the 17-4 (603SS). I really wanna try Ti but i have never machined it before and its not real cheap. 12" of 6AL-4V is around $200. Guess my 1st step is to find out if i can make it shorter than my form 1 application. Thanks again!!

[John A.]

Not sure if this matters. I had planned on making a .750 spacer with a schrader valve to purge suppressor with nitrogen. Hoping that kills the FRP. Then have the 1" BC before the baffles. I can reduce this size to whatever. If i make it small enough i can add an extra baffle. I have to purchase my aluminum so i only wanna use it to cut weight. If its negligible then i will use the 603 (17-4).

I just noticed this.

I admire the desire to do something different, but wouldn't it be so much easier, cheaper and less annoying just to make a small expansion chamber so you wouldn't need to charge it with nitrogen in the first place?

1/2" expansion chamber should work fine for 22 rimfire with little to no FRP.

Also, an Al baffle will last a very long time in a 22 unless you just abuse the crap out of it with dump after dump for a couple of years every time you take it out. If you worry about erosion, make the first couple of baffles a little "thicker" to give them a little extra meat on them. Of course, a stainless baffle will probably outlast most all of us here LOL

I've been using a thin coating of anti-spatter weld gel before shooting rimfire through my stuff lately and it seems to help keep some of the buildup from forming. The gel seems to make it a little more quiet, kind of like ablative FWIW, I clean my stuff pretty regularly. I don't pretend to know how long the gel will work, but I've not noticed any bad problems from using it on my 9mm baffles while shooting 22 through them.