With the mod's approval, I'd like to post pics of my .22LR muzzle can "enroute".  My goal is a suppressor for .22LR only which will be mounted on a 5" Kuehl bbl.  

I am not happy with the appearance of a small .22 muzzle can on an AR due to the midget diameter... it just doesn't look right!  By going from 6" long by 1" dia (typical of a CAC-22 and similar) to a jumbo 1.75" dia X 8" long, I hope to approach the elusive "hollywood quiet", as well as simply have one of correct scale.

I contemplated K baffles and other modern configurations, but decided to initially use older technology.  I am going to make the can modular and upgradeable, so I can improve the can later if I want to.  I am hoping that the huge internals of this can, even with the old technology, will be nice and quiet.

I have gathered up a large assortment of DOM tube.  The can will be carbon steel.  After testing, if it works as I hope, I will park the internals, and possibly moly-cote (or park) the tube itself.

WARNING!  DO NOT MAKE A CAN, NOT EVEN A SINGLE BAFFLE, WITHOUT A BATFE APPROVED FORM 1 IN HAND!!!!!!  DON'T BECOME BUBBA'S B***H BY BREAKING THE LAW!

Mods, if this is inappropriate, delete this thread.

Facing the ends of the tube



The base threads, 3/4 done


More to come!

Look closely at this picture:



You can see on the right baffle a .032" shelf.  The rims of the baffle on the left connect to this shelf and prevent the baffles from rotating relative to each other.

could you please explain how you keep the square baffles from becoming mis aligned? thanks Lee

I'd like to build a silencer for a 10/22 that looks like a full length bull barrel... If the tube is 20" long and fitted over a 8"barrel, does the tube need to be permanetly attached to the barrel and the baffles removable from the front cap only? It seems if the tube was removable from the barrel, I would also need to register the 10/22 as a SBR. Yes the tube would need to be permanently attached if it is not a SBR. Or can I just make sure and keep the tube on the gun until the stock is removed? If your 10/22 is not a SBR then you cannot have the short barrel on it even when the stock is removed as it was never a pistol. Sorry for the noob questions guys... just wanted to make sure of these things before I mailed off the forms. Thanks!!

tag

gorilla

read your post. been there with the "hollywood quiet " can using 22LR subsonics, you can read my post in this forum Reflex-OPS Hybrid, and view pics of my new can thanks to Fiz.

keep us up to date. I have wonted to build one under a form 1 for a long time.

I take it then that this thread is a "go".  I will continue to build and add pictures.

jbj16, I'll look for your stuff.  I know this effort (big, fat .22LR can) isn't novel or new, it's just something I've wanted to do myself for a while.  By being the manufacturer, I can modify and repair the can and remain legal.

It's going to be intentionally heavy.  I chose thicker-walled tubing so as to produce coarser threads, and the baffles will be likewise heavier than a commercial unit.  It might be able to take 5.56 semi, but being mild carbon steel, there's no way it can handle a lot of heat or sustained fire.  The threads in the picture are 24 TPI, a tad coarse but easy to cut.

My Kuehl bbl is threaded 1/2 X 28 right now.  I am strongly leaning towards turning the bbl to create a two-point mount.  BBL OD is 0.875". I'm thinking about cutting a 5/8" X 24 thread section about 2" aft of the muzzle, and turning down or parting off the current 1/2" threaded section.  


The internal thread section has just been relieved at the bottom of the threads.  Note the tool which has just cut the groove at somewhat greater than full thread depth.  This allows the single-point threading tool to come to a halt "in air" after making a threading pass.  It's always a bit exciting threading up to a shoulder!  My lathe has a thread-tool kickout which disengages the carriage at a specific Z location, so I can drive the tool into a narrow groove and have it reliably stop without having to frantically slap at the half-nut, or fiddle with the X axis.

Looks nice.


Add some cam followers to the steady rest !

Swede ?   I recognize the URL on the pics...   This fellas work is awesome if you have seen previous posted work the last yr or so.

I still have not finished looking at the stuff on the homepage, there is some impressive stuff there.

Busted!  Thanks for the kind comments.  I tried to register here at AR15.COM as Swede but the handle was already taken.

The suppressor build continues...

I am more or less making this up as I go along, but I have an internal layout in mind.  I'll see if I can't get a JPG up of my internals.  For now, the external/easy parts are coming along nicely, altho very heavy.  That's OK, it's not a pistol can.

The end cap is turned from 12L14 mild, leaded steel, really easy stuff to turn.  The threads match the tube, and are 1/2" long.  The interior is hollowed out into a semi-rounded chamber.  I intentionally left a lot of meat in the end cap so that I can bore and if necessary change the diameter of the exit hole, which is 0.250" for now.



I parted off the end cap, gave the rim a coin knurl (which can be removed later if I don't like the looks.)  Installed on the tube, the rough parted surface is trued relative to the tube axis.



I also drilled (not thru) a set of holes for a pin wrench.  Still on the tube, the thickness of the end cap is obvious.  For now, I am ignoring the tube finish... everything is focused on the accuracy of the bore and the internals.  The LAST thing I'll do is turn the exterior of the tube concentric with the tube's bore, and give it a nice finish.


The challenging muzzle end is next, then the baffles and the remainder of the internals!

This is a great write up. Please keep the pics coming. I plan to build in the future, and this will help me out greatly.

Mods: Is there a way to get a tack on this post, some great info for us home builders.

Originally Posted By David_Hineline: I have never done a coin knurl, it looks good,  I would think since the Knurl has a specific spacing that if the diam of the material was not just right for the spacing there would be a point on the knurl where the spacing was not quite right? Seeing what real lathes can do makes me covet something other than my chicom combo machine.

David, the knurler doing the honors is a Quick brand knurler.  This style of knurler is different in that the knurling wheel actually cuts the metal rather than forming it with pressure.  Don't ask me how it does it, but it's like magic, and forms knurls with very low pressure.  I understand your question, which applies more to coarser diamond knurls.  With this thing, I simply feed it in until the knurl looks good.  It cuts until I stop the infeed, and it basically (and automatically) creates knurls without skipping or bad spacing.

Quick knurlers are usually >$150... I bought mine used for $10, along with an AXA holder.

I'd like some opinions from you guys.  I can't decide whether to go with a standard 1/2" X 28 single-point mount which is typical of almost all .22LR cans, or turn my Kuehl down and execute a two-point mount.  

Pro's - 2-point mount will be stronger and more accurate for alignment, and allows the creation of a modest blast chamber area behind the muzzle.  May need to cross drill bbl to bleed gasses, something I'm loathe to do.  Shorter OAL of weapon.  

Cons - the mount is now pretty much proprietary to the bbl... suppressor cannot be moved to another gun without extensive mods to the new bbl.  But it's not like I'm going to hang this can on a P22!

Thoughts?  I'm leaning towards 2-point.

I say 2 point for the blast chamber. Looks better with a 2 point with longer barrels. Just my 2 cents.

tag

Gorilla Hi!

How about this project?

Sweet!  Any photos of the internals?  What is the OD of the tube?

Mine will differ a bit in that it will be on a really dinky Kuehl bbl.  The OD of the tube right now is at 1.750", which is the ID of both floating handguards that I have.  By turning the finished can down maybe 0.032", it'll fit inside the handguard.  It'll look a bit like a dedicated & suppressed 9mm upper.  Optics will be required, I'm leaving no method for a front site, altho one might be mountable on the handguard's rail.

Here's my concept for a very simple 2-point mount.  I don't want to make it too big as I simply don't have that much bbl length to spare right now.  The bbl measures 6.5" from breech to muzzle.  I'm thinking 2" or so.


The bbl threads will be .750 X 32.  The muzzle end will be turned smooth to 0.625" OD.  Internal boring of the bbl will be 0.437" X 0.750" long.  This bored area will be cross-drilled to bleed gasses, and the muzzle support washer will also be drilled to allow gasses to flow.  Gunk will build up on the bbl exterior, but it will still be removable with ease as the muzzle end OD is less than the 0.750" threads.

I'm thinking a good way to port the bbl will be to apply the flank of a 3/8" end mill to the side of the bbl.  As it breaks through, it'll leave a sharp edge internally, which will flare out to the blast chamber area.

I haven't turned any more of the suppressor, just spent some time and thought on this area.  Thoughts?

Gorilla,

Regarding the pic, ID of the can is 1.75 in. The barrel sleeve is closed and abutts on an OPS Type collar and is threaded forward 1/2x28TPI.  Overall length of the can is about 280mm and weighs approx./ but not  like a 1911 . Its heavy but it will suppress well and at the same time will tolerate maybe 3-30rd mag dumps. Im not humping it thru the boondocks like the military so weight is of little concern but durability and max. suppression is.

My concern about your 2 point concept is that it will expose the external barrel surface to the heat of the blast dischagre. Heat IN the barrel during firing and trapped heat IN the blast area could do damage I think to your barrel, short of re-heat treating the 4140 steel during firing. Any way that's why I designed my can with the requisite barrel sleeve to protect the exterior of the barrel from the Plasma during firing.

Gorilla,
Curious as to who's threading tool you are using, been looking for one and up until now, I've been using a 60 deg tool bit in a boring bar.

--C

Makes sense.   I was considering a collet type arrangement for 2-point mounting, rather than turning down the bbl, and shielding the bbl exterior from hot gasses.  Both of my Kuehl bbls are a very consistent 0.875" +/-0.001" OD and a collet arrangement for a two-point mount would be feasible.  

But on the other hand I want to keep it simple.  A truly simple can would be a straight 1/2 X 28 single-point mount, but when the can is as massive/heavy as this one, I am not confident that I could avoid a baffle-strike with a 1-pt mounting.  I want to keep the tolerances on the baffle holes small and tight for best efficiency.

I'm going to redraw the rear end again, and look for another method.

Heat:  I've done many back to back mag dumps with my Vector in .22LR, and my impression is that the heat really isn't much of an issue.  Sure it'll warm up but NOTHING like a rifle round.  I am confident that any steel (carbon or stainless) suppressor can handle FA .22LR all day long.  SS is superior for both heat and corrosion resistance. I've seen heavily parkerized suppressor internals though and after mucho .22LR there was no evidence of corrosion, assuming the can is shot dry, no H2O or other water-based coolant added.

That's where I am, trying to balance simplicity with excellent function.  What's cool about a homemade can on a F1 is the ability to repair/rebuild it, improve it, etc.  Experimentation is appropriate.  Along these lines, having the primary tube being well-built and solid, the same tube can have its internals replaced, going from straight/plain baffles, to K-baffles, etc. without running afoul the BATFE, so long as you don't have 100+ baffles kicking around the shop.

Originally Posted By CS223: Gorilla, Curious as to who's threading tool you are using, been looking for one and up until now, I've been using a 60 deg tool bit in a boring bar. --C

It's an ISCAR "miniature" internal threading tool.  Those tiny inserts are good only to about 20TPI, anything coarser and the tooth doesn't have the depth.  But they are super sharp and efficient, and cut very well.  Shank is 5/8" and will fit an AXA holder.

I tried to link the PDF page which shows the tool, but it doesn't work.  Go to MSCDirect and enter this stock number in the search box : 60874120

If you're a typical hobbyist, 5 inserts (3 tips per insert) will last for many years.

have the inside and internals hard chromed..

Originally Posted By Gorilla: Heat:  I've done many back to back mag dumps with my Vector in .22LR, and my impression is that the heat really isn't much of an issue.  Sure it'll warm up but NOTHING like a rifle round.  I am confident that any steel (carbon or stainless) suppressor can handle FA .22LR all day long.  SS is superior for both heat and corrosion resistance. I've seen heavily parkerized suppressor internals though and after mucho .22LR there was no evidence of corrosion, assuming the can is shot dry, no H2O or other water-based coolant added.

One thing I would like to point out for general information is that heat isn't a problem with FA .22LR when using steel construction but leading is. Currently I have a AAC Ranger that a customer purchased with his AM180. Stock weight is 18 oz, I weighed his can and it is 25.3 oz. There is 7.3 oz of lead built up in the can and an ultrasonic cleaner won't phase it. It cannot be disassembled for cleaning. It is imperative to be able to disassemble any .22LR can used in a FA application.

Originally Posted By CS223: Stock weight is 18 oz, I weighed his can and it is 25.3 oz. There is 7.3 oz of lead built up in the can and an ultrasonic cleaner won't phase it.

Holy cow!! That's a pretty significant amount of "build-up". Is that a normal occurance?

The simple .22 Can build continues.  I'll say once more, THIS IS ILLEGAL UNLESS YOU HAVE AN APPROVED BATFE FORM 1.  YOU WILL GO TO JAIL IF CAUGHT WITHOUT THE NECESSARY PAPERWORK!  If you have the tools to make a suppressor like this, then you'll also have the $200 for the F1 tax and the necessary maturity and patience to get it approved.  See the FAQ.  

With the tube interior completed, as well as the end cap, I began to contemplate mounting; 1 vs 2 point, etc.  I'm still leaning towards a very simple two-point mount for a can of this size.  In the meantime, I decided to turn a number of spacers.  These spacers can be used to separate simple washer-type baffles, cone baffles, etc.  I'm probably going to start with simple internals, and if that doesn't perform as I'd like, I can destroy then and try K baffles or something more modern.  One HUGE advantage of a large can is that the sheer internal volume itself will go a long way overcoming the limitations of cruder baffling.

One thing that must be remembered is concentricity - everything relies strongly on the bore of the tube, and the accuracy of the baffles.  Tighter tolerances will allow smaller through holes without risking a baffle strike.  The bore of this tube, which is seamless, is a very nice 1.498 +/- 0.0007 or so.  Unless you have a lot of skill and some rigid equipment, I'd accept the bore that a seamless, cold-drawn tube will deliver, rather than try and improve on the accuracy of the tube, as drawn.



Spacers are best made from DOM tube a size smaller than the outer tube.  Be sure the OD is slightly larger than the ID of the main tube, so that the spacers can be turned down to a nice sliding fit.  In this case, the tube OD is 1.503", allowing me to turn off ~ 0.007".  The use of a dial indicator allows me to center the tube accurately before making this skim cut.



A test cut is made; the OD measured, and tested for fit with a piece of the larger, main tube.  In my case, a spacer OD of 1.496" fit well.

continued...

While everything is concentric, a heavy boring bar removes a bit of stock from the bore of the spacers.  All of my tubing is heavy-walled, and the spacers do not need to be especially thick.

I took the spacer ID to 1.370".  Final boring to a 1.375" ID will occur with the parted off spacer chucked and clocked dead-true.  This means the OD and ID will be absolutely concentric with each other.




I parted off a series of spacers, several of them 3/4" long, fewer at 1" long, and a single 1.5" spacer for the blast end of the can.

Parting DOM tube can create resonances that will cause the tube to squall at decibel levels that feel like they are causing your ears to bleed!  I shoved some wadded-up paper towel in the bore to kill the ringing.

Today I'm going to try to get to work on the mounting end, and perhaps turn a baffle or two.  My plan is to TIG weld the baffles/spacers together at a low amperage, to form a complete unit.

Cool, a sticky!    Thanks!

Right now I am in the process of turning down a virgin Kuehl bbl, which as you can imagine is not real pleasant.  I am also working on a simplified 2-point mount with a modest blast chamber.  My first step will be to turn the bbl down to handle the mounting.  Approx. 2" of bbl will be reduced in diameter.

My question to you guys is porting.  My first inclination is to bore the muzzle of the barrel open a bit, say 0.375" ID, for perhaps 1" deep, then port from the side.  I am hesitant to port directly through the bbl and rifling into the bore, which unless done properly might cause flyers and baffle strikes.  Does this make sense?  Am I being a whimp?  Should I drill holes as the bbl is, then perhaps slug it with some emery paste, to remove the burrs?  I'm sure that porting the bbl directly is superior, I am just not sure of the technique.  Replies appreciated before I trash this barrel.

Guys, please help, I need some opinions... the barrel is sitting in the lathe, Dead-Zero and partially turned, while I waffle with this decision.  I'm leaning towards boring out the last 1.5" or so of the barrel, then porting.  This would create a "2-stage" blast chamber, the high pressure being inside the bored-out barrel, while the rear of the suppressor body itself forms the low-pressure chamber.  Thanks!

I forgot to post a basic print of the endcap, here it is in its bulky glory.  This sucker is going to weigh!

I decided to go with no porting whatsoever.  This will simplify the construction, and will also allow me to shoot with the can off of the barrel without looking like a goof, or blowing crud out the sides of the barrel.

I chucked the barrel and indicated it to run true.  The barrel OD was turned down to two diamters, one in anticipation of the threading, and the forward section, to a uniform diameter which will eventually engage a fitting inside the suppressor.






The two diameters are complete; the original 1/2 X 28 threads were parted off and the barrel is ready for threading and a crown.  The threads at the root will be 0.625" X 28; the barrel muzzle is a uniform 0.563" dia.

The threading went well.  The shoulder was cleaned up, and the threads gently wire brushed.  I can later make a thread protector for this section of the barrel for times when the can is dismounted.

There's no doubt that this is a very proprietary system, but that's OK, I certainly won't sell the suppressor, it'll be pretty much dedicated to this barrel.




An overall view, including the 11-degree "target" crown.  A good crown is essential to keep the barrel accurate and prevent flyers which can be disastrous with a mounted suppressor.


Next comes the suppressor to barrel adaptor!

Cant wait to see the end result.

More progress on the can... Again, I have decided that any form of porting on this barrel will simply add complexity and probably contribute little to suppression.  The bbl is short to begin with, and will be subsonic with most standard velocity .22LR rounds.  With a clean bbl, I can also shoot the gun unsuppressed, and it'll look good, so long as I add a thread protector to the exposed bbl threads.

With the bbl threaded, turned, and crowned, I proceeded with the root cap of the tube.  This is a section of 12L14, threaded externally to 1.593 X 24.


Drilling the end cap to a preliminary 1/2".

It is helpful to do turnings as complete as possible in a single setup.  The blank turned here is first turned down to 1.590".  Prior to threading, I worked on the bore, which will ultimately be threaded 0.563 X 28.  I have the option of later changing this "adapter" to a different female thread, such as the standard 1/2" X 28.  Thus the suppressor can be adapted in the future to a different barrel.


A common beginner error is to thread a hole in the lathe which has been only drilled, not drilled and bored.  Even the very best twist drills will wander, and the two thread sets will not be concentric with each other.  Therefore, if your bore is to be 1/2" X 28, drill first 7/16", then follow the drill with a good boring tool to open the bore to 1/2".


After the OD and ID are turned and bored, I threaded first the OD to 24 TPI.  I made use of the tube to check the progress of the threads, as I wanted this fit to be fairly stiff.  The root end cap will not be swapped often, and when installed, via a pin wrench, it'll be torqued down pretty hard, bottoming out on the 1.500" primary ID of the tube.  The "roughness" here is actually very fine swarf which cleans up easily.  12L14 is one of the easiest alloys you'll ever see for any machining operation.  Not as weldable as 1018 or 1020, though, so if you want to weld I'd avoid leaded steel.

Then, without disturbing the setup, I threaded the bore 28 TPI.  Usually, I make use of the male thread form as somewhat of a guage, but in this case I made a critical mistake.  As I approached what I knew to be the correct thread dimensions, I was unable to test fit the barrel to this piece, as the unthreaded portion of the barrel bottomed out in the bore before the threads on the barrel got to the adapter!  I did the best I could using standard shop practice, and was rewarded with a nice fit after I parted off this piece.  You do not want the suppressor to bbl thread interface to be really stiff, as the alignment comes from the bbl shoulder butting up against the end cap, rather than the threads.

Next comes the forward mounting point, which will grip the muzzle end of the bbl ~ 2" inside the tube.  It'll have bleed holes drilled into it to allow gasses to flow rearwards.

got any up dates.

Not too much, work intrudes as usual.  I've had this form 1 for a long time, and have been pondering baffles for months.  I didn't want to use straight baffles, although they'd work fine with .22LR, especially with a can this size.

I'm NOT a guru on this stuff.  I think a bit of it is intuition on what would work, but more is trial and error, and not being a manufacturer, I can't have 6 baffle stacks lying around to be tested with an expensive dB meter.  So I want to create a high performance stack from the very beginning.

I've looked hard at K-baffles, but these are tortuous to make in a lathe, and I think I've got an idea for a baffle that will perform as well, but be easier to make.  This is going to take some time... I waited 90 days for the F1, and another 10 months or so with no building, so I'm not in a rush!

In the meantime, I want to share a technique which might help withwork of this nature.  I made this brass tool to help center the bore of a badly made MkII Ruger that I wanted to thread for a CAC22.  It is very easy to center the OD of a barrel in a lathe, but what do you do when the bore itself is grossly runout?  When I indicated the OD of the Ruger bbl to zero, I could see the bore wobbling badly.  The bore's runout was probably > 0.025".  It was gross.

You cannot apply an indicator stem inside a rifled bore, so I turned this brass tool with precision.  It has a long .22 cal stem which is a wringing fit into a .22 bore.  The OD of the tool is concentric with the stem, thus if I indicate the OD of the tool, I can center the bore.  

My Kuehl bbl was better than the Ruger, but it still had some bore runout relative to the OD, so I brought the tool again into play to get the bore as centered as possible prior to turning it.

Update on the can:  I am researching and currently milling out a bafle stack.  Yes, milling!  I think I have come up with a new style of baffle that can be easily milled.  My goal is to design a baffle stack that can be produced with manual equipment much easier than a K-baffle or some other modern design.  There will be one steel baffle, and the remainder will be 2024.

I chose 2024 because of all the aluminum alloys, it exhibits the greatest strength at elevated temps.  Even 7075, which is stronger at room temperatures than 2024, has much less strength at, say, 300 to 400 degrees f.  I don't expect the baffles to ever approach that heat overall, but there may be some very quick, "localized" temperature spikes, which the body of the baffle would rapidly draw off.  Must be the copper in the 2024 which gives it this attribute.

Two questions for you guys:  The exterior tube is carbon steel.  My finishing options I think are limited to a black park, or a moly finish.  Do you think the moly would withstand the abuse?  I think I prefer a blackish park job, but I can't do that at home without investing in park equipment, and for one can that seems a bit of a goof.  

Second, the serial number.  I have a little bench CNC mill which does some sweet engraving, but it does not have a 4th axis, so engraving the tube body might look a little weird.  I'm thinking of engraving the base cap with circular lettering, like on a coin, where the lettering follows a circumference.  Would this satisfy ATF requirements, since the end caps can be removed from the body?  I've got a bad feeling that it won't, and I'll need to engrave the tube.

Since I haven't psted any pics in a while, I'll put some up out of order a bit.  Sorry about this.



When I selected the original tube, I first measured a few of the FF hand guards that I have on hand.  All of them measured 1.750 ID, meaning the tube must be < 1.75" to fit inside the guard.  Since DOM tube pretty much comes in imperial dimensions, my choices were a thick-walled 1.75" OD, requiring the can to be turned down, or a 1.625" OD can.  Since the tubing is cheap, I bought both, and decided that the 1.75" OD, after being turned down only 0.020" or so, would slide right in.

More pics:


Working on the stubby Kuehl barrel; my first step was to part off the original 1/2 X 28 thread section, since my system would be a two-point mount... this little parting tool is a mini-thin system, which are very small, very sharp, and a huge boon to a shop where one might do a lot of light parting work.  



Finally, the setup for the 11 degree crown.  The muzzle end of the barrel will ride in a boring ~0.004" larger than the bbl OD.  This slop was intentional.  A viton o-ring will create an interference fit between the bbl and the bbl bush, centering the bbl while keeping the bush from scraping and marring the bbl OD.  Viton can handle very high temperatures for a rubber-like material, and I don't think that there will be any problems.  At least, I hope not!

Finally, a basic layout of the two-point mounting.  Note the viton oring on the forward bush/washer.

Gorilla, is the area between your mount and the forward bushing part of your blast chamber? If it is I would suggest having a sleeve come back from the forward mount to the thread mount so you don't have "crud" build-up on your barrel that you will drag across your threads when removing the can.

Originally Posted By dtarbox: Gorilla, is the area between your mount and the forward bushing part of your blast chamber? If it is I would suggest having a sleeve come back from the forward mount to the thread mount so you don't have "crud" build-up on your barrel that you will drag across your threads when removing the can.

Yes that area recieves expanding gasses from the muzzle by flowback through a bolt hole circle.  The threads on the aft of the bbl (at the very end of the can) are 0.625"... the forward portion of the bbl is 0.562.  Smaller than the threads but not by a whole bunch.  I was hoping that the crud wouldn't interfere with the unscrewing of the can, but after seeing the baffle-cleaning thread with the huge amounts of gunk, I see the need for what you suggest.  I'll add it to the design.  Thanks!

Thanks dtarbox for the advice on the bbl protecting shroud.  Here is the final 2-point mount; the shroud was a simple turning of DOM tube and fits nicely.



Note that the area between the internal shroud and the bbl is simply air-space clearance.  The viton o-ring groove works perfectly.  As I mount the can to the bbl, I can feel when the bbl contacts the ring... there's a rubbery stiffness there as the bbl compresses the ring.  This forces the bbl to be concentric with tube's bore, and has the added benefit of keeping gasses from flowing back over the barrel's forward OD.  IIRC, viton is good to several hundred degrees, so I don't expect this ring to fail.  If it does, it'll be easy to replace.

The baffles are coming... bear with me, the baffles are pretty unique and I want to get their performance maximized before posting.

In the meantime, I got sick of the nasty finish on the OD of the main tube, so I decided to turn it down.  The tubing wall was pretty thick to begin with.  This was intentional, as I wanted to use 1.75" OD tube, then turn it slightly down so it would fit inside a free-float handguard.

It is occasionally hard to mount tubes of this size in a smaller lathe and achieve good finish without squall or chatter.  Because the tube is hollow, it tends to resonate, and any flex in the setup adds to the problem.

Tubing like this can be mounted in a variety of ways.  Between centers will work, but the drive dog will sometimes interfere with the operation.

My setup was simple... I turned a button of aluminum which fits into the end cap, and center-drilled the button for a live center.  That took care of the muzzle end.  I initially gripped the base end in a 6-jaw chuck, but again the chuck jaws would interfere with turning the OD.  Finally, I decided to simply use the barrel itself as a mount.  The bbl was chucked and centered; the can spun on (with no internals beyond both end caps) and the button installed into the end cap.  

With the tube mounted, I tried a variety of indexible carbide tools.  All of them sucked due to chatter and squall, despite my various feeds and speeds.  Carbide tooling is great for most setups, but the rake of most carbide tools is very low.  This makes a stronger tool, but it also requires more pressure to cut efficiently.  More pressure = deflection and chatter on a DOM tube.

Since very little metal was to be removed from the OD of the tube, on the order of 0.050", I decided to break out a ground HSS bit.  High speed cutters are often ignored in a home shop, and I think this is a mistake.  Grinding them is not difficult, and once you understand the various angles involved, you can quickly create a custom bit for top performance.  In this case, I ground a bit with a modest tip radius, very high positive rake, and fairly high side and front clearances.  What this does is create a tool which cuts with very low pressure.  The cut is continuous rather than skipping or rubbing, which low-rake tools are prone to do on carbon steel.  The main drawback is a bit of this nature can only take light cuts, on the order of 0.010" max, at least on my lathe.

This bit created an ideal finish.

Several passes were executed, and by varying the speeds and feeds, I achieved the finish I desired.  My initial thought was to polish the tube using files and/or silicon carbide paper, but if I parkerize (or moly-coat) the tube, a shiny finish is exactly what you do not want.

As I approached the desired OD of 1.700", I made a couple of practice passes and checked the finish.  What I wanted was, for lack of a better term, a "turned" finish, whereby there are turning toolmarks (grooves) that are absolutely continuous and uniform, and very minute.  From 3 feet, the tube looks bright, but closer you can see, and feel, the unpolished finish.  This style of finish will not need to be bead-blasted or prepped in any way, other than degreasing, for park or moly-coat.

I don't think I've described this very well, but it is just one way to finish off a suppressor tube among many, and I like the result.

Here it is, as turned...


The coin knurling on the end cap was turned off.  I'm not sure if I want to, but it can be restored if needed.  Bothe end caps have pin holes, and I created a pin wrench, as well as a baffle stack guide, as dedicated tools for this can.  Thus, the knurling isn't needed and would only be decorative if I added them again.

Of course, as I removed it from the lathe, I managed to drop it onto concrete.  It landed on the muzzle end and clanged it up pretty good!  It'll be easy to fix, but definitely annoying.

First, and totally off topic, my hometown in TX is the lauch community for Verizon's FIOS (fiber optic) internet service.  I went from twitchy DSL to a 15 MEGAbit fiber connection.  Man it smokes!!

On to the baffles...

Let me say again that I haven't a clue about this stuff beyond intuition and some basic references.  I haven't bought any books.  I have looked at a few pictures from various web sources.

I wanted, with this design, to avoid simply replicating a K-baffle, which would work, or even straight baffles, which work fine for large volume, .22LR cans.  Part of the concept was to generate a baffle which would automatically create annular (expansion) spaces around the baffles themselves.  In other words, the shape of the baffle, when inserted, creates 4 isolated, longitudinal regions within the suppressor, located between the baffles and the ID of the tube.  This will hopefully become clear in a moment.

First, a drawing.  I'll talk through it like it is a patent drawing.


This first image shows the basic stack shape.  It starts with round stock turned to a close sliding fit into the housing.  These blocks were carefully drilled/bored to 0.250", and the blocks (6 of them) were gathered into a stack and secured with a piece of threaded rod.  The stack was batch-processed in a vertical mill vise.  One of the benefits of this stack is a lot of the grunt work can be done in a batch like this.  The rough dimension of the blocks is 1" X 1" cube.  Note the radii on the corners which are a sliding fit into the 1.500" ID of the tube.

With the basic stack shape pictured, here is the drawing of the concept.  ALL of the cuts were made with a single end mill, 3/4" in this case, further simplifying the process.  Note that this stack is actually very easy to make, despite its complex appearance.

Note the two stacked baffle elements to the left.  The bullet passes through the bore and the first baffle.  It begins to enter the second.  The bulk of the gasses are deflected at the hemispherical cut and flow past point A.  They are redirected rearwards, and a significant amount of gas flows sideways as well, into the side chambers.  Each baffle has acute flanking cuts, so the gas, redirected at A, flows rearwards over these cuts at B, and enters the annular chambers, C, in the rightmost picture.  This diagram also shows how the baffle fits into the tube.  The shaded portion is the rearward flanking cuts.  The middle picture shows the shape of the bullet entry.

These diagrams are definitely easier to visulize by looking at the remaining photos.

A lone baffle showing the bullet entry.  This cut is created by plunging an end mill straight down.  A ball end mill would work, but plunging a good straight end mill downward removes more stock with less chatter.


This next picture shows the flanking cuts being made, again all with a 3/4" end mill.  The angle in this case is 60 degrees from centerline.  I created a simple angle fixture to position each baffle at this required angle.  The first baffle is steel; the remainder aluminum.

Each baffle has light indexing cuts on the ends, which allow the baffles to be pieced together like a puzzle.  The cuts prevent the baffles from rotating relative to each other.  This next picture clearly shows what the stack looks like when together.  The bullet path is from lower right to upper left.  You can see how (hopefully) the gas will follow a tortuous path rearwards as well as sideways into the annular chambers.




Finally, you can vaguely see the index cuts in this last picture.  the hemispherical entry chamber is obvious.  There is a lot of room for improvement with the gas flow, which I'll gladly solicit.  Suppressor gurus and manufacturers, if this stack sucks and won't work well, tell me why!  I'll try and improve it, and gladly.



For example, there is still a lot of meat on each baffle.  The sides of the baffle can be workd to improve the gas flow to the sides.  The bullet entry can have angled cuts or holes to create an assymetry common to modern baffle stacks.  Having a stocky baffle has one advantage though, it'll absorb heat well and due to the contact with the tube walls, it'll transfer the heat nicely.

This baffle is FAR easier to make than it looks.  Once the basic stack shape is made as a batch, each baffle takes 3 cuts with the same end mill... one for the hemispherical bullet entry, and two for the flanking cuts.  After I had finalized the design, the execution of a full set took about 3 hours in my shop.

I'll post some tests and impressions in the next few days.