Rimfire internals - Design exposition

[T-Rex]

The following designs pertain to a certain firearm, but my questions and ideas are for rimfire and lower pressure rounds, in general.
The said firearm is a 4.5", 22lr on an AR15 platform. Already stamped for SBR.
It has a 4, YHM, lightweight handguard mounted to it.
I would like a 1.625", OD suppressor tube to be the "look" and not extending more than 6" from the handguard. The standard SD look.
I could easily do a 1" OD x 5-6" standard K baffle design, tucked inside a faux, 1.625" shell, but if I can use this internal volume, why not.
I do not wish to port the barrel.

The top design has a 1" OD tube w/ 7, K-Baffles inside of it. After the muzzle and before the blast baffle are ports to vent into the space between the outer and inner tubes.

The bottom design uses the same K-Baffles, exact design and total number. Instead of a tube to contain them, they are pressed into bushings to bring their OA OD to fit into the outer tube. The same, essential, porting design is used before the blast baffle to allow the over-barrel area for gas expansion. I did this so as not to waste material and keep the number of baffles greater than the length of each individual baffle.



Regardless of what design aspects need to be changed, currently (we can discuss that after initial idea is decided):

Which design do you see providing a more effective use of space, netting a greater overall noise suppression?
Do you see either of these designs having useful function on platforms other than the one mentioned?

[Samson104]

So what over all length are you looking for?
I think K's at 1.375"+ in diameter are gonna be kinda long if you want a short can.
you could do a 8" can witch will only stick out 2" or so past a 10" hand guard

[T-Rex]

So what over all length are you looking for?
Not to be >6" past the bbl
I think K's at 1.375"+ in diameter are gonna be kinda long if you want a short can.
That is why they are for a 1"OD tube with bushings for the larger tube. Both designs are dimensionally identical as far as OD and Length.
you could do a 8" can witch will only stick out 2" or so past a 10" hand guard
The platform is a 4.5" bbl w/ 4" FF handguard.

[whiterussian1974]

My 1st impression is that Top is better. But, bottom reminds me of Omega baffle concept.
Top coaxial space acts like a large sump that acts like a slowly filling blast chamber. (Minimizing FR pop and retaining the air longer.)
But the cross jetting in the bottom might work better than a large initial sump.

In the end, I cant' guess which would perform better. Only testing would help determine which design concept is best.
If barrel porting was used, the top would work better. But as posted, either could outperform the other. It really comes down to the details of the venting interface after gases leave the barrel.

[whiterussian1974]

The longer that I look, I think that the low pressure of .22lr wouldn't fill the coaxial space of the top very well. So, bottom would probably retain gas longer.
I would recommend the bottom. And the only major tweek that i'd recommend would be changing the orange endcap. There should be a 3/8" "snorkel" going up into the previous K's skirt. Then port the exit holes away through it. That would help retain gas inside longer and smooth the gas exiting the tube.
As for use on other platform: I'd imagine that they'd be good on most .22lr hosts. Just more complicated than most builders would want to attempt.
Just some observations.

[BCJ]

Realistically anything you do with that much volume is going to be quiet for a 22. You'll have first round pop though unless you make a small blast chamber.
I made a 1.25" OD x 5" suppressor for my 10/22 since I wanted something that looked better than the standard 1" od suppressor. I just used cones at 0.5" spacing and it as stupid quiet

[Historian]

The following designs pertain to a certain firearm, but my questions and ideas are for rimfire and lower pressure rounds, in general.
The said firearm is a 4.5", 22lr on an AR15 platform. Already stamped for SBR.
It has a 4, YHM, lightweight handguard mounted to it.
I would like a 1.625", OD suppressor tube to be the "look" and not extending more than 6" from the handguard. The standard SD look.
I could easily do a 1" OD x 5-6" standard K baffle design, tucked inside a faux, 1.625" shell, but if I can use this internal volume, why not.
I do not wish to port the barrel.

The top design has a 1" OD tube w/ 7, K-Baffles inside of it. After the muzzle and before the blast baffle are ports to vent into the space between the outer and inner tubes.

The bottom design uses the same K-Baffles, exact design and total number. Instead of a tube to contain them, they are pressed into bushings to bring their OA OD to fit into the outer tube. The same, essential, porting design is used before the blast baffle to allow the over-barrel area for gas expansion. I did this so as not to waste material and keep the number of baffles greater than the length of each individual baffle.



Regardless of what design aspects need to be changed, currently (we can discuss that after initial idea is decided):

Which design do you see providing a more effective use of space, netting a greater overall noise suppression?
Do you see either of these designs having useful function on platforms other than the one mentioned?

Gut feeling:

Second design with full diameter K's.

Perforate blast chamber tube and wrap with bronze
mesh to allow initial gas expansion while
adding time delays.

[Bendersquint]

Top will perform better than the bottom one.

[Historian]

Top will perform better than the bottom one.

I definitely would trust Mr. B. any and all times.

Brains and experience over good looks and age.

Seriously, it would be most interesting to make a measurable
comparison. Lava?

[T-Rex]

Realistically anything you do with that much volume is going to be quiet for a 22. You'll have first round pop though unless you make a small blast chamber.
I made a 1.25" OD x 5" suppressor for my 10/22 since I wanted something that looked better than the standard 1" od suppressor. I just used cones at 0.5" spacing and it as stupid quiet

Your thoughts on volume being a plus are exactly why I wanted to use all that available space.

I know there aren't any dimensions in the design drawing, but the distance from muzzle to blast baffle face is 0.234" and it is a cone so you can deduct even more volume.
My thoughts on FRP are this:
The large coaxial and over-barrel spaces for cooling and expansion would act almost like an integral with ports after the chamber.
There is a small chamber, after the muzzle, for initial turbulence and redirection into the outer chambers.

Top will perform better than the bottom one.

Would you mind going into a bit of detail.
While I appreciate a positive answer from a knowledgeable party, understanding the hows and whys will aid in future designs.

In the OP, I also asked:
Do you see either of these designs having useful function on platforms other than the one mentioned?

What are your thoughts on this aspect?

[LavaRed]

Top will perform better than the bottom one.

I definitely would trust Mr. B. any and all times.

Brains and experience over good looks and age.

Seriously, it would be most interesting to make a measurable
comparison. Lava?

Off the top of my head, I would say the first one will perform better because the gases have more pressure at the blast chamber, before being diverted towards the coaxial space, than at every individual baffle being diverted into an increased chamber. Also, the coaxial chamber gives a far longer delay for gases to return to the bullet path, while on the second design, there's nothing preventing the gases to return to the bore stream. I would add packing to both the over-barrel portion and the coaxial chamber to act as a filler and add delay. Else your FRP will be horrendous. Try scotch-brite pads, or paint-scrubber pads if you don't care much for the lemony smell. They tend to last an insane amount of time.

I apologize that I probably won't be able to have working prototypes of both built for testing right away. Between everyday life, and my new gun/silencer project, I'll probably have my plate full for most of the year. But it will be worth it, I hope.

[T-Rex]

Thank you for your reply.
Some questions.

Off the top of my head, I would say the first one will perform better because the gases have more pressure at the blast chamber, before being diverted towards the coaxial space,
Why would there be an increased pressure from one to the other if both blast chambers are designed equally?
If design #1 has larger coaxial chambers, wouldn't that create a lower pressure in the blast area quicker than design #2?
Also, the coaxial chamber gives a far longer delay for gases to return to the bullet path, while on the second design, there's nothing preventing the gases to return to the bore stream.
Understood. I agree and this is one reason I envisioned design #1 first.
I would add packing to both the over-barrel portion and the coaxial chamber to act as a filler and add delay. Else your FRP will be horrendous.
Why would FRP be louder than a 16" integral with porting immediately after the chamber?
Try scotch-brite pads, or paint-scrubber pads if you don't care much for the lemony smell. They tend to last an insane amount of time.
Are you suggesting the green or brown pads?
Do you put them in there tightly packed or loose? (what percentage of fill?)
Do you pull them apart, slightly, before packing?

Thanks again for the input.

[LavaRed]

Thank you for your reply.
Some questions.

Off the top of my head, I would say the first one will perform better because the gases have more pressure at the blast chamber, before being diverted towards the coaxial space,
Why would there be an increased pressure from one to the other if both blast chambers are designed equally?
If design #1 has larger coaxial chambers, wouldn't that create a lower pressure in the blast area quicker than design #2?
Also, the coaxial chamber gives a far longer delay for gases to return to the bullet path, while on the second design, there's nothing preventing the gases to return to the bore stream.
Understood. I agree and this is one reason I envisioned design #1 first.
I would add packing to both the over-barrel portion and the coaxial chamber to act as a filler and add delay. Else your FRP will be horrendous.
Why would FRP be louder than a 16" integral with porting immediately after the chamber?
Try scotch-brite pads, or paint-scrubber pads if you don't care much for the lemony smell. They tend to last an insane amount of time.
Are you suggesting the green or brown pads?
Do you put them in there tightly packed or loose? (what percentage of fill?)
Do you pull them apart, slightly, before packing?

Thanks again for the input.

No, what I meant was that the gases have more pressure at the blast chamber than farther down the stack, for both designs, so it's easier to get them to expand into the extra volume at the blast chamber, than later on in little increments. There's a point of diminishing returns in terms of extra diameter, and for .22LR, that's about 1.25" ID. With a ported integral, the ports themselves diffuse the gas enough that there is no major boom from unburnt powder and shockwave, but in a largely empty chamber, this will happen. The packing will do the same thing the porting does.
Either green or brown pads work well. The brown ones might last a smidgen longer, but it's not really significant. You should cut them to size and then roll them concentrically around the over-barrel extension and the coaxial tube, tightly. A bit like making sushi.

[T-Rex]

No, what I meant was that the gases have more pressure at the blast chamber than farther down the stack, for both designs, so it's easier to get them to expand into the extra volume at the blast chamber, than later on in little increments.
Yes, that makes sense, when read like that.
There's a point of diminishing returns in terms of extra diameter, and for .22LR, that's about 1.25" ID.
Diminished is ok, as long as it is not nullifying.
I want the SD look so the extra space is welcomed.
With a ported integral, the ports themselves diffuse the gas enough that there is no major boom from unburnt powder and shockwave, but in a largely empty chamber, this will happen.
Would I benefit more from directing the initial gas release into the coaxial chamber rather than the reflex?
I could try to make it so, upon return, they slip to the reflex before returning to exit flow path.
Would the effort be more than the result?
The packing will do the same thing the porting does.
Either green or brown pads work well. The brown ones might last a smidgen longer, but it's not really significant. You should cut them to size and then roll them concentrically around the over-barrel extension and the coaxial tube, tightly.
Easy enough.
A bit like making sushi.
Ah, yes, I know this one.

[LavaRed]

No, what I meant was that the gases have more pressure at the blast chamber than farther down the stack, for both designs, so it's easier to get them to expand into the extra volume at the blast chamber, than later on in little increments.
Yes, that makes sense, when read like that.
There's a point of diminishing returns in terms of extra diameter, and for .22LR, that's about 1.25" ID.
Diminished is ok, as long as it is not nullifying.
I want the SD look so the extra space is welcomed.
With a ported integral, the ports themselves diffuse the gas enough that there is no major boom from unburnt powder and shockwave, but in a largely empty chamber, this will happen.
Would I benefit more from directing the initial gas release into the coaxial chamber rather than the reflex?
I could try to make it so, upon return, they slip to the reflex before returning to exit flow path.
Would the effort be more than the result?
The packing will do the same thing the porting does.
Either green or brown pads work well. The brown ones might last a smidgen longer, but it's not really significant. You should cut them to size and then roll them concentrically around the over-barrel extension and the coaxial tube, tightly.
Easy enough.
A bit like making sushi.
Ah, yes, I know this one.

With the volumes involved, there won't be any noticeable added benefit from redirecting into the reflex chamber over the coaxial. However, the fact that I see no inner tube isolating the barrel from the reflex chamber means that unless there is a tight seal at the back, gases can escape and make noise. I would add a thin tube here to completely enclose the reflex chamber. Then you can enlarge the ports that lead into it (they're too small), and all will be good.

Or, you could eliminate the reflex chamber and save some weight (again, with the volumes and pressures involved it would hardly contribute any additional suppression), or you could simply use a non-reflex suppressor of the same length with several more K's, which will definitely contribute additional suppression.

[whiterussian1974]

My thoughts on FRP are this:
The large coaxial and over-barrel spaces for cooling and expansion would act almost like an integral with ports after the chamber.
There is a small chamber, after the muzzle, for initial turbulence and redirection into the outer chambers.

The 1st K will generate FRP. Very little gas will pass from blast chamber into coaxial space b/f unburnt powder enters baffle stack. And the O2 in Ks will allow remaining powder to burn w/o choking off the sound as a true integral would. (By forcing the gas to return to barrel after expanding and cooling in coax.)

[whiterussian1974]

Would removing the purple K and substituting a ported tube help reduce FRP?
It seems that cooling and expanding gas to prevent continued burning is the best way.
The "pineapple/pinecone" design works on this principle.
But only use the 1st segment.

Maximizing surface area in 1st chamber lowers temp w/o introducing O2 like an expansion chamber would. Then expansion zones work great w/o generating FRP.

The biggest ? is whether you are able to get enough gas into the coax prior to gas exitting the baffle stack. That's the big ? b/t your 2 ideas.
That's why I voted for Bottom in my "Mon Jan 26, 2015 7:49 pm Post." If you change the porting to allow faster evacuation into the coax, then my vote changes to Top.
You need to maximize the airflow into the coax, then restrict its return. Otherwise, the volume is wasted b/c gas is already exitting the can b/f the coax is filled.

LavaRed: the lavander plug at rear seems to be either 2point mount or barrel bushing to block escaping gas. You're right. It should be threaded for best performance. Though even a tight fitting soft bushing (synthetic rubber) should work for a .22lr.
Heck, even PVC has worked on builds that I've seen shot at the Range. (And YES. ATF F1 paperwork included.) Though the hosts were minimum 10" bbl. I've only seen metal used for pistol builds.

[Bendersquint]

Would removing the purple K and substituting a ported tube help reduce FRP?
It seems that cooling and expanding gas to prevent continued burning is the best way.
The "pineapple/pinecone" design works on this principle.
But only use the 1st segment.

Maximizing surface area in 1st chamber lowers temp w/o introducing O2 like an expansion chamber would. Then expansion zones work great w/o generating FRP.

Not it wouldn't do anything to mitigate FRP,

[whiterussian1974]

Not it wouldn't do anything to mitigate FRP,

What would you recommend?
Do you agree that the coaxial space wouldn't properly fill b/f gas began exiting the suppressor? So the volume isn't fully effective as designed.
What should Author change in his design?

[curtistactical]

For some reason I feel I am going to be sorry for getting in on this but here's my .02 . Being it is a .22 I think having the reflex will hurt you more than helping. My reasoning for this is you are not dealing with much gas in the first place so stripping gas off before it enters the K's is not necessary. I would use the first design minus the ports for the reflex portion and you will have pretty much no FRP and it will be extremely quiet. Our rim fire suppressor uses six k baffles with hardly no blast chamber and it is extremely quiet, the testing I have done with it reveals avg. of 116db FRP with 112db following shots on a walther p22 using CCI standard velocity ammo, the only rim fire suppressors I have metered lower are our 10/22 and MKIII integral while holding the actions closed on them. For center fire calibers the information I just gave would be totally different however.

[T-Rex]

For some reason I feel I am going to be sorry for getting in on this but here's my .02 .
Not at all, your input is very much appreciated
Being it is a .22 I think having the reflex will hurt you more than helping. My reasoning for this is you are not dealing with much gas in the first place so stripping gas off before it enters the K's is not necessary.
Understood. This is one of the reasons I stated the entire interior volume was at the projects disposal, whether needed or not. I want the SD look, sothe rear portion can be hollow, no problem.
I would use the first design minus the ports for the reflex portion and you will have pretty much no FRP and it will be extremely quiet.
Are you including the coaxial space around the baffles as part of the reflex? It sounds like you would remove this portion as well.
Our rim fire suppressor uses six k baffles with hardly no blast chamber and it is extremely quiet, the testing I have done with it reveals avg. of 116db FRP with 112db following shots on a walther p22 using CCI standard velocity ammo, the only rim fire suppressors I have metered lower are our 10/22 and MKIII integral while holding the actions closed on them.
Yeah, the Ciener bolts aren't that quiet and don't have any dampening.
For center fire calibers the information I just gave would be totally different however.
This leads to one of the questions I asked in the OP.
What platform, if any, do the designs, as or close to as drawn, fit into?
9mm, 45, other blowback designs?
I'm planning it, currently, for a 22, but where is the limit?
The interior parts can be modified/redesigned.

From the ideas that have been brought forth, thus far, it seems the first design is definitely the avenue to pursue.
We are also learning that volume isn't always our friend, not even effective use of it.
I'm going to make some design changes and get back here.

Keep thinking

[curtistactical]

The coaxial space around the baffles is good in the first drawing since you have the 1" tube over the baffles, I think the volume of the coaxial space on the second drawing would be too much for a .22 (When I am speaking of the coaxial area I am talking the space that the K baffle vents into with the mouse hole) I would not use the empty space outside the 1" tube at all. I think your second drawing might actually work well for something like a 9mm AR if you were to bump the OD of the K's up to 1.25", this is something I would have interest in trying vs full diameter K's since you can fit more of the smaller diameter baffles in a given length. The reflex design would work good with pistol calibers also I believe.

[T-Rex]

I would not use the empty space outside the 1" tube at all.

So, just a 1" suppressor w/ 7, K-Baffles hidden inside a larger tube.

this is something I would have interest in trying vs full diameter K's since you can fit more of the smaller diameter baffles in a given length. The reflex design would work good with pistol calibers also I believe.

This is exactly why I designed it with the bushings.
Larger for 9mm makes sense.

The reflex design would work good with pistol calibers also I believe.

The entire empty space or just the rear portion?

Thanks

[curtistactical]

Yep for the 22 I would just have the 1" inside the tube. For the pistol caliber I like the second design using the rear as a reflex and using the full diameter of the tube at the K baffles, pretty much exactly how you have number two drawn.

[T-Rex]

Yep for the 22 I would just have the 1" inside the tube. For the pistol caliber I like the second design using the rear as a reflex and using the full diameter of the tube at the K baffles, pretty much exactly how you have number two drawn.

Thanks for the critique.
I was hoping the extra volume could've been effective, but if not oh well.

I'm sure I'll be happy with 5" worth of Ks.