Rules of thumb for suppressor design

Yes, it can be legal to make a silencer. For everything Form-1, from silencer designs that are easily made, to filing forms with the BATF, to 3D modeling. Remember, you must have an approved BATF Form-1 to make a silencer. All NFA laws apply.

Moderators: mpallett, bakerjw

jrmy_1
Member
Posts: 15
Joined: Tue Dec 13, 2011 10:23 pm

Rules of thumb for suppressor design

Post by jrmy_1 » Wed Mar 23, 2016 8:15 pm

Still trying to design a can. Looking for a can to work on 338RUM as well as 308win, designing for 338 RUM. Looking at using 17-4PH for everything. Will be a step cone baffle design with blast baffle. Maybe muzzle brake as well.

Anyway, looking for rules of thumb in suppressor design. Is there any overall suppressor volume or pressure rules, e.g. muffler pressure shouldn't be over XXXXpsig when bullet exits or total can volume should be XX times the volume of the bore? Similarly is there any rules for blast baffle pressure or volume? How about rules on baffle spacing?

Thanks!
J

User avatar
doubloon
Silent But Deadly
Posts: 11901
Joined: Thu Jan 01, 2009 1:02 am
Location: Houston-ish

Re: Rules of thumb for suppressor design

Post by doubloon » Wed Mar 23, 2016 8:36 pm

There is some good information in the Form 1 thread, link in my signature.
http://www.youtube.com/watch?v=BDtd2jNIwAU MUSAFAR!
http://www.youtube.com/watch?v=8CrOL-ydFMI This is Water DavidW
Complete Form 1s http://www.silencertalk.com/forum/viewtopic.php?f=10&t=79895

User avatar
LavaRed
Silent But Deadly
Posts: 1830
Joined: Sun Apr 05, 2009 8:11 pm
Location: CA

Re: Rules of thumb for suppressor design

Post by LavaRed » Wed Mar 23, 2016 10:06 pm

You'll find that so far, the only rule of thumb that's universally agreed upon is that the bore hole should be of a larger diameter than the largest caliber intended to pass through the suppressor.
Also, note that I am not joking.
"There are no stupid questions, only stupid people". -MAJ MALFUNCTION

a_canadian
Silent But Deadly
Posts: 1176
Joined: Fri Oct 11, 2013 4:09 pm

Re: Rules of thumb for suppressor design

Post by a_canadian » Thu Mar 24, 2016 1:34 am

Isn't there a second rule of thumb? The one which goes "once completed and installed, the resulting suppressor should reduce the report of the firearm noticeably." Otherwise it's not really a suppressor, more of a barrel weight. So yeah, study up on the form 1 thread. Do a bunch of Google image searches based on the caliber you're using. Build your own picture library of baffle systems you think you might be able to make. Learn why some work better than others. Make some decisions. Ask more specific questions.

User avatar
silencer_kid
Silent But Deadly
Posts: 315
Joined: Wed Jan 15, 2014 10:58 pm

Re: Rules of thumb for suppressor design

Post by silencer_kid » Thu Mar 24, 2016 8:40 am

LavaRed wrote:You'll find that so far, the only rule of thumb that's universally agreed upon is that the bore hole should be of a larger diameter than the largest caliber intended to pass through the suppressor.
Also, note that I am not joking.
.... and that 0.001" bigger than bullet size is technically sufficient, but the word "fail" is in there.

there was some new enlightening info around can design that was recently released to the public, have a look viewtopic.php?f=10&t=136461

Historian
Silent But Deadly
Posts: 3314
Joined: Mon Mar 29, 2010 11:37 pm

Re: Rules of thumb for suppressor design

Post by Historian » Thu Mar 24, 2016 9:56 am

Factoids culled from past empirical reports:

1. Diameter ≥1.5"

2. Blast chamber ≥ ⅓ length

3. First baffle symmetrical hole

4. Baffle hole diameters get 'wider' toward front.
No YAWNing, please. :)

5. Single point thread end-cap (No Red Jacket
cheap third-world-hell-hole taps)

6. Alignment rod to ensure no bad surprises prior to testing.

7. After first successful firings with noticible sound
reduction celebrate.

Best

jrmy_1
Member
Posts: 15
Joined: Tue Dec 13, 2011 10:23 pm

Re: Rules of thumb for suppressor design

Post by jrmy_1 » Thu Mar 24, 2016 7:12 pm

Thanks for help!!!!

colimr
Member
Posts: 44
Joined: Tue Oct 14, 2014 4:17 pm

Re: Rules of thumb for suppressor design

Post by colimr » Thu Mar 24, 2016 8:07 pm

Historian can you please explain the blast chamber 1/3 formula? Is it in a 10" tube blast chamber length should be 3.33" ? I have never seen or heard of a blast chamber measurement formula only a formula for internal volume capacity.Thank you

User avatar
whiterussian1974
Silent But Deadly
Posts: 2727
Joined: Sun Sep 29, 2013 12:37 am
Location: On 8th line of eye chart.

Re: Rules of thumb for suppressor design

Post by whiterussian1974 » Thu Mar 24, 2016 10:10 pm

colimr wrote:Historian can you please explain the blast chamber 1/3 formula? Is it in a 10" tube blast chamber length should be 3.33" ? I have never seen or heard of a blast chamber measurement formula only a formula for internal volume capacity.Thank you
He can answer for himself. Though I disagree.

There are many designs which have 1/8L or less. For .22lr you want the smallest possible to combat FRP. There was a recent thread showing a monocore w gradually increasing chamber sizes. The 1st 2 were tiny and next were not much bigger. Interesting Theory for that which was demonstrated w utube vid.

Biggest reason for large 1st chamber is to allow gas to exand to point where heat*pressure is low enough for material to function. Otherwise thickness might need to be 4-8x standard. Though I personally prefer the 1st chamber to have 50%+ greater thickness than remainder of build.
The Darkest Corners of Hell are reserved for those who remain Neutral!-Dante
The Death of One is a Tragedy, a million only a statistic.-Stalin
Well I AM 1/16 Demon on my Father's Side!-Dresden Files

User avatar
LavaRed
Silent But Deadly
Posts: 1830
Joined: Sun Apr 05, 2009 8:11 pm
Location: CA

Re: Rules of thumb for suppressor design

Post by LavaRed » Thu Mar 24, 2016 11:28 pm

colimr wrote:Historian can you please explain the blast chamber 1/3 formula? Is it in a 10" tube blast chamber length should be 3.33" ? I have never seen or heard of a blast chamber measurement formula only a formula for internal volume capacity.Thank you
Years ago I came up with that rule, and it always applied to centerfire suppressors. Rimfires should be kept at least 1/6 of empty internal volume. And at any rate it's not really set in stone. It's more important to avoid exactly 1/4 of internal volume. It tends to make the can resonate.
"There are no stupid questions, only stupid people". -MAJ MALFUNCTION

User avatar
whiterussian1974
Silent But Deadly
Posts: 2727
Joined: Sun Sep 29, 2013 12:37 am
Location: On 8th line of eye chart.

Re: Rules of thumb for suppressor design

Post by whiterussian1974 » Thu Mar 24, 2016 11:35 pm

LavaRed wrote:It's more important to avoid exactly 1/4 of internal volume. It tends to make the can resonate.
1/2, 1/4, 1/8, 1/16. It makes sense. Periodic nodes.

https://en.wikipedia.org/wiki/Harmonic
Image
The Darkest Corners of Hell are reserved for those who remain Neutral!-Dante
The Death of One is a Tragedy, a million only a statistic.-Stalin
Well I AM 1/16 Demon on my Father's Side!-Dresden Files

quietoldfart
Senior Silent Operator
Posts: 104
Joined: Mon Jan 27, 2014 4:28 pm
Location: France

Re: Rules of thumb for suppressor design

Post by quietoldfart » Thu Mar 24, 2016 11:47 pm

I have settled on a gap from crown to first baffle entry (a sharp-nosed simple hemi-toroidal blast baffle with 1/16" Dater hole) of 0.55". The K baffles in that pistol suppressor are likewise 0.55" long and there are 7 of them, so 4.4" + the 0.315" deep blast baffle, for a total gap between muzzle and contoured end cap of 4.715". That makes my blast chamber volume about 11.7% of the total length, or a fraction of about 2/17ths. I've detected no FRP either by ear or by (admittedly awfully cheap, but remarkably reliable and consistent) meter. I can depend upon my pistol suppressor emitting no more noise from one shot to the next... unless using Remington ammunition, which seems to be very inconsistently loaded with powder. I have similarly found no FRP with my takedown rifle suppressor, but wouldn't expect it there as it is a 10" ported barrel reflex design. Having tested a number of patterns of K baffles and various, gradually shortening lengths of first OTB suppressors with porting (when the pistol had a 7" barrel) and then threaded-on models (after shortening it to 4") I have yet to hear or record any significant FRP. The most notable exception was with an OTB suppressor about 11" long, 8" of that ahead of the muzzle, using 6 K baffles about 1.125" long with rather bad porting and no blast baffle, with about a 0.5" spacer before the first one. In that case I was seeing between 1.5dB and 2.3dB of volume increase. But the whole thing was too loud, an awful K design with a long waist and long cones. Shorter K baffles seem to be the ticket for rimfire.

Historian
Silent But Deadly
Posts: 3314
Joined: Mon Mar 29, 2010 11:37 pm

Re: Rules of thumb for suppressor design

Post by Historian » Fri Mar 25, 2016 7:56 am

LavaRed wrote:
colimr wrote:Historian can you please explain the blast chamber 1/3 formula? Is it in a 10" tube blast chamber length should be 3.33" ? I have never seen or heard of a blast chamber measurement formula only a formula for internal volume capacity.Thank you
Years ago I came up with that rule, and it always applied to centerfire suppressors. Rimfires should be kept at least 1/6 of empty internal volume. And at any rate it's not really set in stone. It's more important to avoid exactly 1/4 of internal volume. It tends to make the can resonate.
+1

Indeed factoid remembered from LavaRed's past great posts.

In addition this rule was dependent on baffle topology, spacing,
and tube diameter versus length ratio.

For example the classic Parker Hale 1930's .22 dimensions were
as best remembered: I.D. .75" (US pennies fit in),length ~ 6.5",
dimpled disks, blast chamber seemed to be in ⅓ range.

Like all 'rule of thumb' when misapplied one sometimes winds up
with a hammer hit and a cartoon pulsating red bulb. :)

The new Ruger Silencer's specs and baffle topology now sets the rule for .22.

Best, LavaR.

User avatar
LavaRed
Silent But Deadly
Posts: 1830
Joined: Sun Apr 05, 2009 8:11 pm
Location: CA

Re: Rules of thumb for suppressor design

Post by LavaRed » Fri Mar 25, 2016 1:30 pm

Historian wrote:+1

Indeed factoid remembered from LavaRed's past great posts.

In addition this rule was dependent on baffle topology, spacing,
and tube diameter versus length ratio.

For example the classic Parker Hale 1930's .22 dimensions were
as best remembered: I.D. .75" (US pennies fit in),length ~ 6.5",
dimpled disks, blast chamber seemed to be in ⅓ range.

Like all 'rule of thumb' when misapplied one sometimes winds up
with a hammer hit and a cartoon pulsating red bulb. :)

The new Ruger Silencer's specs and baffle topology now sets the rule for .22.

Best, LavaR.
I haven't seen the new Ruger silencer, having been out of the loop for a while. What's it like?
"There are no stupid questions, only stupid people". -MAJ MALFUNCTION

a_canadian
Silent But Deadly
Posts: 1176
Joined: Fri Oct 11, 2013 4:09 pm

Re: Rules of thumb for suppressor design

Post by a_canadian » Fri Mar 25, 2016 1:37 pm

Like this. Cast in stainless.

Image

User avatar
Capt. Link.
Silent But Deadly
Posts: 2594
Joined: Wed Oct 17, 2007 10:05 pm
Location: USA.

Re: Rules of thumb for suppressor design

Post by Capt. Link. » Fri Mar 25, 2016 4:34 pm

While this depends on several factors such as host the importance of a initial blast chamber is highly over rated.Even for gas operated guns back pressure can be held to a minimum if the blast baffle is close to the muzzle and the next baffle is spaced wide.With locked breech weapons a chamber of virtually none can be used.The requirement is a sturdy blast baffle with any short chambered suppressor.

You can also go to the other extreme with a huge blast chamber.While many shy away from this designs exist that will eliminate FRP to take advantage of the very long life a baffle can have if spaced far away from the hosts muzzle.

One of the most promising is the middle ground where a muzzle brake is used as a sacrificial blast baffle.The brake attached to the host is also a thread adapter and thus replaceable as it wears out in compliance with US law.Using this you can go either way with a short or long chamber.If your building for supersonic ammo the replaceable brake and longish chamber will probably put you in a favorable position as it will never be truly silent.

Lava's rule of the bore needing to be larger than the bullet is the only one I know that must be adhered to. :D
A + .060 over bullet size is a good basic rule.This allows for a little baffle induced yaw and differences in ammo.The OAL of the suppressor and your ability to hold runout are also key factors.

Welcome to the group-CL
The only reason after 243 years the government now wants to disarm you is they intend to do something you would shoot them for!

User avatar
Capt. Link.
Silent But Deadly
Posts: 2594
Joined: Wed Oct 17, 2007 10:05 pm
Location: USA.

Re: Rules of thumb for suppressor design

Post by Capt. Link. » Fri Mar 25, 2016 5:35 pm

a_canadian wrote:Like this. Cast in stainless.

Image
I must complement a_canadian for this most wonderful sculpture.
The only reason after 243 years the government now wants to disarm you is they intend to do something you would shoot them for!

User avatar
LavaRed
Silent But Deadly
Posts: 1830
Joined: Sun Apr 05, 2009 8:11 pm
Location: CA

Re: Rules of thumb for suppressor design

Post by LavaRed » Fri Mar 25, 2016 5:38 pm

Well, then again there are suppressors with wipes, where the bore is smaller than the bullet, so even that is not 100% fixed.
"There are no stupid questions, only stupid people". -MAJ MALFUNCTION

a_canadian
Silent But Deadly
Posts: 1176
Joined: Fri Oct 11, 2013 4:09 pm

Re: Rules of thumb for suppressor design

Post by a_canadian » Fri Mar 25, 2016 5:40 pm

Not mine! That's just the nicest picture I could find with a Google image search for Ruger's new suppressor baffles. But yes, it is a lovely picture conveying the nature of the thing nicely.

User avatar
Capt. Link.
Silent But Deadly
Posts: 2594
Joined: Wed Oct 17, 2007 10:05 pm
Location: USA.

Re: Rules of thumb for suppressor design

Post by Capt. Link. » Fri Mar 25, 2016 5:48 pm

You get a ata-boy for finding and posting. 8)

Great to see you back Lava how is it in sunny CA :D
The only reason after 243 years the government now wants to disarm you is they intend to do something you would shoot them for!

User avatar
LavaRed
Silent But Deadly
Posts: 1830
Joined: Sun Apr 05, 2009 8:11 pm
Location: CA

Re: Rules of thumb for suppressor design

Post by LavaRed » Fri Mar 25, 2016 8:33 pm

Capt. Link. wrote:You get a ata-boy for finding and posting. 8)

Great to see you back Lava how is it in sunny CA :D
Extremely hot. In the 80's. I'm suffering. :)
"There are no stupid questions, only stupid people". -MAJ MALFUNCTION

User avatar
doubloon
Silent But Deadly
Posts: 11901
Joined: Thu Jan 01, 2009 1:02 am
Location: Houston-ish

Re: Rules of thumb for suppressor design

Post by doubloon » Sat Mar 26, 2016 7:13 am

Sounds like mini-skirt weather.
http://www.youtube.com/watch?v=BDtd2jNIwAU MUSAFAR!
http://www.youtube.com/watch?v=8CrOL-ydFMI This is Water DavidW
Complete Form 1s http://www.silencertalk.com/forum/viewtopic.php?f=10&t=79895

User avatar
T-Rex
Silent But Deadly
Posts: 1864
Joined: Wed Oct 29, 2014 4:38 pm
Location: CT - The AntiConstitution State

Re: Rules of thumb for suppressor design

Post by T-Rex » Sat Mar 26, 2016 8:28 am

doubloon wrote:Sounds like mini-skirt weather.
Not always a good thing.
Last edited by T-Rex on Sat Mar 26, 2016 1:32 pm, edited 1 time in total.
Completed Builds www.silencertalk.com/forum/viewtopic.php?t=79895
Burst Calculator www.engineersedge.com/calculators/pipe_bust_calc.htm
Silencer Porn www.instagram.com/explore/tags/silencerporn/

Historian
Silent But Deadly
Posts: 3314
Joined: Mon Mar 29, 2010 11:37 pm

Re: Rules of thumb for suppressor design

Post by Historian » Sat Mar 26, 2016 11:24 am

a_canadian wrote:Like this. Cast in stainless.

Image
Inspired by the amazing metal smiths such as Jesse James & Jerry Fisk*, I
pondered if a close approximation to this shape could be arrived at starting
hammer forging from 60º cone baffle on a machined cylinder. Gedanken forging
requirements would include making a die to fit the cylinder with a central
rod preserving the hole integrity. The homotopy deformation from hammering
would give 'ripples' not found in the commercial baffle. How would the
smiths of old make such a shape?


*<< https://www.youtube.com/watch?v=Y_DTKASREEM >>
<< http://www.knifetreasures.com/viewKnife ... ed_menu=13 >>

User avatar
gunny50
Silent But Deadly
Posts: 784
Joined: Wed Jan 23, 2008 7:11 am
Location: EU

Re: Rules of thumb for suppressor design

Post by gunny50 » Sat Mar 26, 2016 11:55 am

"Historian"

Cut pipe with 45 / 60 degree angle, than heat tred hot in Kiln, and forge over a mandril with the right inner shape.

Gunny
http://www.silencertalk.com/forum/viewtopic.php?f=10&t=135514
http://www.silencertalk.com/forum/viewtopic.php?f=10&t=79895
http://www.silencertalk.com/forum/viewtopic.php?f=10&t=77913

Post Reply