New to the trade, did some reading and have some questions

[Alpha_Stigma]

Hello, as the title says I'm new to silencer smithing and have been doing some reading. About me; I'm an engineer, but don't have my own mill (anymore) or lathe at this time so am mostly practicing designing/modeling/simulating some silencer ideas that I've gathered up before biting the bullet on paperwork.

After reading this rundown..

1) I haven't found a good method for calculating the gas pressure at the end of a silencer. Primarily interested in 5.56. Using the equation PV/T=PV/T was my first approach but I don't know the relative temp drop and i'm sure more factors are at play. (this has caused me the most head aches tbh) I think this is one of the most important factors when deciding material to use.

2) Any hard and fast rules for baffle spacing?

3) From what I understand the equipment to test the short db burst of a rifle is quite expensive. Are there any known services or work around to get a good idea what db a can is operating at?

4) Why should you never use a crush washer to mount a muzzle device to your host that will also be used on a silencer? Is it because you may have uneven movement when clocking?


Thanks in advance for any help

[partsguy22]

Welcome
1)something something expanding gasses, open chamber something something temp drop...yeah someone with more knowledge than me can probably explain it better
2) No... there are to many variables depending on baffle design , suppressor volume , barrel length of the host , amount of gas (depending on cartrage and load specifics)
3)Not that I know of
4)crush washers do not crush evenly an can reek havoc on bore alignment resulting in bad accuracy at best and baffle strikes at worse.

[fishman]

Hello, fellow engineer.

1)dont.

PV/T is not a law of physics, its an aproximation. We are dealing with temperatures and pressures WELL outside the scope of that approximation. In adition to that, the fluid dynamics going on dont make the pressure in the blast chamber uniform or calculate-able.

Also, forget modeling fluid dynamics in a silencer. Without a supercomputer and specialized software, you arent even gonna get close. I have steady state flow analysis on my 300 blk silencer using solidworks. Its not really good for much beyond having a picture with swirly gasses and pretty colors.


2) no. Everyone has their own theories. Some say uniform spacing. Some say increasing spacing. Some say decreasing. Some say uniform except for throw an odddball length spacer somewhere in the middle.

Generally speaking: more baffles = more gooder. It also makes the can heavier. There is diminishing return with each baffle you add. Low pressure rounds need more baffles than high pressure rounds.

3) correct. Its a very complicated topic. Some people want the gun to sound quiet, which requires a nice tone. This could be so that they can shoot without disturbing neighbors, or wild animals. Some only care about hearing damage, so the only place that makes any sense to measure sound is at the ear, and tone doesnt really matter.

A cell phone decibel meter wont measure well up close, but from a distance, say 25 yards, it can give you a pretty good idea of which silencer of two is quieter. I wouldnt bother unless you're going to go all out, or go to a community silencer metering event.

4) crush washers dont crush uniformly. They can cause silencer misalignment. Slight misalignment will mess up your accuracy. More misalignment will damage your silencer.

[Capt. Link.]

Welcome
1)something something expanding gasses, open chamber something something temp drop...yeah someone with more knowledge than me can probably explain it better

You got it right but forgot mousehole, port and sidewall with ablative on the side.....err

OP welcome to the obsession.....of suppression.

[Alpha_Stigma]

Hello, fellow engineer.

1)dont.

PV/T is not a law of physics, its an aproximation. We are dealing with temperatures and pressures WELL outside the scope of that approximation. In adition to that, the fluid dynamics going on dont make the pressure in the blast chamber uniform or calculate-able.

Also, forget modeling fluid dynamics in a silencer. Without a supercomputer and specialized software, you arent even gonna get close. I have steady state flow analysis on my 300 blk silencer using solidworks. Its not really good for much beyond having a picture with swirly gasses and pretty colors.


2) no. Everyone has their own theories. Some say uniform spacing. Some say increasing spacing. Some say decreasing. Some say uniform except for throw an odddball length spacer somewhere in the middle.

Generally speaking: more baffles = more gooder. It also makes the can heavier. There is diminishing return with each baffle you add. Low pressure rounds need more baffles than high pressure rounds.

3) correct. Its a very complicated topic. Some people want the gun to sound quiet, which requires a nice tone. This could be so that they can shoot without disturbing neighbors, or wild animals. Some only care about hearing damage, so the only place that makes any sense to measure sound is at the ear, and tone doesnt really matter.

A cell phone decibel meter wont measure well up close, but from a distance, say 25 yards, it can give you a pretty good idea of which silencer of two is quieter. I wouldnt bother unless you're going to go all out, or go to a community silencer metering event.

4) crush washers dont crush uniformly. They can cause silencer misalignment. Slight misalignment will mess up your accuracy. More misalignment will damage your silencer.

Hey thanks for the reply!

Yea I'm honestly just trying to get in the ball park that's why I thought id give it a shot. Purpose being If i know my pressure I can get a good idea of my factor of safety. I've done some searching and only found pressures in the barrel, do you know if there are some approximations? Finding the yield strength of steel at varying temps has been a nightmare as well...

Also I like your swirly lines!

[T-Rex]

Don't get too hung up on the pressure and safety (I say this lightly). A suppressor is never a sealed vessel and doesn't need to be treated as one. Stick to some of the more popular wall thicknesses, ie .065, and you'll be fine. Some have gone so thin as ~.01 (I believe in 316 or 304) and used on a centerfire rifle.

If you haven't already, click on the completed builds thread (link in my sig) and peruse through there. It covers many years of silencer building, both theory and application.

[cdhknives]

I have idly wondered about inside pressures and thought the strain gauge type barrel pressure sensors would work fine for a suppressor. BUT, with all the good experimental data from the multitude of completed (and occasionally blown up) builds out there, my thought quickly passed. Thankfully that was before I got my credit card out. I can geek out (Can't spell gEEk without EE...yes that is my job title) with the best of them, but not on that.

[Alpha_Stigma]

Don't get too hung up on the pressure and safety (I say this lightly). A suppressor is never a sealed vessel and doesn't need to be treated as one. Stick to some of the more popular wall thicknesses, ie .065, and you'll be fine. Some have gone so thin as ~.01 (I believe in 316 or 304) and used on a centerfire rifle.

If you haven't already, click on the completed builds thread (link in my sig) and peruse through there. It covers many years of silencer building, both theory and application.

Hey thanks, that's good advice. I was really starting to get in a rut about this actually. 0.065 is easy enough for now.

[ECCO Machine]

Hello, fellow engineer.

1)dont.

PV/T is not a law of physics, its an aproximation. We are dealing with temperatures and pressures WELL outside the scope of that approximation. In adition to that, the fluid dynamics going on dont make the pressure in the blast chamber uniform or calculate-able.

Also, forget modeling fluid dynamics in a silencer. Without a supercomputer and specialized software, you arent even gonna get close.

This.

Even principles like Boyle's law aren't very useful with the extremely short duration and all the variables in play. Coming up with effective designs is an intuitive & iterative process as much as a technical & engineered one.