Beginning build weight question

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milsurpcollector1970
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Beginning build weight question

Post by milsurpcollector1970 »

I got my stamp finally and got the materials
I am building a can for a 45ACP AR rifle. It will also be used for 9mm and 300 BO

I am making a coaxial

Here is what I have so far

https://i.imgur.com/lhRrAXO.jpg

All stainless
The inner tube is .110 thick and weighs 15 oz 1.25 inner dia
The end caps weigh 7oz and 4.6 oz
The outer tube is .089 thick and weighs 14 oz 2 inch outer dia
That’s 40.6 oz with no baffles
Where can I take weight off without it blowing up
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Capt. Link.
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Re: Beginning build weight question

Post by Capt. Link. »

That's massive but curable. It depends on the thread pitch but trimming both tubes to .050 will be more than enough. I would do hoop strength calculations to verify. End caps can be thinned out as well. Non stressed areas of .025-.030 is not uncommon. You may take more out of the tubes using double butting technique where the ends are fat and the majority of the middle is thin. Depending on hoop limits a very thin light tube will result. I'll look for your questions if you have any.
-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!
http://www.silencertalk.com/forum/viewtopic.php?f=10&t=79895
milsurpcollector1970
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Re: Beginning build weight question

Post by milsurpcollector1970 »

Thanks Capt.

I have the inner tubes threaded 28tpi I took the id out to .127 from .125 so I have much to work with.

It’s not Dom tubing more like seamless

Is there a hoop strength formula?

The highest pressure would be 300 BO supersonic
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Capt. Link.
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Re: Beginning build weight question

Post by Capt. Link. »

Burst Calculator www.engineersedge.com/calculators/pipe_bust_calc.htm
https://en.wikipedia.org/wiki/.45_ACP
Image

The outer tube in your plan has no threads so as a pressure vessel it can be thin but leave some meat at both ends for a non deforming gas seal. A rear o-ring can be used but not truly required with a good tight fit.
Engineer the end caps for lightness and stiffness against the compression you will apply to the outer tube in assembly. Take down mechanical points are always nice if you ever wish it to come apart.

:arrow: Always used anti-seize or you will be condemned to hell for all eternity. :evil:

Idea: :idea: Thin the inner tube to .065 wall and thread the outside tube in the areas the inner threads aren't. Allow for stretch and clearance of this inner tube. The outside threads add surface area to the tube for thermal performance and lighten the tube in a simple way. This technique can be used on the inside of the outer tube leaving the ends free of threads for the gas seal. With "lightened" .065 wall I'm sure you will be well within burst limits but you must do the math for all the calibers and tubing sizes for the length of barrels and loads you are using. Be conservative and use a safety factor.

Inner tube: After the vents a internal threaded ring can be used for baffle retention for K or Cone, and use one at the other end to compress the baffle stack.

-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!
http://www.silencertalk.com/forum/viewtopic.php?f=10&t=79895
Historian
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Re: Beginning build weight question

Post by Historian »

" Always used anti-seize or you will be condemned to hell for all eternity. :evil: "


Again HEED the Good Captain's sage & loud clarion call of wisdom and due diligence.

To reenforce this MUST-Do for cans: If you do not your torture in hell
will be to endure for eternity the noxious song and video "CARS FOR KIDS". :)
milsurpcollector1970
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Re: Beginning build weight question

Post by milsurpcollector1970 »

Thanks for the links and info

I’m a little confused as to how to use the formula

The psi from a 45 acp is going to be different at the muzzle, vs inside the case when fired. How do I determine that number?

I have several different kinds on anti seize is one better for cans
I have automotive and moly barrel paste
Historian
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Re: Beginning build weight question

Post by Historian »

milsurpcollector1970 wrote: Thu Apr 07, 2022 5:52 pm Thanks for the links and info

I’m a little confused as to how to use the formula
The psi from a 45 acp is going to be different at the muzzle, vs inside the case
when fired. How do I determine that number?
Referring to "Silencers Principles 1968", US Gov. R-1896, p.117
on .45 test:

They gave muzzle pressure ~1,600 psi.
Volume of .45 barrel is (½ x .45)^2 x Pi.
Multiple together for PV value aprox. 1,272 .
At top limit based on a Don Walsh's great
can long ago with dimensions 1.75" diameter and ~ 9" length
get a useable volume with baffles of ~ 18+ cubic inches.
Rough division gives peak can pressure at about 600psi.

Trust But Verify. :) :)

p.s., when .22 fired in Walsh's can .... "That was not a BB gun You Heard" -PTK
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Capt. Link.
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Re: Beginning build weight question

Post by Capt. Link. »

Only use high temperature anti-seize ,its normally silver or copper colored. Molly bore paste is not what you want to use.

Use this for the muzzle pressure formula http://closefocusresearch.com/calculati ... n-systems

-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!
http://www.silencertalk.com/forum/viewtopic.php?f=10&t=79895
Historian
Silent But Deadly
Posts: 3503
Joined: Mon Mar 29, 2010 10:37 pm

Re: Beginning build weight question

Post by Historian »

Historian wrote: Fri Apr 08, 2022 10:56 am
milsurpcollector1970 wrote: Thu Apr 07, 2022 5:52 pm Thanks for the links and info

I’m a little confused as to how to use the formula
The psi from a 45 acp is going to be different at the muzzle, vs inside the case
when fired. How do I determine that number?
Referring to "Silencers Principles 1968", US Gov. R-1896, p.117
on .45 test:

They gave muzzle pressure ~1,600 psi.
Volume of .45 barrel is (½ x .45)^2 x Pi.
Multiple together for PV value aprox. 1,272 .
At top limit based on a Don Walsh's great
can long ago with dimensions 1.75" diameter and ~ 9" length
get a useable volume with baffles of ~ 18+ cubic inches.
Rough division gives peak in this can pressure at about 70psi.

Trust But Verify. :) :)

p.s., when .22 fired in Walsh's can .... "That was not a BB gun You Heard" -PTK
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