O ring in closely fitted monocore 22LR can?

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.

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Elkins45
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O ring in closely fitted monocore 22LR can?

Post by Elkins45 » Wed Mar 20, 2013 9:06 pm

First post, so please forgive if I'm in total noob territory here.

I'm thinking of a Form 1 build and have access to a lathe and am planning on picking up a cheap mill (will cost about the same as a factory can) to do the work. I have two questions, one that's design related and a legal one.

1. I'm thinking of a capless design with a seamless titanium tube and an aluminum monocore. The core would be a close friction fit and retained on both ends by screws tapped through the sides of the outer tube. I thought I might groove both ends of the core and seat O rings to complete the seal. My thinking is that not having threaded caps means no threads to crud up, plus less lathe work on the tube. Dumb idea? It's intended for 22LR only (I have a commercial 300 BLK can in process) so it wouldn't need to withstand super high pressures.

2. The tube would be the serialed part. In the case of a baffle strike or other damage, is it legal to destroy the damaged core and machine a new one? The tube would be unchanged and the old part would be sawn into bits before starting the new one, so there would be no 'extra' parts at any time. Any legal problem with this?

TIA for any advice.

DMY
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Re: O ring in closely fitted monocore 22LR can?

Post by DMY » Wed Mar 20, 2013 9:34 pm

First off, once the can is completed, you cannot repair it as per the ATF.

"Persons other than qualified manufacturers may repair silencers, but replacement parts are “silencers” as defined in 18 U.S.C. § 921(a)(24) that must be registered and transferred in accordance with the NFA and GCA."

See here for the full text: http://www.atf.gov/firearms/faq/nationa ... cer-repair

Regarding the friction fit, what exactly do you mean? Would you need a press and some sort of fixture to press the end cap on and off? Or would it be hand-tight?

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Bendersquint
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Re: O ring in closely fitted monocore 22LR can?

Post by Bendersquint » Wed Mar 20, 2013 9:47 pm

DMY is correct, you can't replace any parts only a licensed manufacturer can replace parts.

You destroy your baffle then you have 2 options....File a new Form1 and when approved build a new core, or hire an 07/02 to create your new core.

You can replace a worn out O-ring though. ATF allows that.

Elkins45
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Re: O ring in closely fitted monocore 22LR can?

Post by Elkins45 » Wed Mar 20, 2013 9:55 pm

DMY wrote:First off, once the can is completed, you cannot repair it as per the ATF.

"Persons other than qualified manufacturers may repair silencers, but replacement parts are “silencers” as defined in 18 U.S.C. § 921(a)(24) that must be registered and transferred in accordance with the NFA and GCA."

See here for the full text: http://www.atf.gov/firearms/faq/nationa ... cer-repair

Regarding the friction fit, what exactly do you mean? Would you need a press and some sort of fixture to press the end cap on and off? Or would it be hand-tight?
Thank you for the very definitive answer on the repair question. That is very good to know in advance.

About the end caps: there would be no end caps. The outer tube would be merely a closely fit sleeve slid over the monocore and sealed with O rings around the circumference at both ends.

I will try to draw in Word or by hand and post an image.

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Re: O ring in closely fitted monocore 22LR can?

Post by DMY » Wed Mar 20, 2013 10:24 pm

I think I understand what you're saying now, but I do not know the answer to whether or not that would be acceptable. In theory it sounds good, but I just don't know.

However, I'd be a little worried about getting the tube off after it's been shot. The residue and fouling might make it difficult if it's a tight fit. Threads will at least get the tube moving.

Elkins45
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Re: O ring in closely fitted monocore 22LR can?

Post by Elkins45 » Wed Mar 20, 2013 10:43 pm

DMY wrote:I think I understand what you're saying now, but I do not know the answer to whether or not that would be acceptable. In theory it sounds good, but I just don't know.

However, I'd be a little worried about getting the tube off after it's been shot. The residue and fouling might make it difficult if it's a tight fit. Threads will at least get the tube moving.
I've actually given that some thought. I will probably make a "chamber" with a ledge like the chamber on a rimless pistol barrel. I could "chamber" the silencer and then just tap the core free after removing the retaining screws. The ledge would restrain the tube while the core was free to move forward.

A good smear of anti seize might not be a bad idea either.

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Re: O ring in closely fitted monocore 22LR can?

Post by JohnK454 » Thu Mar 21, 2013 9:47 am

"Cheap mill" is analogous to a "cheap woman" - in my experience, you will dearly regret both. Used Bridgeports or similar are not much more expensive...

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Re: O ring in closely fitted monocore 22LR can?

Post by Elkins45 » Thu Mar 21, 2013 9:49 am

Here's a very poorly drawn diagram done in MS Word:

Image

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MCKNBRD
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Re: O ring in closely fitted monocore 22LR can?

Post by MCKNBRD » Thu Mar 21, 2013 10:28 am

JohnK454 wrote:"Cheap mill" is analogous to a "cheap woman" - in my experience, you will dearly regret both. Used Bridgeports or similar are not much more expensive...
Good lord, bro! Where can you get a used Bridgeport in the $500-750 range?

Elkins45
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Re: O ring in closely fitted monocore 22LR can?

Post by Elkins45 » Thu Mar 21, 2013 10:29 am

I found an image online of someone else's design. I don't like that the tube can only come off in one direction, so my tube wouldn't be stepped on the end.

Image

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Re: O ring in closely fitted monocore 22LR can?

Post by JohnK454 » Thu Mar 21, 2013 3:56 pm

MCKNBRD wrote:
JohnK454 wrote:"Cheap mill" is analogous to a "cheap woman" - in my experience, you will dearly regret both. Used Bridgeports or similar are not much more expensive...
Good lord, bro! Where can you get a used Bridgeport in the $500-750 range?
What I had in mind was a older used Bridgeport (2200lbs) for less than $2000, compared to a chicom (400lb) bench mill for $1300. I made the mistake 25yrs ago of buying one of those cheap bench mills as it was all I could afford at the time and without a doubt it was the worst purchase I have ever made. These days, i have drill presses that are stouter...

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Re: O ring in closely fitted monocore 22LR can?

Post by mollinst » Fri Mar 22, 2013 8:02 am

"Good lord, bro! Where can you get a used Bridgeport in the $500-750 range?"

I bought my Bridgeport series1 from a used machine house in Miami FL for $600 and the cost to ship it to MO was $400 and some change. It was in near perfect condition. You just have to look around - there are dozens of companies that specialize in buying up, rebuilding, and refurbishing machine tools for resale. Inventory changes constantly so, get on their mailing lists and call every month or so... Google is your friend.

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crazyelece
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Re: O ring in closely fitted monocore 22LR can?

Post by crazyelece » Fri Mar 22, 2013 7:45 pm

I see them go in the $500-800 range all the time at auction around here. Of course they are smaller tables without power feed or dros, but still a much better option than the store bought "cheap mill"

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jmorris
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Re: O ring in closely fitted monocore 22LR can?

Post by jmorris » Sat Mar 23, 2013 9:38 pm

Here is another like the above.

Image

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Re: O ring in closely fitted monocore 22LR can?

Post by Historian » Mon Mar 25, 2013 9:41 pm

mollinst wrote:"Good lord, bro! Where can you get a used Bridgeport in the $500-750 range?"

I bought my Bridgeport series1 from a used machine house in Miami FL for $600 and the cost to ship it to MO was $400 and some change. It was in near perfect condition. You just have to look around - there are dozens of companies that specialize in buying up, rebuilding, and refurbishing machine tools for resale. Inventory changes constantly so, get on their mailing lists and call every month or so... Google is your friend.

Bill
Bill, my designer friend was closing shop last year and offered me his Bridgeport for free if I removed it.
After a moment the reality set in. It was the size of the old Snowman coal burning furnaces of the early 1900's and
my 100 year old home had a slight impediment: five foot high under a porch entrance and then a sharp
90° turn through a 3 foot door to three wood steps into the basement. After wiping the mental tears
I thanked him profusely and left as soon as possible to console myself with an ancient single malt.

I had to remember the wisdom of an old WW II US Army Air Corps Engineer: "Sometimes FREE is not free." :)

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Re: O ring in closely fitted monocore 22LR can?

Post by mollinst » Tue Mar 26, 2013 8:48 am

Hell, I'd have put that in my living room if need be! :lol:

Bill
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