A half-assed idea....

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1096369fred
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A half-assed idea....

Post by 1096369fred » Fri Apr 13, 2018 8:06 am

Hey Guys....

Here is an odd idea I had..... I have posted before.... That I really want a AR-15 in 9mm
Upper that uses the MP-5SD system.... I know it is possible.... And machining a 9mm AR barrel,
And porting it to use a SD suppressor would not be that hard.... Just time, skill, and money could make it happen....

But...

What about building an "expansion chamber" that covered
The AR's ported barrel, and allow the use of modular suppressors (THAT YOU ALREADY OWN!) like
My Bower's CAC9 or SWR Trident 9.....

What do ya think..... Would ATF consider it a "barrel extension" or a suppressor itself??? My whole idea
Is to be able to use 115 Gr. Rounds through a ported barrel, that would drop them to sub-sonic volocities.... Like the SD system.... But you know..... In a 9mm AR15!
Thanks!
Fred

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doubloon
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Re: A half-assed idea....

Post by doubloon » Fri Apr 13, 2018 8:48 am

When you say "barrel extension" do you mean it would increase the overall length of the barrel and cover some portion of the detachable suppressor?

A picture would help.
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fishman
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Re: A half-assed idea....

Post by fishman » Fri Apr 13, 2018 8:58 am

It would be considered another silencer so you'd need another stamp but you could definitely do it.

If you're getting another stamp you might as well just get a dedicated integral instead.
That I really want a AR-15 in 9mm
Upper that uses the MP-5SD system.... I know it is possible.... And machining a 9mm AR barrel,
And porting it to use a SD suppressor
Sooo this?
Image

Mines a 45, but they make it in 9. look at the cmmg mkg 9, its the only delayed blowback 9mm AR. The delayed blowback is part of why the mp5sd is so quiet. There's also a guy on here that made a gas operated 9mm upper.
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Re: A half-assed idea....

Post by ECCO Machine » Fri Apr 13, 2018 10:06 am

1096369fred wrote: And machining a 9mm AR barrel,
And porting it to use a SD suppressor would not be that hard.... Just time, skill, and money could make it happen....
That's true of anything, but unless you already have prints, you should make sure you're sitting down when you go over the costs of designing & testing a one-off system like that. The cuts required may not be terribly complicated, but figuring it out and making sure it works is another matter altogether.
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John A.
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Re: A half-assed idea....

Post by John A. » Fri Apr 13, 2018 11:28 am

The way that I have designed my cans, if there is more than one chamber how it is assembled, (ie: reflex/integral) I have always questioned whether the first chamber would suppress the sound of a shot on it's on if nothing else were attached.

If the answer is "yes, it will muffle the sound of a shot", then I refer to the definition of a silencer and consider it a standalone silencer:
The term “Firearm Silencer” or “Firearm Muffler” means any device for silencing, muffling, or diminishing the report of a portable firearm, including any combination of parts, designed or redesigned, and intended for the use in assembling or fabricating a firearm silencer or firearm muffler, or any part intended only for use in such assembly or fabrication.
https://www.atf.gov/firearms/firearms-g ... n-silencer
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Re: A half-assed idea....

Post by doubloon » Fri Apr 13, 2018 2:35 pm

fishman wrote:It would be considered another silencer so you'd need another stamp but you could definitely do it.
...
More or less where I was headed but it was unclear to me how or if he intended to close the path between the "extension" and the detachable suppressor.

Without closing the path it's almost like a giganticus forward venting gas port-ish thing ... except a tube ... that would likely be viewed as a suppressor or suppressor part even if not capped.
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John A.
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Re: A half-assed idea....

Post by John A. » Fri Apr 13, 2018 3:28 pm

doubloon wrote:
fishman wrote:It would be considered another silencer so you'd need another stamp but you could definitely do it.
...
More or less where I was headed but it was unclear to me how or if he intended to close the path between the "extension" and the detachable suppressor.

Without closing the path it's almost like a giganticus forward venting gas port-ish thing ... except a tube ... that would likely be viewed as a suppressor or suppressor part even if not capped.
If not capped, and did nothing to muffle the sound of a shot, that's where I was going.

That to me, would be the same as those sound forwarding muzzlebrakes:

Image
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1096369fred
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Re: A half-assed idea....

Post by 1096369fred » Fri Apr 13, 2018 4:32 pm

Hey Guys.....

I guess I only have a half formed idea of what I am thinking about..... And have yet to put pen to paper.... I guess I'm thinking a tube slightly larger diameter then the suppressor tube, screwed into the barrel bushing, and extending around the ported barrel for a nominal length 6"-8" etc.... With a threaded, open end (think flash can, or maybe the UZI extention for my Trident 9) I guess it would be doable, but only if ATF did not judge it to be a very poorly designed, open ended suppressor.....

Ultimately, it may be easier to adapt a MP-5sd barrel to fit in a 9mm upper.... But as fishman said.... I forgot about the fact that the MP-5 is delayed Blowback.... While most AR-15s in 9mm are straight blow back....but my are they sweetly quiet! It may not really be worth all the hassle..... Easier to screw the suppressor on the end of the barrel stock up on .147s and be happy with what it is..... It just strikes me that there must be some way to slow 115s down to subsonic in an AR platform....

I have been looking for a reason to buy one of those $1800 OMEGA MP-5sd uppers that Atlantic is selling.... Instead of trying to turn an AR into an MP-5.....

Thanks....
Fred

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John A.
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Re: A half-assed idea....

Post by John A. » Fri Apr 13, 2018 8:58 pm

You can build a 2 stage integral can. That's been done for years. And to drop 115's or 124's to subsonic, is also plenty easy with enough ports

The MP5SD barrel uses thirty 2.5mm holes to achieve that. Has nothing to do with the delayed blowback.
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fishman
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Re: A half-assed idea....

Post by fishman » Sat Apr 14, 2018 12:00 am

You can build a 2 stage integral can. That's been done for years. And to drop 115's or 124's to subsonic, is also plenty easy with enough ports
This ^

Make a can that can be used as an integral or with a booster.

The problem with OPs idea is that he wants to add parts to a existing silencer. His idea, even being open ended, would probably still be considered silencer parts. If he made one from scratch or bought a custom can it could work.
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Re: A half-assed idea....

Post by TROOPER » Sun Apr 15, 2018 8:54 am

There's a muzzle device called a 'fire-pig' which is just a cylinder on the end of the barrel. The point of it isn't to reduce overall sound, but to simply direct it away from the shooter. If a standard silencer could be screwed directly onto the end of a 'fire pig', then the 'fire-pig' would become a large blast chamber. It would contribute to the silencer's action without doing anything productive as a stand-alone product.

I don't know if that final statement means anything in a legal sense, because the original 'muzzle-brake' of the MPX didn't do anything productive as a silencer as a stand-alone product, and yet it was declared to be a silencer all the same.

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fishman
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Re: A half-assed idea....

Post by fishman » Sun Apr 15, 2018 11:29 am

the original 'muzzle-brake' of the MPX didn't do anything productive as a silencer as a stand-alone product, and yet it was declared to be a silencer all the same.
This is why I reccomend OP not go through with his plan. All it takes is one atf opinion to shut it down.
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