I've been thinking about this one for a while.  I have a crappy Mossberg 500 20-ga that I picked up used, and I'm looking to make it quieter.  I understand that only limited suppression is possible with shotguns.

I've seen pictures of the integrally suppressed Mossberg barrels that Hushpower sells over in the UK.  Some of the videos of these things suggest that a pretty big reduction in sound is possible.  However, we can't get them here.
http://www.saddleryandgunroom.co.uk/Gunroom/SG_Hushpower.htm


While there are no pictures (that I can find) of the Hushpower internals, this thread suggested that the overall design of a shotgun suppressor could be pretty simple:
http://www.silencertalk.com/forum/viewtopic.php?f=10&t=61025&start=25.  It sounds like this guy was able to get pretty good suppression using his design, but I don't like the use of packing material inside the suppressor.  Especially since the ATF ruled that Brillo pads are considered suppressors:  http://www.wnd.com/2011/11/368769/



I've been thinking about a fairly simple design for a ported-barrel type 20-ga suppressor.  Because there are no long barrels available for the 20-ga 500, I've incorporated a barrel extension into the design so that there is enough length for porting.  This is similar to what the Hushpower supposedly does.  The design uses a 24-inch barrel that has had the rib removed, and been turned to a uniform OD past the magazine tube cap.  The last 2 inches would be hacked off so the removable choke wouldn't be a problem.

A 2.5 inch OD aluminum tube with .125" wall would form the main body of the suppressor.  10 baffles would either be welded or silver-soldered to the barrel and extension, and be turned down after fixing to fit neatly into the tube with some clearance.  The rear cap for the tube would be silver-soldered or welded to the barrel, and have 1 or two O-rings to seal against the tube.  

The barrel extension would either thread on or slip over the front of the barrel (haven't decided) and then be soldered or welded.  The front tube cap would be pressed into the tube and have one or two O-rings to seal against the barrel extension.  The end of the barrel extension would be threaded so that a nut would bear against the front tube cap and hold the whole assembly together.  If removed, it would allow the tube and front cap to be slid off of the baffles for cleaning (last pic).












I would welcome any ideas or comments on the design.  In particular, it would be a pain to bore the barrel extension to the right ID (0.615") over its whole 13-inch length.  There's probably a better way to do this.  Anybody make a super long Mossberg 500 20-ga barrel?    


Finally, I have some specific questions regarding a Form 1 build of this thing:
1.  On a form 1, is the total length of the integrally suppressed barrel considered the silencer length, or do I just consider the tube length?
2.  Does the fact that the suppressor assembly could be disassembled into 2 pieces for cleaning cause any problems for me with the ATF?

That's an ambitious project, I look forward to following it.  The only shotgun suppressors I've seen are huge and aren't all that quiet.

I'm not sure I follow the drawings, but as long as the barrel and anything permanently attached to the muzzle end are 16"+ inches, I don't see how it's any different than a short rifle barrel with a permanently pinned muzzle device.

Or you could pay for an Short Barrel Shotgun stamp.

The assembly should always be long enough- I just thought there might be some issue with a suppressor that breaks down into multiple pieces, because the ATF considers each piece to be a suppressor in and of itself.  I'm not sure how this works right now with take-down .22 cans.

Have you looked @ the greatly extended Hastings shotgun tubes & loading subsonic ammo?

The trick is you have to use subsonic loads or start porting very close to the chamber to bleed off enough gas to get standard loads to stay subsonic (starting in the first 8" of barrel). I used a single shot 20ga so I could start the porting early and use standard loads. I also made some m baffles with a tapered bore so they act as chokes to keep the wad closed but are otherwise traditional baffles.



http://youtu.be/38xI-AooT_w

Very clever.

bjgunner- I saw your work while I was researching my design- nice job .  What did you use to determine the o'all length for your suppressor on the Form 1 (assembly or just the tube)?

I will probably start reloading subsonic loads once I get this thing all squared away- I'd like to be able to keep the pump action.

The registered length is the suppressor tube on mine. I'll probably end up doing a pump in the future and load subs but I'll just do a longer stack of the tapered baffles instead of the perforated barrel.  The tapered bore keeps the wad closed perfectly, the spacing of baffles is the most important part though. I built it so the wad is entering a baffle as it the exiting the one before so it's always supported

I was at the range this past weekend and one of the guys had me shoot his over/under 12 Ga through my chrono.
He was using these 12 Ga "shorty" slugs. I'd never seen or heard of them before. Instead of the normal 2-3/4" long
12 Ga. shells, these were maybe 1-1/2" long and had a flat nose slug in them.

In this guy's over/under (20" or so barrel I'd guess) the two shots registered 1003 fps and 985 fps. You could hear the
slugs whistling down the range. It would have been awesome suppressed.

They were factory loads. The old guys were sniffing the spent hull and were in agreement that it had been loaded with
Red Dot.... LOL.

-ZA

This is relevant to my interests.  

I have several shotguns in the closet collecting dust and a propensity to submit random form 1's.

This is the "Meineke" suppressor from earlier in the thread:  https://www.youtube.com/watch?NR=1&v=dnX7p5Atu5A

Tag for later for when I'm not at work. I've been researching on doing this but with a 410 version. Easier to supress. Glad to know I'm not the only crazy bastard in the states that wants to do this

Extra baffles.  Say you have a .22" can that has 10 baffles.  You take it apart to clean it, you've got 10 baffles rattling around your shop.  You can't have an 11th baffle, b/c that would be a part for a 2nd suppressor you don't have a stamp for.

I did a 410 version first (thinking it would be easier). It was actually more of a pain since the wads are so thin. The 20 gauge is easy to work with since the standard wad is robust.

Integral bolt action 410 above a standard bolt action 410

How's it sound?

Very cool shotguns.  My 20 Gauge F1 should be back in the next couple of months (hopefully) since it has been pending since January.

My ambitious plans are to attempt to make a suppressed 20G O/U with an oval tube over both barrels.  I was planning on just porting the barrel the whole way (no baffles) and using screen or stainless chore-boy inside the tube to slow the gas down and keep the shot subsonic.  

Hopefully I can get enough suppression to make it hearing safe with just aggressive porting over a 28" barreled 20G Yildiz and not have to make any baffles.

The ATF ruling on that stuff has really made "disposable" packing a non-starter for suppressors.

I am usually a stickler for following the letter of the law.  

However, if it ever came to the point where you needed to replace the screen or packing material in a suppressor  I think folks who own suppressors that use that type of material  that are probably pretty safe to ignore a tech branch letter which was not addressed to them and whom are not dumb enough to ask for their own.  I certainly doubt the ATF is going to arrest somebody because they have a suppressor utilizing screen or packing material and they also have screens on the window of their house and which now potentially represent unregulated suppressor parts any more than they were going to arrest somebody for owning a mini-14 and shoelaces.

Ultimately, if you really worried about it  and 10 years from now and you had to replace the screen or packing material,  you could bring spare a framed screen window from home depot to a local C2 and say can you swap this out for me and dispose of the old screen for not a lot of cost.

You could also just register a 6" diameter, 4ft long piece of PVC tube and fill it full of extra screen material.    That way you could always have extra material as there is no letter stating you cant move baffle material from one suppressor to the other.

I guess my point is I am not going to have my design be shaped by somebody else's idiotic letter and what I may do about replacing the screen material a decade or more from now if it ever wears out.

Also, the recent muzzle break =/= a suppressor ruling would be a precedent in your favor.

 

Not really interested in owning one myself- but I LOVE watching others' follow their ideas through from concept to completion! Looks good OP and can't wait to see you get started on this some day!

suppressed double barrel?!

https://www.youtube.com/watch?v=UUTq8rjNZ3Y