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All Springer/NP/PCP Air Gun Discussion General => Machine Shop Talk & AG Parts Machining => Topic started by: lloyd-ss on May 10, 2011, 08:39:02 PM

Title: Anybody tried stuffing the back end of a shroud (PICS ADDED)
Post by: lloyd-ss on May 10, 2011, 08:39:02 PM

Has anyone tried stuffing the big empty cavity of a full shroud?  I've got a nice air stripper at the muzzle to send the bulk of the air to the rear, but I feel that some sort of non-packing sound absorbing materials to kill the back pressure wave could make a big difference.

Three different rifle set-ups

.688 barrel O.D. with 1.090 shroud I.D.  (.510 cal)

.625 barrel O.D. with 1.150 shroud I.D.  (9mm)

.562 barrel O.D. with .900 shroud I.D.   (.357)

Any thoughts on this or suggest a good material?  

Thanks,
Lloyd

Title: Re: Anybody tried stuffing the back end of a shroud
Post by: SDale on May 10, 2011, 09:30:48 PM

Cheap Scotchbrite pads work fairly well!  ;D

Title: Re: Anybody tried stuffing the back end of a shroud
Post by: kro77 on May 10, 2011, 09:44:06 PM

I used the white sanding pads from 3m. I believe 00 equvalant and cut them down the middle to thin it out and cut to the diameter needed.  It settled things down very much.

Title: Re: Anybody tried stuffing the back end of a shroud
Post by: goodland on May 10, 2011, 10:05:08 PM

Mr clean magic eraser made of pure melamine very good sound absorber

Title: Re: Anybody tried stuffing the back end of a shroud
Post by: lloyd-ss on May 10, 2011, 10:57:35 PM

Thanks guys.  I think they have that sort of thing for cheap at the local Big Lots. 

Nobody mentioned fiberglass.  I guess it packs too much , and also  blows little fibers around?

Lloyd

Title: Re: Anybody tried stuffing the back end of a shroud
Post by: lloyd-ss on May 11, 2011, 02:57:58 AM

Here are some pics of the shroud.  It's a big thing with a 32" long  barrel, .510 cal.  33" of the shroud sticks out from the receiver.  End cap and receiver adapter are threaded into the shroud tube which is 1.25 O.D. with .08 wall.  Very stout.  No blowing the end cap out of this one. The air stripper threaded onto the end of the muzzle has big openings to send the bulk of the excess air back toward the receiver.  I want to stuff that section with some sound absorbing material.  At the muzzle are several "decorative steel washers," to redirect the residual air and take away some of the energy.

I hope to get a video sometime soon of this thing in action.

Thanks,
Lloyd


(http://i226.photobucket.com/albums/dd79/loyd500/510shroud/510shroud-1.jpg)


(http://i226.photobucket.com/albums/dd79/loyd500/510shroud/510shroud-2.jpg)


(http://i226.photobucket.com/albums/dd79/loyd500/510shroud/510shroud-3.jpg)


(http://i226.photobucket.com/albums/dd79/loyd500/510shroud/510shroud-4.jpg)


(http://i226.photobucket.com/albums/dd79/loyd500/510shroud/510shroud-5.jpg)


(http://i226.photobucket.com/albums/dd79/loyd500/510shroud/510shroud-6.jpg)


(http://i226.photobucket.com/albums/dd79/loyd500/510shroud/510shroud-7.jpg)

Title: Re: Anybody tried stuffing the back end of a shroud (PICS ADDED)
Post by: Bullit on May 11, 2011, 12:24:33 PM

Lloyd do you space the washers?  Do you pack between them w/the Scotchbrite material?

Title: Re: Anybody tried stuffing the back end of a shroud (PICS ADDED)
Post by: lloyd-ss on May 11, 2011, 02:06:52 PM

I don't have them in the picture, but I use a short piece (about .25 long ) of tubing between each washer to space them.  I had to expand the O.D. of the washers to make them a force fit into the tube, then a tube spacer between each washer.  After its all threaded together I force a .560 madrel thru the washers to do a final centering and sizing.  Honestly, I haven't found anything that will stay put in the front end between the washers in the big-bore sizes, and that has led to a few..... uh, mishaps.    :-[   Those metal washers take a pretty severe hit from the air blast.
Lloyd