Barrel shrouds and dead air space

[mcoulter]

Oh, once again, you must drill a couple holes in that collar. I would have done it the day I bought the gun unless it was a low power .177. You might as well not have a shroud on the gun. Not sure why they went that route. That foster nipple looking stripper on your end cap is about perfect for centering a felt wrapped baffle.

Without the shroud the Brocock is VERY similar in loudness to a Kral Big Max.  That gun's barrel shroud was entirely useless.  To my ear both are darn close to a standard velocity 22lr.   In other words most definitely NOT backyard friendly.  The Kral NEEDED a LDC and the Rocker1 I had did make the Kral entirely backyard friendly.  To my ear, the Brocock WITH the shroud (as imperfect as it may be) does make the gun much more backyard friendly.  Keep in mind that while both are .22 cal, the Brocock is shooting about 6fpe hotter than the Kral ever did. 

Like you, I really don't like the looks (or in my case the attention) that an air gun's ldc may bring.  My goal is to bring down the bark just a bit while keeping the gun its original length (about 40 inches).  FWIW, before the Rocker1 became damaged, it did GREATLY reduce the sound of the Brocock.  With it, the gun truly only made a "pffffttt" when shot!

 

[JohnnyPDX]

I have a small contribution to this topic.

1) Instead of felt you can use canine potty training pads with the plastic layer removed. It allows for more precise control in making the haircurler fit in the tube centered.

I drilled the forward collar in my TalonSS and it helped a bit, no harm done anyways. It seems that the back barrel collar needs at least on hole to let the air escape from the back of the gun. Both my old AirArms shrouds had one hole at the back end of their shrouds. In the Talon the rear collar rests quite snugly against the power wheel and I belive gas can pass throught eh center of the power wheel exit in the PW adjustment window.

[AKM]

The shroud works the same a "expansion chamber" in the LDC.
Most LDC designs require an expansion chamber first to lower the pressure a bit before it hits the baffles or sound deadening material.
The shroud allows for more baffles or sound material to be used inside the LDC to keep the length as short as possible.

[rkr]

Wow!  Thanks for ALL of the collective wisdom shared here!    So based on comments here it sounds like:

• Felt (or similar material) is a worthwhile addition.
• Given the power of my gun, 45fpe, plastic hair curlers should be OK.
• Allowing the venting of air backward through the shroud helps. (This may be a phase II or III since I want to test non-destructive methods first.)

I'll see what I can put together and report back  :-)

I have seen plastic curlers is a HW silencer come apart at 45 fpe and they are tough ones. I would go for perforated aluminium tube. You can get perforated aluminium sheet from the bling-bling section of your local automotive store, wrap rolls out of that and secure with some wire.

[Lani52]

I found that at 45 FPE, one or more hair curler contained in a identical length tubing with a baffle made of a perforated  fender washer on each end works fine if a air stripper is used as in my Diana Skyhawk/p-15.  For the baffle in the air stripper to replace the poorly made cone baffle I used another fender washer but not perforated.  I have perhaps 2 to 3 thousand pellets thru it in the past Year.

However when I tried hair curlers inserts in the 200 FPE Texan LSS, all bets were off. The torrent of air surging through end unit on the LSS shroud with cup baffles collapsed both plastic  and brass constructed hair curlers. 

I ended up making a spool with one end removed, from perforated stainless tubing, remaining end of the spool was made from a 2 inch fender washer turned to fit inside the large cup baffles, the perferated stainless tube was attached to the drilled out to fit fender washer with JB Weld, then the perforated spool was wrapped in felt and inserted inside the cup baffles.  This made a noticeable difference and has held up so far. And again this was used in conjunction with a air stripper in the shroud. The weak point now is the strength of the J B Weld.

Roachcreek

[old sparky]

This is cool stuff. Thank you for posting the pictures. I have a Air Arms that is loud! and as long as a goose gun. I may get it out and look into this stuff.

thanks,

[KnifeMaker]

A couple of years ago, Earnest of Fx Fame posted  that he replaced the felt with memory foam and it gave a deeper and less offensive sound. i found it odd as Memory foam has no open pores large enough to do much. However, I tried it and yep, it worked!


Knife/Mike

[KnifeMaker]

Perhaps Manny should try things before proclaiming that it can not work. Especially as so many have found that it does indeed work. 

[mcoulter]

Well I was hoping to have something to report back on after a nice, long holiday weekend, but this happened (be sure to turn up your volume):

[rkr]

A couple of years ago, Earnest of Fx Fame posted  that he replaced the felt with memory foam and it gave a deeper and less offensive sound. i found it odd as Memory foam has no open pores large enough to do much. However, I tried it and yep, it worked!


Knife/Mike

I tried neoprene which has rather similar properties and it was worse than felt as measured. It could be that memory foam compresses more making it better. The best way to lower the dB peak frequency is to increase the outlet size on the cap of the silencer. I've measured 6mm vs. 9mm hole and the peak stays the same while moving few thousand hertz down in frequenzy band.

[rkr]

Perhaps Manny should try things before proclaiming that it can not work. Especially as so many have found that it does indeed work. 

It's too much work when you just happen to know these things

[Nomadic Pirate]

Perhaps Manny should try things before proclaiming that it can not work. Especially as so many have found that it does indeed work. 

What are you talking about,......maybe read before you just spew,

I never said it doesn't work, but you need space and volume for it to be effective, to just ad it to a little 2" space it will not do much opf a noticeble difference,

Since you mention Neil Clauge uses thatr method, once I asked to make me a 4" LDC and that is exactly what he said,


You are just salty since I don't believe in your other values LOL ....but you need to read LOL

[Nomadic Pirate]

The shroud works the same a "expansion chamber" in the LDC.
Most LDC designs require an expansion chamber first to lower the pressure a bit before it hits the baffles or sound deadening material.
The shroud allows for more baffles or sound material to be used inside the LDC to keep the length as short as possible.

Quite right my man

precisely my suggestion on my first post, use those 2" as an expansion chamber then ad a short, reflexed Neil Clauge LDC if you want to keep the gun relatively short.

[rkr]

The shroud works the same a "expansion chamber" in the LDC.
Most LDC designs require an expansion chamber first to lower the pressure a bit before it hits the baffles or sound deadening material.
The shroud allows for more baffles or sound material to be used inside the LDC to keep the length as short as possible.

Quite right my man

precisely my suggestion on my first post, use those 2" as an expansion chamber then ad a short, reflexed Neil Clauge LDC if you want to keep the gun relatively short.

Without backventing the shroud that would be wasteful. Backventing the shroud will give you the same effect if not more as all the dead space in between the barrel and the shroud will be your extension chamber. This allows that 1.5" space that's left in the shroud to be used as the first chamber of your silencing setup giving you much more quiet gun. Of course if length doesn't matter just stick A&M Marksman on front of the shroud and it will be really quiet.

[KnifeMaker]

Your beating a dead horse Ric. Surprised Manny threw politics into a post yet again. I would have thought he would have learned better than the dig's by now.


Knife

[Lani52]

Can we just get back to the nipple idea?

I tried super glueing it on and it came off and pulled hair off my chest.

Would JBWeld or gorilla tape work better?

Regards,

Roachcreek

[Nomadic Pirate]

The shroud works the same a "expansion chamber" in the LDC.
Most LDC designs require an expansion chamber first to lower the pressure a bit before it hits the baffles or sound deadening material.
The shroud allows for more baffles or sound material to be used inside the LDC to keep the length as short as possible.

Quite right my man

precisely my suggestion on my first post, use those 2" as an expansion chamber then ad a short, reflexed Neil Clauge LDC if you want to keep the gun relatively short.

Without backventing the shroud that would be wasteful. Backventing the shroud will give you the same effect if not more as all the dead space in between the barrel and the shroud will be your extension chamber. This allows that 1.5" space that's left in the shroud to be used as the first chamber of your silencing setup giving you much more quiet gun. Of course if length doesn't matter just stick A&M Marksman on front of the shroud and it will be really quiet.

Well Yeaahhh, backventing the shroud will only help more, now you have you 2" empty expansion chamber and an immediate extra area behind do push some air,....every little bit helps, Will Piatt used to stuff green dish cleaning felt strips in the back vented shroud, I've been using those white Mr Clean sponges after watching Hajimoto doing it on his Air Speed.

[superchikn]

Can we just get back to the nipple idea?

I tried super glueing it on and it came off and pulled hair off my chest.

Would JBWeld or gorilla tape work better?

Regards,

Roachcreek

Not sure,  may try one or the other and see.