Barrel shrouds and dead air space

[mcoulter]

Howdy all,

I have a Brocock Sniper HP in .22 and have been looking more closely at the shroud and end cap.  I have read of folks using hair curlers wrapped with felt in this dead air space to further quiet the perceived sound when firing the gun. Then I start wondering why the manufacturer didn't do this... 

Here's a pic showing the approximate amount of space in this area of my gun:



I have also read of folks who try to vent this area back into the shroud by drilling holes in the barrel collar and then more holes in the back end of the shroud.  Then I start thinking that the manufacturer is probably way smarter than I am, so there's probably a reason why the gun is the way it is...   

The gun is reasonably quiet with the shroud - but if I can make it *a little* more quiet without affecting accuracy, that would be a goal to work towards.  Likewise, it would *seem* like the blast of air exiting the muzzle only to be trapped in this dead air space would affect accuracy.  Note, this is a decently powered .22.  It's shooting JSB Monsters at about 890 fps (45 fpe) so there's quite a blast occurring here.   Yes, I have shot it without the end cap and without the shroud and it's REALLY LOUD!  It is pretty remarkable just how much the design quiets the gun down.

Anywho, I would love to hear from folks who have some experience playing with similar barrel shrouds.

[Nomadic Pirate]

That dead space isn't really dead, it does trap quite a bit of noise, try shooting without endcap and check the difference.

My suggestion ( if don't want to make the gun much longer is to get a Reflexed LDC from Neil Clague, maybe only 4" in front but with the longest reflex you can get, that's the lenght from the end of the shroud to the end of the air tube.

[Nvreloader]

Matt

Some Questions,
What is the diameter of the alum part of the barrel collar?
What is the diameter of the bbl?
What does the "O" ring do, (on the bbl), is there another one on the other side?
What is the distance from the front of the bbl collar to back face of the barrel end cap?
What is the distance from the end of the muzzle to the front of the action where the shroud attaches?

Thanks,
Don

[HunterWhite]

The Hatsan Flash comes with something that's called "hair curlers" but they are designed for the purpose of reducing noise.

I will include a picture of Flash baffels.

The empty chamber is called an expansion chamber, these were very common on old dirt bikes. They reduced the sound of the ring dings somewhat. Expansion chambers do work.

The pressure in the barrel is high, maybe 1500 PSI. When the pellet exits the barrel it's like popping a champagne cork.
If it pops into a chamber equal to barrel volume it will have a pressure of 750 PSI, so less report.
If the volume of the expansion chamber is triple the volume of the barrel, then the total volume is now 4 times the original barrel volume, so 375 PSI.

A series of baffels will do the same thing. Each little chamber dosen't work as well as the large one that you have,  but there are many.

The plastic thing in the top of the photo is 3d printed, it's an after market item, or home brew.
The stock Hatsan "hair curlers" are below with two little expansion chambers. The white squares wrap around the " hair curlers"

Here is a link if you're interested.

https://www.google.com/search?client=ms-android-tmus-us-revc&q=Hatsan+QE+baffles&sa=X&ved=2ahUKEwivgdDv46zqAhUQ-6wKHQfCC18Q1QIwBnoECA0QAg&biw=360&bih=668#imgrc=Zp6_Ku-EpoqRuM


Hunter

[Ribbonstone]

If that is a useable thread ahead of the end cap...then you are set up for a good experiment.

1. As-is.
2. As is with a short LDC screwed onto the end cap thread ..."they"can make short extention LDC's  if you ask).  Can always sell the shorty LDC to not lose too much $.
3. LDC unscrewed and the rear bushing vented for back flow.Can always plug the vents if it turnes out worse.
4. I'd likely,depending on how easy the the shroud's ID to limit machine work,make ONE baffle beteen the muzzle and the end cap and toss it into the experimental mix....could easily be taken back out.

Quit bets:
#2 could amke it a couple of inches longer (depending on how stubby the add on LDC is)....but am betting that option would be most quiet.

#4 would be real close.

#3 in a distant  3rd place but a little better than #`1.

[mcoulter]

Thanks for all of the quick responses on this  :-)

 - Manny, yes, I have fired the gun without the end cap (only) and without the end cap AND shroud - I can confirm that it's loud in both instances.  So the shroud here IS quite effective!  This is unlike a Kral I had which had a shroud, but the end cap was directly connected with the muzzle so there was NO dead are space there.  The shroud did NOTHING in that case.

 - NVreloader, here are the measurements:

What is the diameter of the alum part of the barrel collar?
24.74mm  (this measurement is of the metal only, it does not include the o-ring)

What is the diameter of the bbl?
13.50 mm from muzzle to collar and then 14mm in between collar and the receiver.

What does the "O" ring do, (on the bbl), is there another one on the other side?
It's a mystery.  I have no ideas what the oring does.  It feels epoxied to the barrel.  It mates with nothing.  There is not an oring on the back side.

What is the distance from the front of the bbl collar to back face of the barrel end cap?
I estimate this at 96.5mm.  I measured the distance from the front of the collar to the end of the shroud at 109mm and then subtracted the thread depth of the end cap (12.5mm).

What is the distance from the end of the muzzle to the front of the action where the shroud attaches?
It is 19.5 in to the very end of the threads at the receiver side.  The beginning of the threads measures 18.5 in.

 - HunterWhite, thanks for explanation of how the volume of space works with the collection of air exiting the barrel and the pics of the hatsan and after market items.  That's pretty much what I was thinking of.   Adding the hair curlers and felt would be an easy (non-destructive) thing to test.  But these items would take up that volume and might negate the quieting perhaps?

 - Ribbonstone, yes, that's standard 1/2 UNF thread.  I had a moderator on the gun but I think some clipped pellets caused this which is the other part of question which I have not brought up here yet...   





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And a few more pics:

[Nomadic Pirate]

I agree on the point that aircurlers will basically only take up space,....I'm prepared to bet that the curlers and felt adding will be negated by the loss of space, and you'll hear no difference after all.

[HunterWhite]

I tried the Flash several ways.
The 22 cal flash is 30 FPE.

As supplied, not as quiet as M-Rod 25 at 40 FPE, but close.

With everything removed and no end cap, kind of loud, but not 22LR loud.

 With the curlers removed, end cap in place, not as quiet as with curlers installed.

Those curlers do something.

Hunter

[KnifeMaker]

Yes they do Hunter. The most successful ldc that has been in thousands of pcp's is the British versions and they have they have the hair curlers in them. Very quiet!


One example is the ldc than comes on the HW 100. Very effective.


However, for higher power AG's I make the hair curlers out of alu. tube and vent it.   


Manny said that it wouldn't work. However, this is exactly how his favorite ldc's from N.C. are made inside. LOL



Mike

[AlanMcD]

The "hair curlers" and baffles work by disrupting the pressure pulse and thus the sound waves.  Shrouds and LDCs reduce sound through both controlled expansion of the air charge (the pressure drop described before) and disrupting the pressure pulse.  The disruption of the pulse is extremely important, and that is why we are better off giving up some volume for the "hair curlers" and baffles.

[Lani52]

What Knife says.

I use 1.5 hair curlers, wrapped in felt in a 45 FPE 22.  They are contained in a piece of tubing that slides inside the shroud and has vented fiat fender washers to compartmentalize and further slow the air down.  The curlers replaced aluminum cone baffles that were inefficient.  The system also utilizes a air stripper to divert air back into the rear of the shroud. 

Regards,

Roachcreek

[Pelletjunkie]

I like the clean lines of a shrouded gun so I redesign all the shrouds on my guns to be internally silenced. I might have to add an inch or two but it beats adding a 5” can. I can’t stand making a short gun long or a longer gun look like a goose gun so I just put in the effort machining different components until I found a combo that works quite well. Manufacturers can do it, Taipan does, SPA tried, but I think it would just add more cost to already overpriced guns. I would post some pics but it’s an aggravating experience on this forum.

[Mr.P]

I was noticing some things about the space inside of the shroud of my talon p. that relate to some of the discussion here.

Front barrel bushings are perforated Allowing air to flow back into the space between the barrel and the outside of the gun. I took out the barrel to do some cleaning and this whole space was filled with lead dust so it’s obvious there’s a lot of air expansion and flow going on in this chamber.

I also wonder if anything can be done with the space to deaden the gun a little more, or if it is already doing the best it can.  I could definitely stuff some felt in there if it would dampen the sound.

[Nomadic Pirate]

Yes of course curlers baffles work but we are talking about this specific situation,...not in general.
You need length and or with for it to work,..in a situation like in that of the OP rifle there's so very little room that I bet you'll see no difference.

Fill those 2" with curlers and felt and then let me know what kind of a real difference it made 

[rkr]

Yes they do Hunter. The most successful ldc that has been in thousands of pcp's is the British versions and they have they have the hair curlers in them. Very quiet!


One example is the ldc than comes on the HW 100. Very effective.


However, for higher power AG's I make the hair curlers out of alu. tube and vent it.   


Manny said that it wouldn't work. However, this is exactly how his favorite ldc's from N.C. are made inside. LOL



Mike

Listen to Mike, he knows what he's talking about. I've modified built and measured dozens of different silencer combos and felt always adds some extra silencing effect. There are good designs that meet or exceed commercial silencers without felt but when you add felt to them they become even more silent. Hair curlers are meant for 12 fpe guns and they start breaking up when you increase the power necessitating perforated aluminium or steel tubes in high power guns.

In this case I would start by backventing the shroud, loads of small holes (as big as fits) to the centering collar and one baffle 15mm in front of the muzzle - leave that chamber empty so air can actually get in to the shroud without curler and felt blocking it. On front of that HW style 3 chamber system with aluminium curlers and baffles. If 3 chambers gets too long try 2 chambers. That setup won't be quiet but it will be much more quiet than your current shroud. Add a short and stubby silencer on front and the noise level should be bearable. I would also consider shortening or hollowing out that endcap.

[Pelletjunkie]

I have more time now so I will try to elaborate my experience with shrouds and post some pics. Hopefully they won’t be upside down or sideways. To the OP, your shroud is almost worthless until you vent that barrel collar, I think that’s what you called it. Your gun may actually shoot better. Right now, with that thing sealing off the shroud, you have quite a high pressure area going on. Now for the curler debate. They work fine but you have make life easier on them by stripping as much air as possible and venting it back your shroud. My Priest is or was shooting 34gr slugs at 930fps. It’s not a Condor shooting a buffalo bullet but it’s on par with most guns that are not going to be gentle on silencing stuff. As far as venting your shroud goes, one little hole will do. The hole or holes you drill in your shroud have an effect on sound, but not at the muzzle. Three tiny holes can emit a higher pitch sound than one hole but that also depends on the gun and how much air you are pushing. It is also only really noticeable to the guy behind the trigger. That’s why some felt in the back of the shroud is nice. It also helps with lead dust. Just remember if you vent your shroud, do it opposite side of your face. Shroud material and your silencing material also has a big influence on how your gun sounds. Initially I was using aluminum tubes and machining all my components out of aluminum. One day I made an experimental setup out of delrin and hair curlers. Didn’t want to waste aluminum if it didn’t work. Well it worked so I built everything out of aluminum. It was beautiful but my gun was louder. So now I use delrin and CF everywhere I can. In the first pic, hopefully, will be generally what I use in my shrouds. I am stripping as much air as I can with that first baffle and sending it back the length of my shroud. I put it about one inch from the crown of the barrel. That first baffle is also pinned to the shroud because it is going to take a beating. You can see the button head securing it if you look closely at the underside of the shroud on my Orion bullpup. The other pic is 3 of my guns, all quiet, all short, and no junk hanging on the end of them.

[Pelletjunkie]

Old sparky, I hope this helps. PM me again if you have any more questions. Right now I am building a quiet shroud for a Kral Jumbo project.

[mcoulter]

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  :-)

[Pelletjunkie]

If you look at the first pic, you will see how I machined the cone baffle, the chamber spacer and the end cap so the curlers lock into them. Knife mentioned to me in a conversation over on AGN that guys crush those curlers when they shade tree the job. You have to keep the air from pounding them into accordions. Here is another pic, hopefully, of my Priest shroud. That button head is securing that first cone baffle. If you don’t , you will pound everything in front of it into submission. If you don’t want to go my route you could try a baffle stack with a spring like the Marauder uses. You will have to use a longer or larger diameter spring that clears your barrel and rests on that collar. Just food for thought if you are leery of taking a drill to your shroud.

[Pelletjunkie]

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.