Holes in a shroud

[aldea6]

Hi, I noticed that many shooters , who have a shrouded barrel , drill a row of some tiny holes in the shroud to decrease the air pressure exiting the barrel and so reducing the noise.I wonder if it's more efficient to drill the holes at the rear of the shroud , just after the receiver , or at the muzzle end before the baffling system? Also what diameter to drill ?

Mike

 

[Vetmx]

I always drill the rear of my shroud with 3 holes. I never let the diameter of all 3 holes added together exceed my caliber. I also wrap some felt around the back of my barrel so I don’t get dusted. 

 

[SilentSquirrel]

Does drilling the holes quiet the gun at all?

What are the other advantages & also the disadvantages of doing it?



Thank

Ed

 

[shambozzie]

This is the shroud on my cricket compact. Unscrewed for photo. Holes are top and bottom. Thanks Ernest Rowe.

 

[Long_Gun_Dallas]

My 380mm fx crown barrel came with one drilled at the back. I've never needed to do it on another gun, but could see the benefit. 

 

[bucketboy]

There are a couple of things the hole can do...reduce internal pressure...change to tone of the muzzle report ...improve accuracy.



Hole in the rear vent air out giving a deeper tone, holes just forwards of the muzzle jet the air out sideways stabilising the barrel (just like a muzzle flip compensator), hole near the front seem to me to of no benefit.



Bb

 

[aldea6]

That makes sense to me, bucketboy

 

[SilentSquirrel]

There are a couple of things the hole can do...reduce internal pressure...change to tone of the muzzle report ...improve accuracy.



Hole in the rear vent air out giving a deeper tone, holes just forwards of the muzzle jet the air out sideways stabilising the barrel (just like a muzzle flip compensator), hole near the front seem to me to of no benefit.



Bb

Thanks, bucketboy

I may try this on my AirMax 22 pistol

Ed

 

[bucketboy]

Drill 6 tiny holes, you can easily make them bigger, more difficult to make them smaller.



Bb

 

[SilentSquirrel]

Drill 6 tiny holes, you can easily make them bigger, more difficult to make them smaller.



Bb

I'm considering 3 to 5, 1/32" holes

5/32" is less than the .22 diameter (7/32"+)

 

[Hepotter]

I use 3 mm drill bits on the shrouds I have drilled in the past. They are cheap and sharp. I usually marked the shroud with a pencil to get the holes evenly spaced. Further, if you can, I suggest starting the drilling very slowly to ensure the drill bit doesn't "roll sideways" when starting the hole. Once you can see bare metal the bit tends to stay within the hole.

A word of warning, don't let the idea lull you into thinking "more is better"...that has never proven to be true. I suggest you limit your vents drilled to not exceed four to six in number. 

My personal experience has been too many holes create their own discharge sound. This kind of defeats the purpose of the effort.

Further...a permanent black Sharpie will nicely conceal the shiny metal which will show after the drilling process. Just put the Sharpie point into the hole and roll it with your fingers. Try not to get any black ink on the outside perimeter of the hole. This is cosmetic and nicely disguises the vents.



Hoot

 

[lipido]

Found these videos where they add sound dampening material inside the holes of the shroud, seems like a good idea.


https://www.youtube.com/watch?v=9Nukksc9c-0

https://www.youtube.com/watch?v=2YAfCwNBubw

Anyone tried this?



In the first video there are 24 holes, a lot more than the recommended max of 6.
So I guess the sound dampening/air flow restriction allows for more holes. Is that a good thing and where's the sweet spot?

 

[Guest]

You can use a punch or wrap shroud in tape before drilling. That will help prevent the drill bit from walking on you

 

[Xbowsniper]

Nation, 

For the guys with Benjamin Marauders, I recommend drilling a hole in the shroud for one reason with that particular gun.......Temperature shift.

The fitting towards the rear of the barrel, right out of the receiver, accepts the screw in shroud. This fitting has an o ring on it. There is also a fitting on the barrel, that centers the shroud, and it has another o ring on it.

In extreme temperatures, particularly warmer temperatures, the air inside of that part of the shroud gets pressurized, as slight as that may be. Drilling a small hole in the shroud somewhere along its length behind the end of the barrel, alleviates this pressure, and prevents the heating of the air within the shroud, thus torquing the barrel. For competition purposes, I don't care if the gun is loud or not, so I remove the shroud for better accuracy anyway.

Tom Holland 

Field Target Tech 

 

[Mr.H]

The first generation Donny FL moderators didn't have vent holes (I have a 1st Gen Sumo like this). But at some point Donny put vent holes on all his units.

Does anyone here have both generations? Do you notice a sound/tone difference with the vent holes?

 

[BigTinBoat]

Nation, 

For the guys with Benjamin Marauders, I recommend drilling a hole in the shroud for one reason with that particular gun.......Temperature shift.

The fitting towards the rear of the barrel, right out of the receiver, accepts the screw in shroud. This fitting has an o ring on it. There is also a fitting on the barrel, that centers the shroud, and it has another o ring on it.

In extreme temperatures, particularly warmer temperatures, the air inside of that part of the shroud gets pressurized, as slight as that may be. Drilling a small hole in the shroud somewhere along its length behind the end of the barrel, alleviates this pressure, and prevents the heating of the air within the shroud, thus torquing the barrel. For competition purposes, I don't care if the gun is loud or not, so I remove the shroud for better accuracy anyway.

Tom Holland 

Field Target Tech

That "front fitting" is a stripper, with (4)holes in it, leading from the shroud to the atmosphere. How in the world is it getting "pressurized" with those holes?

 

[westgl33]

This looks like a great way to reduce the report of my Marauder Synrod, and Marauder Pistol, and my Fortitude. if it actually has a Noticeable difference in the sound of the report. Following this.

 

[FuzzyGrub]

Nation, 

For the guys with Benjamin Marauders, I recommend drilling a hole in the shroud for one reason with that particular gun.......Temperature shift.

The fitting towards the rear of the barrel, right out of the receiver, accepts the screw in shroud. This fitting has an o ring on it. There is also a fitting on the barrel, that centers the shroud, and it has another o ring on it.

In extreme temperatures, particularly warmer temperatures, the air inside of that part of the shroud gets pressurized, as slight as that may be. Drilling a small hole in the shroud somewhere along its length behind the end of the barrel, alleviates this pressure, and prevents the heating of the air within the shroud, thus torquing the barrel. For competition purposes, I don't care if the gun is loud or not, so I remove the shroud for better accuracy anyway.

Tom Holland 

Field Target Tech

That "front fitting" is a stripper, with (4)holes in it, leading from the shroud to the atmosphere. How in the world is it getting "pressurized" with those holes?

It can't. I suspect something else was going on with temperature rise that led to the hypothesis that it was being pressurized.

 

[FuzzyGrub]

This looks like a great way to reduce the report of my Marauder Synrod, and Marauder Pistol, and my Fortitude. if it actually has a Noticeable difference in the sound of the report. Following this.

I have tried the holes in the shroud back by the breech and using open cell foam, like in the video's posted. Tried it on Mrod, Prods, and Libertys. In all cases it changed the tone, but didn't lower the over-all sound pressure. Adding length/space in front of the barrel muzzle always provided a better solution.

 

[westgl33]

I have read that loosening the Rear Barrel Shroud Mount and sliding it forward, some amount, and then retighten it in the forward postion (like on a Mrod , & Prod), to get more shroud space in front of the barrels muzzle was beneficial, to get more Sound waves into the shroud, and back behind the Muzzle. I have also been looking at adding some more strippers in the shroud, and modding them with various, and differing hole configurations to try and change, or cancel some of the sound waves.