Part Two: Horizontal venting of the Vulcan baffle stack…
:hoot:
In my last pontification, I advised the forum members how to add eight (8) vents in a circular pattern around the base of the Vulcan shroud. It made the gun quieter, but not quiet enough.
Now, I have finished putting four horizontal holes, 1.5 mm diameter, on each side of the baffle stack in the shroud.
Like this:
How does one get the horizontal holes to line up nicely when you screw the shroud back on, so they are even with the air tube below? No so hard. Just put an O-ring around the barrel and slide it all the way back. When you screw on the shroud, you can compress the O-ring and line the holes up nicely, where the pressure of the O-ring on the threads will hold them in place quite nicely.
Note the O-ring, and observe the evenly lined up holes with the air cylinder: (That’s primer paint on the shroud…later covered with black Rust-oleum Appliance Epoxy paint)
Compressed O-ring:
How does it look? Properly done, it doesn’t really show. This is not a good picture but it will have to do.
What was the outcome of this venting adventure?
In my personal opinion, the gun is now “neighbor friendly”, with the exception of the “Pingggg”. The muzzle blast is gone and when you hold your fingers near the vent holes, at either the base or the muzzle end of the shroud…you can feel LOTS of air pressure being released.
Is it as quiet as with an ldc added? I can’t honestly answer that question. All I can say is it’s quiet enough to shoot the .25 caliber at 880 fps near my touchy neighbors without them noticing.
When John Hagan releases his eccentric moderators, I am going to look really hard at them. They do the same thing as my vents, plus they add increased expansion volume in the shroud “can”. If they are too rich for my blood, I have the option of leaving the gun alone because it is now “quiet enough”.
Should you do this mod? Depends. Do you have access to a drill press, and a device to hold the round shroud tube in place, so the bit doesn’t wander all over the shroud surface? The horizontal holes were the most difficult to get lined up, marked, and drilled. Note they don’t have to be directly lined up with each baffle. It helps, because each baffle has a long side, with an O-ring above and below the holes in the sides of each baffle (it’s designed just like the Colibri baffles) These O-rings leave a small space between the baffle sides and the shroud walls. If you drill a vent hole anywhere in that space, you will vent a tremendous amount of air before it reaches the next up baffle. The result is a LOT less air pressure exiting the muzzle.
Done carefully, it looks nice. If the holes are uneven…it doesn’t look so nice. Then you have to fill the holes with JB Weld Steel Epoxy, sand it down, and start over. Be careful and this won’t be necessary! And…there is a paint on the market that matches the Vulcan close to perfectly, black Rust-Oleum Appliance Epoxy paint. So mistakes can be corrected if needed.
It’s sixteen holes, drill slow, do it carefully, mark your drill points ahead of time, use a new 1.5 mm bit.
I intend to add the Hagan hammer spring delrin bushing to further quiet down that annoying ping. I also am going to stop the resonance in the air tube…but more on these mods after they are done!
Slowly, carefully, the .25 Vulcan is turning into a great pcp…and it’s as quiet as the .22 now.
Hoot:
All Replies
Viewing 5 replies - 1 through 5 (of 5 total)
You can start with smaller holes and enlarge them later if they don’t produce the results you need.
Of interest is the Edgun that uses very small vent holes at the base of the shroud. His are probably in the .7 to .8 mm size range.
The original holes are 1.5 mm, you can go larger but eventually risk the escaping air making their own air blast. Larger is not always better.
Hoot:
Hey Hoot, are you sure you used a 1.5 mm bit on that shroud ? I just drilled mine both places like yours and my holes sure look smaller than yours . I used a 1/16 bit that should be slightly larger than 1.5mm. May just be the way the picture makes it look. Anyway, you are right a nice squirt of air escapes from the holes. Mine is a .22 and wasnt loud, I just did it to maybe help relieve pressure on the pellet for better accuracy.
Looks nice Hooter…….
Hoot the Vent Master….. I guess I have to try drilling vents in my own shrouds… just got 0.7mm drill bits. Is this too small?
Viewing 5 replies - 1 through 5 (of 5 total)
- You must be logged in to reply to this topic.
Nice work as usual magnificent Uncle :bow: :bow: :bow: :bow: :bow: :bow: :bow: :bow: :bow: :bow: :hoot: I have done some venting on my AF Condor and it helped tremendously. However I would probably drill my holes on the under belly of the shroud and not where it would be visible this is just me. in a horizontal line. Not sure if it would change the dynamic or not but for me I wouldn’t have to worry about the cosmetics.