On the potential to reduce muzzle blast of the .25 Vulcan…

:hoot:

3/4″ up from the base of the shroud, drill eight (8) evenly spaced 1.5 mm holes around the shroud. More is not better, larger is not better. Mark each drill point with a pencil to ensure the vents are evenly spaced before you drill.

Try hard to keep the holes in an even, perfect circle. Wrap masking tape evenly around the shroud to use as a guideline, better yet, make two wrappings about 1/16″ apart to keep the holes in a near perfect circle. When done, go very slow and use a sharp new 1.5 mm drill bit, you can touch up the holes with a sharp point black permanent marking pen when done.

Does it work? On the .25 it makes a difference. If you add an LDC on the end with John’s Hagan’s adapter, or some other means, it will reduce noise to very low levels. In my opinion, very much below “neighbor friendly” levels, provided the LDC is of reasonable quality.

The Vulcan shroud has two crescent shaped internal vents where the shroud screws on to the threaded barrel end. This is about half way up the shroud tube. These two internal vents permit high pressure air to flow to the back half of the shroud, where it can expand. By adding these eight small vents, the air pressure blowing out of the muzzle is reduced by the volume of the air vented out these small back vents.

It’s not magic, just simple physics. Lower the muzzle exhaust air pressure and you reduce the muzzle blast.

Another possible method is to pull a “Colibri” and put vents in the front part of the shroud where the middle of each baffle fits. Each NEW MODEL Vulcan baffle is cone shaped and has two opposing holes cut in the middle section of the baffle. In front of, and behind, these two opposing holes are tiny O-rings that seal each baffle to the shroud wall. Those holes, and corresponding O-rings, serve no purpose I’m aware of unless vented to the outside.

Measured carefully, you can put a tiny vent hole on each side of the shroud where each interior baffle hole is located. In doing so, you will reduce the air pressure hitting each next up baffle. It is critical that these front vent holes be very small…1.0 mm to 1.5 mm, again more or larger is not better. Don’t over do it…you will create more sound than you suppress.

To get a pleasing appearance, it is critical that the holes running horizontally back be in a straight line on each side of the shroud. Again, masking tape can help you visualize how even your drill points are lined up.

To keep the vents horizontally even to the sides of the gun may require use of thin shims between the breech block and the back end of the shroud. Each shim would reduce how far the shroud could be screwed down, thus enabling you to get the holes lined up evenly along the sides of your gun. The shims could be made out of just about anything, as they don’t bear any pressure beyond being compressed by tightening the shroud. It would be a good idea to check closeup pictures of a Colibri shroud to see how it is arranged. I have not tried this personally, so think carefully before you decide to do it!

No…I do not know what will happen if you vent both the front baffles and the closed back half of the shroud. If the holes are small enough they should not permit enough air to exhaust and create any noticeable sound.

I know this process to work with rear vents. I have no data on the front vents, except for my experience with the similarly vented Colibri which was one of the quietest air guns I ever shot. Their baffles were the same basic design as the current Vulcan baffles.

DON’T use larger vent holes than recommended. Too large, and each hole will create a tiny muzzle blast of it’s own, and you will have defeated your purpose.

Use your own judgement as to whether you should do this to your shroud. I wouldn’t do it if your Vucan is smaller than .25 caliber. I cannot guarantee your personal results. I can only report what I know to be a fact from experience.

Hoot:

PS: If you use the Hagan shroud adapter, and find you cannot get your LDC unscrewed because the adapter unscrews from the shroud first, you have the option of cleaning the anti-seize compound from the large shroud end of the adapter, and using a light hold Loc-Tite product to firmly hold the adapter in the shroud. After it dries, you can easily unscrew your LDC from the front threads and put your adapter cap back on. Be aware that later removing the adapter from the shroud, even with the lightest hold Loc-Tite, may be problematic because the adapter end is very slick, and there’s not much surface to grip when removing it.

Use your best judgement before doing this, it’s simply a technique I know that has worked in getting a stuck LDC off. I cannot guarantee your results.

UPDATE….

Adapter: Hagantool@aol.com
LDC: Donnfl@gmail.com