.25 moderator on a .22 gun?

[cavedweller]

This STO .30 high flow moderator on my Alphawolf .177 shooting 10.3’s at 890 is fffft quiet but same mod on the same gun pushing a 44.75 @ 890 is gonna make a good crack

 

[Stubbers]

Don’t forget absorbent materials and things which slow expansion

I prefer baffles that vent into felt held by a cage / chicken wire or something to keep it from ever entering the pellets path, akin to using a pillow as a muffler, much more pleasant than having the sound waves hit solid walls, IME.

-Matt

 

[subscriber]

Don’t forget absorbent materials and things which slow expansion

If you choke off the vent holes with absorbent materials, the actual flow from the vents is insignificant; and the leaked noise with it. People advocating that you drill holes in the rear of your shroud invariable tell you to stuff fibrous material in around the vents. The benefit of sound absorbent materials exists without the need for extra vents. So, try just the stuffing the rear of your shroud, first, before drilling extra holes. Without substantially blocking off the extra holes with fiber, the extra holes make the front of your airgun quieter by making the rear louder.

I am a proponent of mufflers with double walls, where the inner wall is heavily perforated, while the outer wall is unperforated.

As always, the devil is in the details. The small number of tiny holes in the typical DonnyFL moderator casing don't leak sound because very little air can flow out of them. Also, because there is felt blocking them off, and because of the short time interval where the pressure inside the muffler is significant. In other words, those vents don't hurt, nor do they help. They are like pin stripes. Their sound reduction works on the principle of "Placebo Domingo".

Look inside an engine exhaust muffler. Note that the perforated tubes are all inside an unperforated casing - for very good reason.

I had a guy on this forum tell me that his main concern is about sound in the direction he is shooting. So, he does not mind making more noise to the side and rear in exchange for less intense forward directional noise. That is a reasonable argument for side vents.

 

[Jay308]

The DonnyFL sizes are:

The .177/.22 is for a shrouded .177 or direct threaded in .22.
The .22/.25 is for a shrouded .22 or direct threaded in .25.
The .25/.30 is for a shrouded .25 or direct threaded in .30.

The shroud alignment could be off, compared to threads directly on the actual barrel. The new sizes are already up sized and ordering a size up is not needed anymore. This is how it was explained by DonnyFL.