Making the factory FX stackable moderator more effective

Inspired by a video posted by Ernest about a DonnyFL moderator mod on how to make it even more effective, I did a similar mod to the factory FX stackable moderator that many choose to just discard or sell. 


I used some standard Walmart hair curlers and a soft foam piece. The foam is about 3/4 thick and will be compressed against the inside walls of the moderator. Cut it to size and wrap around the black hair curler. Cut the black curler to size if necessary (depends how many stacks make up your moderator). You may not need the larger spring (inside the pink curler) but I used it at the discharge end of the moderator to keep everything snug inside and to help press out the foam against the inside wall.

I was not able to test it yet, but it basically does the same thing Ernest did in his video.

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Was not able to take the gun out to the range, so compared indoors how effective the mod is. Not happy with the results, because I suspect that an iPhone app ("Decibel X") is not the most reliable way to get meaningful data unless the sound differences are already huge. Need to buy a reasonably priced decibel meter.
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Tested in a small room with some reverberations, backstop was 5 feet away, iPhone placed 1 foot from end of barrel/mod 90 degrees to the right. Pellet .25 JSB 26gr, velocity(? estimate 860fps), power dial at "C" setting with reg showing 150bar (accuracy of reg gauge not verified).
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For what it's worth here are the results:
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1. Stack-on mod taken OFF (only with shroud/stripper): avg. 102 db
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2. Stack-on mod ON and with foam insert/curler/spring: avg. 94 db
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3. Stack-on mod ON, factory (hollow/empty): avg. 95.5 db
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4. Bare barrel with early DonnyFL mod (7. 3/4in L x 1.5in dia): 94.5 db
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Again, these numbers are so close that I suspect the iPhone app is not the proper way to get a decent comparison. So I would not make any decisions based on these numbers. Need a dedicated decibel meter and a space without echos. Also, take note that the pitch of the sound can make a huge difference, so even if the decibel measurement is the same, a lower frequency sound may sound much lower.