I have been making accessories for my airgun and I came out with a suppressor or a silencer (whatever you call it). I know you're gonna be asking whether it actually works or not but yea It actually works!
I also put a little bit of grease for insulation.
I don't have any videos to prove it but once you model and print the right adapter for your specific airgun it will reduce the sound quite well. You're gonna be surprised for sure :P
You can use it as a decoration like I do generally. Believe me it draws quite a lot attention.
Casing Diameter: 25 mm
Bore Diameter: 5 mm (It's for 4.5 mm airguns)
Bore Length: 138.5 mm
Casing Length: 120 mm
I also modeled a small version of it which has a casing length of 60 mm.
Esun PLA+ Black
Nozzle Diameter: 0.4 mm
Layer Height: 0.2 mm
Nozzle Temp: 205 C
Support: Only for screws
Brim Outlines: 6
You don't need any support structures for baffles (Search for baffles if you don't know what it is).
Slightly sanded with a fine sandpaper.
Can be made smoother optionally.