R-9 Moderator

Slip on adapters for 16mm barrels like an R9 are available on Ebay and through many European distributors. However, most of the noise from an R9 is mechanical noise from the spring and piston slam, not air discharging. Spring guns do not benefit from moderators to a noticeable extent. Don't bother, as you'd be disappointed in the results. PCP's make much less mechanical noise but much more air is discharged per shot. They benefit from moderators much more than a spring powered rifle does.