You can shoot subsonic heavy bullet 22lr rounds that are quieter than a PCP with the same energy. Furthermore, you don't have to worry about running out of air.
I shot my career for a few years and switched to firearms because a 22lr is so much simpler and for me had no disadvantages.
Conrad..
It's 2013... Not 2001.
Crosman makes .17 to .35 cal ariguns with FACTRORY installed moderators /shrouds that screw right off. There is NO ATF caliber reg as to what is an is not legal on an Airgun which to the ATF is a NON FIREARM. Maybe in some of the more ant-gun statyesd like MI , CA or NJ that might be the case, but it's not Federal law.
Their doctrine is "intended use". As along as any silincer or shroud is designed for use ON AN AIRGUN and used ONLY ON AN AIRGUN then there is no violation of the law. It pretty much like the law regardijng putting shoulder stocks form T/C RIFLE carbine on a handgun length T/C and making an illegal short barreled rifle.
As long as your don't use the moderator for a non intended, illegal purpose you are fine. Most makers go the extra step of using attachment systems (grub screws) and lightly constructed internals that will not last more one shot a Powder gun. Crosman went ahead and threaded their Shrouds on. They are the FIRST us Arigun MGF to build an Airrifle with a intregal supressor.. I am sure thir legal dept thoroughly researched US case law regarding silncers before they made that move.
As far as a Silenced PCP in .25 on down, Decibel level meters have shown they are quieter than even a supressed .22 LR subsonice round. And there are guns currently out of the box (like the Mauraders) that WAY outperform an unmoderated Career model rifle in terms of Noise level.
