Take a look at the Aquila rimfire ammo. They make a subsonic round
with a 60 grain bullet. Real quiet and packs quite a wallop. They
have an amazingly un-user friendly website. http://www.aguilaammo.com
is the company, to see the ammo you need to end up at
http://shop.sisna.com/centurionordna...Name=R imfire

Accuracy through a standard twist barrel is OK. For real performance
you need a slower rate of twist, but then you are getting into a
pricey rifle.

..22 SSS-Sniper Subsonic/Brick 500rds
$40.00 a brick + S/H
60gr Solid Point Lead Bullet. Velocity: 950fps. Energy: 120Ft-lb.