Builder45, I've been interested in a subsonic 300 Whisper for some time now built on a Contender pistol.
Bullet placement will be important using a narrow 30cal projectile at slow speeds. So I'm thinking a bullet with a larger frontal area would be more effective. Like a 45 long colt loaded with a Hornady 350gr flatpoint or similiar weight bullet. That should have some shock value on a whitetail.
You may also need to have a scope with target knobs depending on how far you shoot due to the trajectory of a subsonic round.
http://www.quarterbore.com/300whisper/
http://www.lasc.us/RangingShotLongWhisper.htm
Since the AWB has ended, this has become more interesting:
http://www.model1sales.com/item-deta...u16carpre3.gif
Allen