I don't think it would be quiet enough for the needs specified in this thread, but I have been very impressed with the .204. Light, accurate, and packs a serious punch.
Also, take a look at the Ruger .204. It's just a touch louder than the .17 MACH 2 but will touch up VERY accurately out to 250 or so.
Good to see another liking the .204... It really is a great caliber.
