I shot two does one morning last year with my AR
Read here for more info:
http://www.thefiringline.com/forums/showthread.php?t=329141
Read here for more info:
http://www.thefiringline.com/forums/showthread.php?t=329141
If a 324fps arrow will harvest most game in the US, then just about most calibers will work.
I wouldn't be comfortable with a newbie reading some of these posts that say a rimfire is adequate. Absolutely it can be done (quite easily), but shot selection is critical and timing of deer movement is paramount.