http://www.bergerbullets.com/twist-rate-calculator/ This site gives some good info for those questions.
If you need to look up your bullet length then this site has a good list
http://www.jbmballistics.com/ballist.../lengths.shtml
Ive shot my personal best group ever out of my 300 wm with the eldx 212's they seem to group well I'll give them a try on some game this season and see how they preform expansion and retention wise.