the 90gr XTP (.309) has been loaded successfully in bolt and single shots by many. its a good lightweight sub load - and supposedly can be mouse fart quiet - and at supersonic velocity's is quite explosive from the video's i've seen.
they wont however feed reliably in an AR platform
http://www.hornady.com/store/.309-30-Cal
[edit] you may find this post usefull to you regarding them
http://www.300blktalk.com/forum/viewtopic.php?f=141&t=96148
