5.56X45mm
Milforum Mac Daddy
What this video posted on Myspace.com. It will answer many questions.
http://vids.myspace.com/index.cfm?fuseaction=vids.individual&videoid=901319678&n=2
http://vids.myspace.com/index.cfm?fuseaction=vids.individual&videoid=901319678&n=2