I was able to get Binelli USA customer service to confirm in writing that 5.56 is ok for an MR1 with the ".223" stamped on the barrel.
It appears there are some import considerations and/or translation issues with european manufacturers of 5.56 capable rifles. the same type of confusion reins for other european imports of 5.56/.223. see the posts on the san sig 55x on the sig forum at:
http://sigforum.com/eve/forums/a/tpc/f/630601935/m/4090092552/p/1