It seems to me that the biggest weakness of the 5.56/223 for military use is that it is FMJ.  I/we are not limited to FMJ, so why not load up on soft/hollow point?  Other than price, but really, its not really that much more and the performance is so much the better.  

Just my thoughts.  I still use bulk FMJ for practice but for "loading up on," i like 60GR soft points.  (60GR nosler partitions would be the ticket but $$$$$)

A FMJ will generally feed more reliably ,buy small amounts of different SP and HP rounds and see if either makes your weapon choke.