HaveBlue tried to use the same lower receiver to make a full-blown .223 AR-15/M16 rifle (Opens in a new window), but it didn't work. Funnily enough, he thinks the off-the-shelf parts are causing ...

Army engineers and scientists optimized the EPM to work with the M4/M4A1, M16 ... carbine's lower receiver that positions rounds for feeding. The forward moving bolt and bolt carrier assembly ...