What's Old Is New Again
It seems the Army thought the 1911 was too difficult to hand cycle the slide with the hammer down. As expected, manipulating the mechanics to acommodate user weakness resulted in functional weakness of the mechanism.
Chris Byrne gives his thoughts as well.
More on altering percieved 1911 recoil through firing pin stop manipulation can be found here.
Evolution Gun Works stocks the part. Fifteen bucks and a bit of file work, and Bob's your Uncle.