>>329692
really all the parts that worked got implemented.
the "hit probability" centric model of improvement was really really dumb. flechettes are bad at wounding and inaccurate, duplex rounds wear out barrels and don't preform well, 2x integrated optics are crap.
here's a list of the long history of duplex ammo
http://www.thegunzone.com/salvo.html
and a history of the SPIW and ACR program, it goes all the way back to the 50s
http://www.thegunzone.com/spiw.html