5.56x45mm "Duplex" Colt
Phase 3,  
"Yellow Tip"
for "Fluoroscoped"
In the late 1980s Colt & Winchester
submitted a few different experimental
"Duplex" (2 projectiles to the cartridge,
one behind the other) to the US
Military Trials. These are one type for
those "Phase III" experimental trial
This cartridge has a "YELLOW TIP"
as  it was "Fluoroscoped" which refers
to the fact the rounds were run under
an X-ray to insure the second lower
projectile was alined straight with the
neck of the case behind the first
The idea of the duplex cartridge loading
is to launch two projectiles per firing to
increase the odds of hitting the target
(and/or) two holes in the enemy is
better than one.
I believe they would of had problems
keeping the second projectile in place
inside the case without the extended
neck version and the  idea never really
caught on; (to my  limited knowledge)
the U.S. Military does not use or have
any duplex cartridges in  their arsenal.
Head Stamped WCC 88 for
Winchester, 1988
$ 29.75 per