All M4A1+ components will need to be compatible with current M4A1 ancillary equipment such as optics, aiming/pointing devices, training devices, slings and rail covers. One of the upgrades is an ...

All M4A1+ components will need to be compatible with current M4A1 ancillary equipment such as optics, aiming/pointing devices, training devices, slings and rail covers.

And if that weren't enough, the Army's solicitation for bids specifies that "the M4A1+ components will be evaluated as a system. The system must then install on/interface with stock M4A1 Carbines." ...

The Army’s industry solicitation states: “The M4A1+ components shall provide a synergistic effect to enhance soldier and weapon system lethality, survivability, and operational effectiveness.” ...

What makes Colt’s M4A1 so remarkable is the night-and-day difference between how this gun is manufactured compared to every other Colt firearm. You have to see it to appreciate it.

And if that weren't enough, the Army's solicitation for bids specifies that "the M4A1+ components will be evaluated as a system. The system must then install on/interface with stock M4A1 Carbines." ...