WHAT DOES COLT COMBAT UNIT RAIL GUN 45 MEAN?

Lately I've noticed A good number of uppers which have been acquire offs from rebuilt M16A1 rifles currently being offered as "new replacement uppers".These are very good to go.I obtained a Hydra-Matic eighty% lessen from them a couple of calendar year in the past and end was great,engraving was superior and it went alongside one another easily wor