A retrofit kit for providing flexible paintball loading mechanism is disclosed. In one embodiment, the retrofit kit includes a right side portion of a receiver, a left side portion of the receiver, and a bottom removable adapter. The right side portion of a receiver having a first feed hatch is able to receive paintballs through an upper loading mechanism. The left side portion of the receiver after coupling with the right side portion of the receiver to form a receiver is capable of coupling to a barrel as well as a pressured gas container. The bottom removable adapter, in one embodiment, facilitates to receive paintballs via a bottom feeding mechanism.