Here's the TECTEN my design for a Talon magazine fed Nerf Rival Knockout modification. It replaces the Body and chambering system.

NOTES: ALL TOLERANCES ARE TIGHT ON PURPOSE, you should not need glue or epoxy unless you want. Charging handle and PT Adapter are friction fit. Barrel will need to be fixed into place. Charging handle is reversible for LEFT or RIGHT hand use. Stock Locks are left in blaster to avoid crushing the brass bolt

You will need" Barrel ** 9/16" brass Bolt ** 17/32" Brass Cut to approximately 4.25 inches in length PTAdapter brass ** 9/16" cut to length of the PT ADAPTER and press fit into it. a small rubber oring silicon lubricant m3 screws misc lengths.