Han's distinct sidearm, the DL-44 heavy blaster, was again made from a replica "Broomhandle" Mauser. It was manufactured by the Model Gun Corporation of Japan. The brown plastic grips were painted black.
1896 German "Broomhandle" Mauser Replica from MGC (Model Gun Corporation)
The design of this blaster is based on a resin stunt blaster used in filming The Empire Strikes Back. This is because the prop house in charge of building the ROTJ blasters were given ESB stunt blasters as reference.
The barrel was cut down and a flash suppressor was added. This part was custom made from some type of black material and painted silver. It attached to the barrel from underneath with a 8/32" socket head cap screw with a knurled head.
Two pieces very similar to the Revell piston halves used on the ESB version, possibly custom made to resemble the piston halves, were riveted onto one side of the gun. The opposite side has one of these pieces beneath the scope mount.
(ROTJ version) Piston Half (ESB version)
The square detail added between the screws of the scope mount is possibly a 3/4" black rubber foot. This same part can be found twice on the DH-17 (ROTJ version).
ROTJ Version Scope
The scope was cobbled together from a few different parts to resemble the M19 telescopes used in ESB. A real scope was cut down for the back half and a black cap was attached to the front with a single rivet through the top. The scope was attached to the mount with a cantilever scope ring, exact brand unknown. The mount is yet unidentified.
Note: Some photos show the front cap of the scope missing. This is because that part has broken off since filming, that is what the prop currently looks like.
Additional info: At least two props were made as described here, while a third firing version of the prop was built on a real Mauser with checkered wood grips and an aluminum muzzle.