You are referring to two different props in your pictures...the first one is Luke rifle from ANH, the second one is a rifle, which the Tuskens used in the PT.
The OT rifle was based on an arabian/ oriental Jambai or Camel rifle. I have a similar one in my collection, but the accurate version has never been found afaik. I have been told, that there even was such a rifle offered by Denix at some point. It features known details such as a few power cylinders, the square button also used on the DDCD and the MerrSonn and other greeblies.
The PT rifle was completely scratchbuilt.