EPISODE IV: A NEW HOPE
Used by: Sandtrooper

On the scorched dirtball known as Tatooine, Imperial Sandtroopers carry this weapon to keep the locals in line. Two are seen in the photo from Mos Eisley above, it is the standard heavy blaster rifle of the Sandtrooper.

In reality the prop was a German MG-15 machine gun with two scopes added on top. The spiderweb-like front sight and bipod were removed as was the large ring around the muzzle (which is the forward bipod mount).

MG-15 Machine Gun

The MG-15 was developed in 1932 and early on was extensively used on the aircraft of the German Air Force. By World War II, most were replaced and pressed into service by ground troops with the addition of a stock and bipod. It was known for it's 75 round capacity "doppeltrommel" saddle drum magazine, but proved clumsy as a ground weapon, leading to the development of the MG-34 (also used as an Imperial weapon, see the BlasTech DLT-19).

Length: 1335 mm (52.5 in.)
Weight: 12.7kg (28 lb.) with stock and bipod

The two scopes added onto the prop are not yet identified. The large brass scope on the back is almost definitely military. The front scope appears to be made for a hunting rifle.

This blaster is featured in three key scenes from Star Wars: A New Hope.
   - Searching the Tantive IV escape pod for the Death Star Plans
   - Stopping Luke and company at the Mos Eisley roadblock
   - During the Millennium Falcon's escape from Docking Bay 94

"anyone else hear an unauthorized liftoff?"

While just as common on Tatooine as the BlasTech DLT-19 heavy blaster rifle, to our knowledge this gun has never been given an official name in any Lucasfilm source.