SU-76-57 Self Propelled Artillery

The SU-76-57 was a SU-76M with a 57 mm ZiS-2. A second version was proposed with a fully enclosed upper structure
1.
Name: SU-76-57
Type: Self Propelled Artillery
Origin: Soviet Union
Year: 1944
Produced: 1 (possibly 2)

Length: 4.96 Meters
Width: 2.71 Meters
Height: 2.1 Meters
Weight: 10500 Kilograms
Speed: 40 km/h

Crew: 4

Primary Armament:
-57 mm ZiS-2
Secondary Armament:
-7.62 mm DT

Gun Flexibility:
17° Elevation
4° Depression
15° Left
15° Right

Armor:
-Hull
35 mm Front
25 mm Side
15 mm Rear
10 mm Top
7 mm Bottom
-Upper Structure
25 mm Front
15 mm Rear (fully enclosed version)
6-8 mm Top (fully enclosed version)

Source:
http://www.aviarmor.net/tww2/tanks/ussr/su-76.htm
http://www.tanks-encyclopedia.com/ww2/soviet/soviet_SU-76.php
http://tankarchives.blogspot.ca/2017/03/su-76-57.html