SIG 33 Self-Propelled Artillery

The sIG 33 Self-propelled Artillery were a series of self-propelled mounts for the German sIG 33 howitzer. They first appeared in 1940, and improved versions were still in production in 1944.

History
The Invasion of Poland had shown that the sIG 33s assigned to the infantry gun companies of the motorized infantry regiments had difficulties keeping up with the tanks during combat. The easiest solution was to use a spare tank chassis to carry it into battle. It was first mounted on a Panzer I chassis and given a lightly armored superstructure. This produced an adequate vehicle, but the center of gravity was very high, and the chassis was overloaded. As a result only a few dozen were built. Since the over-loaded Panzer I chassis was too small for the gun, production switched to models using the chassis of larger, more suitable tanks. In 1942 the PzKpfw II chassis was modified to accept the sIG 33. This version also received better armour protection. Eventually production switched to a modified version of the PzKpfw III and later still to the Panzer 38(t).

Guns
The early vehicles used ordinary sIG 33s, but an sIG 33/1 was developed for use on later vehicles although it's unknown what the changes were from the original model. The 15 cm Sturmhaubitze 43 gun used on the Sturmpanzer IV was an entirely new design developed by Skoda that used the same ammunition as the sIG 33.