Here are some armored vehicles, tracked, hard to categorize.
Have the appearance - - somewhat - - of a tank, but possessing that unusual, stubby, little barrel.
1. Churchill AVRE (Armoured Vehicle Royal Engineers).
A combat engineering vehicle [CEV] of the World War Two [WW2].
Designed for the specific purpose of providing protection and firepower for engineers attempting to destroy fortifications, concrete or other, impediments to tank or infantry advance.
"A Churchill III or IV equipped with the Petard, a 290 mm Spigot mortar, throwing the 40 lb (18 kg) "Flying dustbin" with its 28 pound high explosive warhead; a weapon designed for the quick levelling of fortifications"
Were able to take out with one shot an anti-tank wall, a concrete bunker, etc.
That stubby little barrel being a spigot mortar, NOT a gun!!
A weapons system having a distinct disadvantage! Dangerous in combat if you did not achieve a "kill" with the first shot!!
"the loader (the hull gunner) . . . had to stick his head and torso out of the Spigot Mortar armed AVRE to load the Mortar."
This particular photo shows a crew member of the AVRE straddling the stubby barrel with a "round" as fired from the spigot mortar in the right of the picture. NOT an easy item to service in combat!!
2. Sturmtiger . German assault gun from the WW2 era. Designed specifically to provide fire support for the infantry during urban combat. Fired a rocket of prodigious proportions [380 mm or 15 inch]!!
"Sturmtiger is the common name of a World War II German assault gun built on [a] Tiger I chassis and armed with a large naval rocket launcher [38 cm]. Its primary task was to provide heavy fire support for infantry units fighting in urban areas."
Ungainly looking armored combat vehicle based upon the same chassis as was used by the Tiger tank. That naval rocket being used in the direct fire mode during urban combat, ABLE TO TAKE DOWN AN ENTIRE LARGE-SIZE BUILDING WITH A SINGLE SHOT!!
Also cannot have been an easy weapons system to employ in combat. To load one "round" required an integral hoist assembly to be mounted on the vehicle, a crew of five men needed to load one round!! Again, cannot have been an easy item to use in combat. But all you needed was one round and that was that?
Just look at the size of that rocket!!
It could be suggested that the Sturmtiger was the ideal National Socialist [Nazi] weapons system? Allowed for TOTAL AND FINAL OBLITERATION of your opposition, remorseless, without finesse?