Whomever that I took the chassis from, great job. Nice suspension. Only downside .... the vehicle hull angle when the spade is not deployed?

Basic gunnery intro

Now, as many of those out there that make "tanks"(includes Jundroo), the basic elements of the gun are usually (if not always) ignored. To re-create the accurate mechanism, we need to answer a question:

What is recoil?

Recoil is the counter-force created after ejecting the shell from the cannon. It is required to be effectively transmitted to the hull and spade to be stopped.

How?

To do that, the barrel (and the loading breech) is connected to a suspension-like recoil-dampen system. It can be done wither using either springs (suspension) or as more real-life counterpart suggests, pneumatic damping system (which is suspension)
The pneumatic ones clearly had some advantage such as decreased size, but for now we don't really have "access" to that ...
The rails that assist reloading the shell is connected to the base of the gun and will not recoil back.

why do I create this NOW

The introduction of modding had ... led my experiments to create such concept, and mounted on a ... more or less average hull for the demo of it.
To be honest, the gun sounded fine. you know. Echoing was more or less irrelevant. Chassis is nice but inaccurate, but more or less fits the scheme.
Group 1 for driving mode, I assume, and group 2 for aiming of the accurate gun (somehow laser guided) and landing gear for the spade (to stop recoil)
Have fun shooting!