Making super tanks and super guns.

[Czynszol]

Hello people,one again i want to ask you for something.
On one video from You Tube, [don't really remember the title] i saw a IS-2 or IS-3 tank,shooting.Right,but not with his 122mm gun.Just with some rockets.Also,on World War Facts video from Ondkorven i saw the fact,where Tommy gun [Thompson machine pistol]destroyed japan tank,small one.
So,my basic questions:
-how to make tanks shoot other ammo/guns that they usually do
-how to make their basic gun damage bigger [if even possible]
-how to make Pistols,MPs,MGs,destroy tanks [or make their power bigger]

Thanks!
And sry if topic like this already exist.If it does,delete this but give me the link to the old one.

Greetings,
Czynszol