Most people now know you can snipe a tank driver from a hundred yards away on the driver's hatch to take out a tank.
Although not many people know that the grill vents on the back of the Rhino Tank is the actual weak spot for explosions, heavy sniper bullets and minigun bullets.
It looks like attacking the tank from the back of the grill vents maybe halves the amount needed ammo to destroy it. It's not that big giant panel on the tank specifically, but pretty much the rear side of the tank in general.
However if you try shooting the tank from the front, rotating tank hull top and the sides then it, it would take forever since those parts of the tank are bulletproof or would take a long while before smoke damage would start appearing.
If you spray bullets with a minigun on the sides or frontside of a tank, you won't see any smoke damage appear at all, even after over 2000+ rounds. It's almost or probably bulletproof on those sides.
But if you were to shoot a minigun on the back grill vents of a tank, it would take about 900 rounds to blow it up. For a heavy sniper, takes about 83 shots to destroy a tank shooting from the back grill vents, although I'm sure it would be the same if you were to shoot it from over 100 yards away from any side due to the bullet physics glitch.
So here are my statistics of ammo needed to blow up a tank. The amount needed to destroy tank from the backside of the vent grills will be edited here
(any damage from the front or side doubles the amount required to blow it up. For example, 4 sticky bombs from the back would be 8 sticky bombs from the front or side)
(This was tested in the Deathmatch Creator mode)
RPG = 4 rockets (ex. 8 rockets if shot at from the front or side)
Grenade Launcher = (best accurate and fastest weapon to use against a tank on foot) = 4 grenades
Grenades = 4
Sticky Bombs = 4
Minigun = Around 900 bullets
Heavy Sniper = 83 bullets (which is 14 full 6 bullet clips) (do not need to shoot the back vent if you are sniping over 100 yards away due to bullet/car physics glitch)
Lazer Jet Machine Gun Cannons = 12 single shots
Buzzard Helicopter Rockets = 3
Rhino Tank Gun Cannon = 3
long story short =
ALWAYS AIM FOR THE BACK GRILL VENTED SIDE OF THE TANK
And use a grenade launcher, because it takes less than 5 seconds to destroy a tank with it!