So, I finally figured out how to snipe people out of their tanks. No, it's not about finding that super sweet secret thermal exhaust port. It's about distance. "Distance?" I hear you chime in with swiftly. Yes, distance my dear. This not only applies to tanks, but PVs (Player Vehicles) as well.
So what do I mean with all this distance nonsense? Beyond a certain point, (Around .20th of a mile from my personal experience) is the point at which the model of a PV, such as a car, or tank, will render, but for some reason, won't have a hit box of its own. "OOohhhh!" I hear you say. Yes, that's how it's done. Beyond this distance, it doesn't matter, .20 of a mile, .70 of a mile, and (in my farthest reaching test) 1.2 miles away, doesn't matter.
Try it yourself with a friend, get a tank, (Whether it be from Fort Zancudo, or a personal tank) and have your friend sit in the tank at a place around .20-.70 of a mile away from wherever it is you're going to snipe from. For this test, I chose the Richard's Majestic Hotel heli pad. (See picture below.)
From here, the 400k house can be seen from about .70m (we're gonna pretend that m stands for miles and not meters here) away. The red circles below represent where the tank is parked, unfortunately, the camera phone doesn't have a very high zoom...
From the south east corner of the Richard's Majestic Hotel, to this bridge, (as shown below) is about .20m away. You can just barely make out the car that is circled. (I shot a guy out of that through the upper left of the roof.) This is a great testing point for your tank sniping practice. It's very level, open, and you have a clear view of the tank/car you're practicing on.
The trick to a mile + shot, is simply looking for the health bar. Even though they're out of render distance, (people stop rendering after something stupidly small like 100 meters away.) their car they're in will still render even a mile away, albeit, very glitchily in some cases. (low res textures, jumping around, etc) Your greatest friend here, is hitscan. Every gun in the game is hitscan, even your sniper rifle is hitscan. What does this mean you ask? It means that you don't have to take ANYTHING into account; not distance, not velocity, not even the wind, NOTHING. You fire, and it hits ...instantly.
The easiest way to sniper targets at long range, is to simply leave your cross-hairs at a location in front of your traveling target, and fire when they drive through your cross-hairs.
Now remember, if you can see the health bar, then you can hit them, doesn't matter if they have their back to you, or their side. Your bullet will bypass the WHOLE car/tank, and hit the player inside. (The health bar isn't required, but just helps you find where their body/head is inside the tank.)
For some reason, even though the player model doesn't render at that distance, their hit box still does. Where as the vehicle's model renders, but has no hit box. Rockstar logic, lol. Not to mention, it seems to be MUCH easier to hit people at long range, almost as if your bullet is as big as your cross-hair's dot in the center. (At longer ranges, the dot can take up the whole driver side window of a car.
I hope this helped! I've already sniped 3 tanks, and a few passing cars on the freeway this way.
Edit 1: "To figure out the distance between two objects, simply set a waypoint from one to the other, and get into a car. It will tell you the distance between you and the other location in the lower right hand corner of the radar."
Edit 2: "I can confirm, that at close range, (below .20th of a mile) that the back left vent of the tank, is a weak point. What I mean by this, is that you can use this to snipe the driver out of his tank, just like a normal car window. Just wait for him to turn away from you, and pretend like you're sniping someone out of their car via the back left window. I have killed 4 tank drivers like this. One was right in front of me, almost touching me he was so close, so it most definitely works at close range lol."
"I haven't tested out the normal sniper rifle, but the heavy sniper most definitely can fire straight through the vent and into the operator's cabin. So I guess, the tank really does have a super weak thermal exhaust port, lol."
Edit 3: "After extensive testing, I can confirm that it's not only a specific point on the rear left venting, but it is in fact the ENTIRETY of the rear armor's grated venting that's weak to the heavy sniper's rounds. I tired from many different angles. As long as you have a straight angle through the rear vents, to the operator's seat, then you can kill the operator, regardless of distance. (At least, in my previous testing, just had a few tanks that I couldn't snipe from the back end today at close range. So perhaps they've patched it, or it was just dumb luck... oooorrrr a few God mode'ers.)"
Some helpful advice from SAVILLAIN with an image of the weak points of the tank.
did some tank bounty killing and people were getting mad at me for " just going after a low bounty kill " but who cares
so then I went into the lab and found the best places to take the tank out