We have a handy little guide for Battlefield 4 players on the tank reticle and recommendations in using shells.
First off, here’s a handy little reference on the tank reticles itself. You can see the differences between AP and HE shell ranges.
Now that that’s out of the way, there’s a lively discussion on HE shells vs Sabot shells. There is no consensus on some points, but what we’ll pick out here is what many players agree on, and is more likely to be true. You may have to take the information here with a grain of salt, but you may find it useful.
We can establish that HE shells do more damage per shot, but have a slow speed and poor trajectory compared to the default. Many players swear by mastering and using only the HE shell. However, the HE shells do not have great range, and you will have to adjust to its radically different trajectory.
On the other hand, the Sabot has speed, range and is easy to use against moving targets, such as choppers. If you pair it with HMGs, those can take care of infantry for you. One player compares it to being the long range sniper of tanks.
Ultimately, your choice goes down to what you want to do with the tank. Some players point out tanks aren’t meant to snipe tanks, and HE shells are sufficient for what they are supposed to do, but it seems it would be good if you had the skills to use them either way.
Here's another look at the HE shell ranges, layered over the actual reticule as seen in game.
Source: Reddit
