The M103 is quite a beast but mostly has the same weak spots as it’s predecessors. If you’re not looking down its barrel and the front of the hull you’re well off on the path of its destruction.
The front is extremely strong, except straight down the middle of the hull, where you can try to get an angle on the driver, or the commanders hatch on the top of the turret if you have the guts for that while staring down that big gun.
The sides on the other hand contrast the hardness of the front with there being quite a light show, should you hit the ammo rack on the sides of the turret and the front of the hull or the engine in the back.
The back is quite riddled as well except for the left of the turret where it’s a bit harder.
The ammo rack is located on the front of the sides of the hull and the front of the sides of the turret.