Original article by @rocketbrainsurgeon
This is patch 8.9 nearing 8.10. I'll tell you why HEAT premium rounds are terrible.
HEAT ROUND MECHANICS
Here are the main points, greatly simplified:
- AP gets a bonus against angled armor
- The steeper the angle, the better this bonus performs
- APCR gets a bonus against angled armor, but half as much as AP
- HEAT/HE does not get a bonus against angled armor
- HEAT can't penetrate spaced armor. Tracks and mantlets count as spaced armor!
- All armor that you shoot at will be angled in some way
LET'S SEE IT IN ACTION
The E-100 is a great tank for this example.
We are in the Chinese tier 8 medium tank, the T-34-2 with the 122mm gun. This gun has 175 penetration with AP rounds and 250mm penetration with HEAT rounds.
We are looking at the side of an E-100:
I'm simplifying the armor layout of the tank, but basically we have just enough penetration to go through the side of the turret but it's a 50/50 proposition. But we get a bonus against angles! The side of the turret is 150mm thick armor angled at 30 degrees, giving 173mm effective armor (go here if you want to play with angles and armor thickness). So the normal AP round treats it as 150mm thick armor at 25 degrees, down from 30, giving effective armor thickness of 165 penetration. So the hidden bonus to AP shells gives us an extra 8mm of penetration! The steeper the angle, the more effect this bonus has since armor can get exponentially tougher with angles (read my post above on "angling armor" to see why).
So we actually have enough penetration on the AP round to go through more often than not. We can load up a HEAT round with its' 250mm penetration if we want, but it's not necessary.
But see those tracks down below labeled as "200m+ effective armor"? That whole area counts as spaced armor. If a HEAT shell hits anywhere in the lower red section, it's not going to damage. However, sometimes an AP round would get a high penetration roll and still go through the tracks if the shot went low. But not a HEAT shell!
LET'S SEE IT IN ACTION, PART 2
The E-100 is now at roughly a 45 degree angle to us, which increases his effective armor. Here is what would happen if we shot AP rounds from a 175mm penetration gun at this E-100:
The armor is just too tough, and too angled for our 175mm penetration AP rounds. Let's see what would happen with 250mm HEAT rounds:
The exact same thing! So against very difficult targets, these HEAT rounds aren't going to be any more effective than AP. That's OK, because APCR wouldn't be worthwhile either: this example is just too difficult for most guns to deal with.
LET'S SEE IT IN ACTION, PART 3
This next image is taken from the excellent E-100 weak spot guide at wotguru.com. Highly recommend you check his site out!
- Can't penetrate the turret: 289mm effective armor is too much for both our AP (175mm pen) and HEAT (250mm pen).
- Can't penetrate the upper front plate: 400mm effective armor is way too much for our gun.
- We can penetrate the lower plate, but only with the HEAT round and only from dead-straight: as the E-100 turns away from us, the effective armor value quickly makes our HEAT shell ineffective!
HEAT VS APCR
HEAT shells have roughly the same penetration as APCR. But APCR shells get the bonus against angles and don't have weakness against spaced armor! So APCR is plain better than HEAT, no matter how you look at it.
So in the example we've been looking at, we were using the 122mm gun on the T-34-2. Looking at the AMX 13 90, it has 170 base penetration, and its' APCR round has 248 penetration. But since APCR gets the bonus, the 13 90's gun will have much more effective premium ammo usage.
- AP shells get a hidden bonus against angles... and there are always angles
- HEAT shells get eaten by tracks, mantlets, and spaced armor. Oh, and the tracks on the sides of tanks take up nearly the entire side of the tank
- HEAT shells don't have enough penetration to punch through tough turrets, and the shots can be eaten by the spaced armor in the mantlet
- HEAT shells have problems with angled armor
So if you want HEAT to work, you just have to shoot at un-angled, non-spaced armor that's only slightly tougher than what you can penetrate with AP. And be very careful when shooting at a turret or the side of a tank as the mantlet or tracks could just eat the shot. And you have to pay 5 to 20 times the price. Sigh... HEAT is bad.