I'm going to guess there's some very gross exaggeration with this story. KT has 225 rear armor. T3485 has 160 penetration and T3476 has 120, so that's 71.1% and 53.3% respectively. 75 seconds is enough for each of your tanks to fire approx 12 times, so 36 shots.
36 X 160 dmg = 5760. Even if only 1 in 4 shells penetrated - and you'd be expecting much, much more than that- the KT would die.
Note: i think OP exaggerates, there are other factors or there is a HUGE fluke on RNG. But some considerations to add:
1- KT needs 3 and 4 shots to kill either tank. It needs 2 or 3 shots to disable them with crits. This will reduce the number of shots.
13s to disable a T76 and 19s to kill it
19s to disable a T85 and 25s to kill it. A single faust/shreck or just 80hp not repaired, would move up the TTK to 19s.
2- T3485s were on the sides which means it can be hitting either side or frontal armor depending on positioning. Just go for a 50/50 on most cases. But if IIRC the distribution on heavies is more of a 75/25.
42.6% in case of frontal shots.
Note: i'll assume no miss nor 76s shots scattering to frontal.
3- With what i previously said, lets assume this.
-KT will kill T85 on the right, then go for the T76 and then the other T85.
-One 85 will land 12shots, 76 will land 7shots and the other T85 4shots.
-We could add an extra shot on each T34 as they aproach the KT but it might roll misses as they are on the move.
-You need 8 shots to kill a KT at 160dmg.
>We have 8 shots with 71%, 8 shots with 42.6% and 7 shots with 53% (in case of 50/50 side armor)
>We have 4 shots with 71%, 12 shots with 42.6% and 7 shots with 53% (in case of 75/25 side armor)
|On average you are penetrating case1: 13shots case2: 12shots
BUT what if we take into account a bad rolls and "side armor" distribution
Well, landing 2/4 with 71%, 3/12 with 42.6% and 3/7 with 53% you have barely enough to kill a KT. A slight worst roll on any tank and boom enough to survive and kill all 3 tanks.
TL;DR:
-It's not as crazy as it sounds.
-There's no side armor so probably more than 50% of shots are frontal
-A bad RNG roll but not as bad as you think makes it possible.