Technically no. If you are at the enemy's 3-o clock, your only chance of hitting an opponents rear armour is if you "miss" (not a typo) -- or if the engine bugs (like it sometimes does)
If your accuracy roll succeeds, the angle that your projectile will collide against the enemy is fixed. Thus, hit-rolls will either 100% hit front armour or 100% rear armour. Depending on your position.
(if you were at their 4-o'-clock, that would be a rear-armour hit 100% of the time)
Tank projectiles that miss might still collide with the original target. If it's a scatter roll, then, and only then, does your calculation apply.
Thus, there are 3 possible outcomes:
- A hit (100% rear or 100% front)
- A complete miss
- A scatter-hit (50% front, 50% rear, at 3-o-clock)
Note scatter rolls are NOT heat-seeking projectiles. Thus, if the target is very highly-mobile and moving away, they can dodge these projectiles.
There are a lot of assumptions in here.
I assume a direct hit means hitting exactly center mass which would mean that the front or rear hit would be dependent on the angle of the origin of the shot, as you had said. Even if your right, close range for the t34/76 only 5% of shots fired are direct hits, the other 95% go into the scatter table. Any hits delivered from the scatter table have a equal chance of being distributed across the front and rear of the armour at 3 o'clock.
The part about the scatter I don't know is how the target size is related to the scatter distance. I was going to math it out but I would have had to make too many assumptions and I can't find anything to explain exactly how the mechanics work.
To adjust my calculation for the t34/76:
31.25% chance to penetrate frontal armour.
60% ((100/110).475+(100/320).525) to 67% ((100/110).525+(100/320).475) chance to penetrate side armour.
91% chance to penetrate rear armour.
To adjust my calculation for the t34/85:
43.75% chance to penetrate frontal armour.
70.47% ((140/110).475+(140/320).525) to 73.28% ((140/110).525+(140/320).475) chance to penetrate side armour.
100% chance to penetrate rear armour.
Quick test of 25 samples. T34/76 v Okw Panther side armour. 8% misses, 36% rear penetrations, 12% frontal penetrations and 44% hits that did not penetrate. This falls in line with my projections and can be confirmed by a much larger sample size.
Because of the way that scatter tables would work, if your tanks front armour isn't exactly 90 degrees of the origin of the shot there is always a possibility of hitting rear armour. I'm sure you've noticed a few "unexplainable" rear armour hits while playing.