HerrTom

In the wild.

There's a definite limit.  I put together 150 frames.... and it didn't work
Had a beautiful animation ready.  Still is below:

Animation: https://i.imgur.com/sXZkHVK.gifv
Screenshots are below.  I had to cull the 150 frames to 25, which I think is the maximum.

The above I think is my favourite...  Great look, methinks.

In action.

Autocannon fire.
And a quick video of mortars. The animation runs a little too fast now, I think...
Clearly my next step is to take a look at the smoke bitmaps and bring them in line.
And...
@Battlefront.com I'm guessing it's 100% unlikely to be added - but I'd love the ability to create arbitrarily long animations using your system... 
That and tagging for explosions - like explosiona001[metal].bmp or something for when something strikes metal - like a tasty tank and explosiona001[dirt].bmp for dirt, etc...

Iron mode rulzzz!  Other modes droolzzz!  

Turn save files are huge because they are separate - replays would get rid of most of the redundant data (no need to write every thing all over again each minute). Plus we have Total War as an example where it saves actions of every single soldier (out of thousands) on the battlefield in really small replay files and you see exactly the same battle when you watch the replay. Also DCS World with its glorious replays.
But yeah yeah I know - it's of course more of a question of dev time and resources on Battlefront's part and whether they can spare them for something like this.
But it's certainly doable with little performance hit (if any)

So, in terms of pure kinetic energy, a monstrous 200kg shell travelling at 1.2 km/s has an energy of 144 megajoules.  That's just (1/2 m u²).  According to Wikipedia, the M829 shell weighs 18.64 kilograms, and has a muzle velocity of 1,670 m/s.  That gives a muzzle energy of 25.74 megajoules. 
If all of that energy is released from the impact, being hit by an M829 at point blank is like having 5 kilograms of TNT go off on the outside of your tank.  That may be hard to miss.  I read that Chobham armour is typically about 5cm thick, which means that the reaction force from the shell decelerating in that thickness is 5.1 giganewtons, which would give a nice jolt, even if it's only applied for a tiny fraction of a second.
 
Anyway, I'm not sure what this all means in terms of a chunk of metal hitting another big chunk of metal/ceramics/composites or whatever.  But those are the numbers.  I do know for sure that I'd rather not be in a tank that's shot by one of these in really any circumstances!