On the SimHQ tank battles map yesterday, another human player and I both spotted each other about 1200 metres away. At 1000 metres, we started exchanging blows. The zeroing system works really well - it only took two or three shots before I had the range dialed in. We slugged it out for what seemed like a minute or two. At this range, the rounds were not penetrating frontal armour and so no real damage was incurred, which, from my brief research, seems to be realistic. I'm not sure how long we could have gone on like this, but I was eventually flanked by a tank destroyer and killed by it at close range.
But yes, the whole system works very well, and it's a lot of fun.
"...for who are so free as the sons of the waves?"