My best "grass cast" is 128m. Running on the theory that terminal tackle and bait will cost you 30-40% of your distance, I should in favourable conditions be able to get a bait out about 70m.
In reality, favourable conditions (20 knots+ of offshore wind etc) don't occur that often. I'm guessing that most of my actual fishing is done in the 50m zone.
But then, this thread IS about dry land casting and not fishing, the two have little relevance to each other unless you are using one to better the other