No joke—rimfire BCs?

What DFoo said^^^^
Just remember, NOTHING trumps actual verified field dope. Don't just get out a calculator and dial in to fling a bullet at 250yds, you might get lucky but chances are you will need a good spotter for that first shot,THEN dial in for the gold.
 
On a slightly different note. When I recorded my charts in 10 yard increments to 200 yards, they seem to hold good over a broad range of temps etc. Wind is the big issue. I was a bit surprised how little temp effect I get from 25-90 deg. I suppose it is due to the relatively short range. I also shoot center fires over a much broader temp range, which has more effect, of course.