Some may regard this as going backwards, but interesting none the less. Loading down centrefires with airgun pellets to airgun velocities. Shows .17, .20, .22, .25 and .357's loaded.
http://www.youtube.com/watch?v=LURS89_O1JU
This has been a known practice, but I've never seen it covered over such a range of calibers with chrony'd results..