Roskoe
The last sabot I chrono'edgoing across mine was traveling at 760 feet per second. at 12' feet that would bruise a guy or break the face plate of a chrono. Often I shoot across the chrono without the sky screens if there is enough clouds and often i do not get the bullet speed but I do get the sabot speed.
So far I have really been lucky as my sabot are getting across the chrono, but if the crown of the barrel happens to be dinged a bit or the wind is blowing right you might really get some strange acting sabots.