Sabot answer, 44cal 300XTP
If anyone else shoots the 300 XTP's in 44 cal "off the shelf" in the 20 per box, likes them, and wants to order quantity, the sabots they come with are 19.248mm tall and need to be ordered from Hornady. It turns out the 44 cal sabots I ordered which are longer/taller came from MMP. There is a definite performance difference from my barrel.