The problem with saboting is that the rifling in a barrel is typically selected for a bullet of a specific weight to acheive maximum stability and accuracy. A .223 is typically rifled with one complete twist every 9 inches, called 1 X 9, while a .30 caliber barrel is typically rifled with a 1 X 12 twist rate. Doesn't the velocity figure into that too? If the velocity were 1/3 faster with the sabot round, the bullet spin rate, in terms of revolutions per second, rather than revolutions per foot of forward motion, be the the same as the slower round fired from the 1 in 9 twist barrel.
Yes, velocity does. But there is a reason that the serious precision shooters don't use them; they are not as accurate as a full bore diameter bullet.