Is there any work that has gone into transonic slug stability? This is a valid question, imo, because of the low-recoil slugs available to LE, today. They begin with a velocity barely over the speed of sound, and by 75 yards have gone fully subsonic. At 35-50 yards, they are passing through the transonic zone, which as we know can be a real havoc causer with rifle rounds. We care enough about slug accuracy to buy things and design things like the "Truball" slugs, etc.
Is the foster slug agnostic to the transonic barrier, or does it cause a measurable accuracy issue?