Alternative to 6.5 Grendel?

[JASmith]

Projectile separation from sabots is inconsistent, so accuracy goes to crap. For close range armor piercing, it's great if you can reach .22-250 velocities.

The inconsistency is probably a result of separating the sabot from a spinning projectile.

Consider the M-1 Abrams tank gun. That is a sabot round and extraordinarily accurate by most of our standards.

Of course it is a smoothbore but one could speculate a scaled down smoothbore might be interesting with respect to the accuracy needs of the average infantryman.

The fly in the ointment may be the length of barrel needed to edge above 3,500 - 4,000 fps.