Correct me if I am wrong but a BT bullet is nothing more then an HP bullet with a platic tip filling that hole and giving it a point for coefficiency (sp)

Correct...and because the tip is holllow the center of gravity is moved back which helps make the bullet more accurate...

Yip, Noslter has one poly tipped bullet that they designate as "Varmint" and another poly tipped bullet designated as "Hunting". The Varmint bullet has a much thinner jacket for a more violent/quicker expansion.
As far as that goes, not all hollow points are created equal either. But as was mentioned, in general, the poly tipped bullets are designed for flatter trajectorys with higher bc's.

Ya I know nosler comes in two different configurations, one for varmints and one for medium game, I dont think packaging has anything to do with it though, the smaller calibers are generally for varmints and the bigger for deer. Orange tip= varmints and green tip = deer.
I dont see how the nosler solid is the same, the solid is just that, solid= no lead at all.

You are correct. But the plastic tip changes the way it expands by acting as a wedge......

He posted "solid base"not just "solid".The Nosler "solid base" does have a lead tip.