Why do the Bonded and mono Bullets seem to prefer more jump into the rifling than a standard cup/core bullet. I know it works seating them deeper just not sure why.

Just my swag,the bonded and mono are longer bullets than the cup/core bullets.

I suspect that they are harder and giving them a running start before they're forced into a slightly smaller size while spinning helps keep pressures more uniform from shot to shot.
Thin jacketed cup and lead core can more readily be forced down that small twisted barrel hole.

I'll be happy to hear from somebody that actually knows and isn't just speculating like I am!

It's an odd deal. I haven't seated a mono or Bonded bullet closer than .050 from the rifling in years and seem to end up around .070-.150 with a lot of Bullets. The E-Tips and Scirroco seems to really thrive on the jump.

Every Barnes bullet I've loaded has ended up with the front of the first driving band even with the case mouth, and worked every time. 6x45, 260, 270, 7-08, 7RM, 30-06, 338 WM, 375 H&H.

Just works.

I've heard the same thing from a few folks.

I like this as if the groove part is at the case mouth and it is not crimped I get lint and dirt in there. Probably shouldn't have them loose in my pockets but I doubt I'll change.