Some thoughts on various throat fits.
GLOVE FIT: taper of bullet matches taper of throat/leade. In theory this is the holy grail of cast bullet fits. It is sometimes successfully used by benchrest shooters, i.e., the Ardito throat. However, I find it is a problematic fit. As any machinist who works with tapered collets knows, the taper-within-a-taper is either locked up solid or else it is loose, there is no in between.
Benchrest shooters get around this problem by having light neck tension, seating the bullet long, and letting the rifle finish seating the bullet as the round chambers. If you then try to extract the unfired round, the bullet is stuck in the throat. Neither the light neck tension nor the stuck bullets are practical for any sort of real life shooting.
BULLET TAPER LESS THAN THROAT TAPER: this is what I attempted to do with my 35 caliber 0.8 degree taper bullet in a 1 degree taper throat. The slight mis-match ensures that the front band will be the first to make contact with the rifling.
BULLET TAPER GREATER THAN THROAT TAPER: this ensures that the first full diameter band will be the first to make contact with the throat, while the tapered bands will not make contact.
2-DIAMETER (BORE RIDING): If the throat angle is steep, as is common on many SAAMI chambers, the bore rider will probably be first to make contact with the rifling. But if the throat angle is shallow, the front band may make contact with the throat before the bore rider makes contact with the rifling.
FREEBORE: if the rifle has a long freebore, it may be better to have a one diameter bullet to fit the freebore, snuggling up to the rifling, and not worry so much about fitting the leade. I've heard that Veral Smith prefers this type of throat?
If the freebore is so long that it is not possible to snuggle the bullet against the rifling -- typical on many dangerous game rifles -- you may actually have better luck with a 2-diameter bullet, even though the bullet will have to jump farther to contact the rifling. This seems contradictory, but it may be that the 2-diameter bullet distorts less when it slams into the rifling.
I consider myself a student of this subject, still learning stuff every day. There is no substitute for trying different things and seeing what works or what doesn't work. Conventional wisdom is sometimes wrong -- for example, I've found that it's a royal pain to achieve a consistent fit with "glove fit" bullets, and they don't necessarily shoot any better than other types of fits. I'm still in search of the perfect bullet and throat combination.