The 8.15x46R and 32-40 has one basic flaw that we try to work around as reloaders.
None of the cases has parallel necks to properly steer/guide the buppet into the rifling.
The next best thing is to have the bullet nose touch the rifling/forcing cone.
That way it is centered at the nose and in/by the case.
I have 1 Accurate mould that is .317" at the nose for short brass. It will touch the rifling and shoots better than my eyes can.
I had another Accurate made with a .300" boreriding nose that i use in full length resized 30-30 brass. No load development as of yet.
The reason is that my rifle has no throat but the neck diameter continues directly into the rifling, being @ .495" long. (in fact it will chamber a 32-40 loaded round!)
As a general rule boreriders are a "bad" thing in as they are notorisly difficult to design and get to shoot good.
The nose has to be large enough that it lightly engraves the rifling but small enough that a bullet cast a little big should still enter the rifling without excessive force.
A borerider cast "small" will essentially be free floating the long nose in the rifling without support. No good.
(You need to Login or Register to view media files and links) Here is the bullet with the "big" nose just grasing the rifling
(You need to Login or Register to view media files and links)