Because the software code for drawing the bullet on the design program is complicated, I cut a few corners here and there to simplify the code. The simplifications are small features that you usually would not be able to discern on the drawing, anyway. One of those small features is the transition between the front band and the nose on a bore riding bullet, or on a Keith bullet.
A typical example below. The drawing pretends there is a 90 degree corner between the front band and the bore riding nose, but in true life the mold will have a 45 degree transition there (65 degrees on my Keith molds). The resolution of the bullet drawing is such that you often can't discern that detail, so why worry about it, right?
Unless ... you are an Elmer Keith fan, in which case you may believe that it's a matter of life and death to have square corners rather than angled transitions. Elmer was a simple man with some simple ideas and the square corner thing was one of those simple ideas that he latched onto and preached to his followers. I believe Elmer was either mistaken or misinterpreted, but he's dead so I can't have that discussion with him.
The truth is that very few molds have 90 degree corners, nor should they. An angled or curved transition makes it easier for molten lead to flow around the corner, and easier for the bullet to release from the mold. This 1981 Lyman blueprint of a 358429 calls out an angled transition between the front band and the ogive.
On the other hand, this 1981 Lyman blueprint of a 429421 seems to show a 90 degree corner between the front band and the ogive, though that feature is not actually specified anywhere, and every photo of a 429421 mold that I can find on short notice shows an angle there -- a steep angle, perhaps 70 - 80 degrees, but an angle nonetheless. I'm guessing Lyman's drawing shows a 90 degree corner for the same reason my bullet drawings have shown a 90 degree corner -- to simplify the drawing.
An Ideal 429421 on the right (photo from a Glen Fryxell article). If you look closely there's a bit of an angled transition between the front band and the ogive. It's not 90 degrees, nor should it be.
Did the mold makers bastardize Elmer's design, as Elmer seemed to suggest? Maybe, but it's not clear how Elmer communicated his design specifications to the mold makers in the first place. As far as I know Elmer never produced a blueprint or even a sketch of his designs, and from what I gather, he did not have the skills to produce a blueprint.
I heard a story somewhere -- I don't know if it is true -- that Elmer enlisted the assistance of a machinist friend in Salmon, Idaho, to make some steel "master slugs" for his bullet designs, and that those "master slugs" are what Elmer gave to the mold makers, rather than a drawing. One version of the story has it that somehow the master slugs eventually found their way into Veral Smith's possession -- I don't know if that is true, either, you'd have to ask Veral.
Do square corners shoot better or kill deer better than angled corners? Not that I am aware of. Yet Elmer said square corners are good so it must be true, according to his fans.
At any rate, a customer recently complained because my design page showed what appeared to be 90 degree transition between the front band and the bore riding nose, yet in true life his mold had an angled transition there. I believe the angled transition is a good thing, but I can understand why the customer felt deceived by the drawing, so I plan to add that particular detail to the drawing code in the next few days.