Spindrift, this is my interpretation of a successful nose, based on results. Another successful (and quite versatile) design id the MP 30-180 that you have....that one has angle theta at 1⁰ per side and angle delta at 2.5⁰ which makes for a much steeper taper to the nose. I have a variety of custom .30-caliber moulds covering these ranges and one with a straight taper, and three things I've learned: Parallel is no good except at medium to slow velocity, straight taper is usually no good unless the throat is two parallel sections with an abrupt taper to the ball seat area (a mis-match), and straight bore rider with a throat-matching taper up to the full diameter is almost as bad as a two-diameter Barlow design. Further, if the lube grooves are too shallow and/or the driving bands too wide such that alloy has a difficult time getting moved as the bullet engraves the throat, the body of the bullet can get gas cut, pished crooked, or if the alloy is on the softer side the base can rivet. All of these things cause accuracy-destroying damage to the bullet before it is even fully intobthe barrel.
A bullet with two distinct tapers to the nose gives just the right amount of support to guide into the throat with some "wiggle room" to get there without being deformed. If the body of the bullet is designed correctly it can follow the nose through the throat without requiring so much force that it is mangled in the process. Alloy temper and composition plays hugely into this operation as well, too hard and brittle is a no-no as is too soft and gooey, but what alloy works best is determined by the peak pressure value and pressure curve that the chosen powder is providing.