Ian
Notorious member
The nose is the last part to upset at launch. The force on the base is transferred through the bullet but the compressive force that the inside of the bullet "sees" is less and less going forward toward the nose. Some of the hardest-hitting powder charges I use and softest bullets barely swell the middle of the nose into the grooves. I used to have a different opinion, but since have concluded that nose "slump" from static inertia is a non-factor for cast, if the nose "sets back" during launch it's because of pressure from behind swelling the bullet.
Bumping the nose isn't really gaining you a lot due to the wasp-waist effect, that middle needs to fit too and if it doesn't it will buckle like an arrow does when the clutch is dumped except the arrow will flex itself straight again and the bullet will remain a banana shape. Ever throw a banana? A lot of the inertial deformation can be overcome with slow powder and gentle push (press vs. smack, remember that acceleration is the second derivative of velocity), but as you increase velocity the lack of fit in the middle will show up at a certain point.
Bumping the nose isn't really gaining you a lot due to the wasp-waist effect, that middle needs to fit too and if it doesn't it will buckle like an arrow does when the clutch is dumped except the arrow will flex itself straight again and the bullet will remain a banana shape. Ever throw a banana? A lot of the inertial deformation can be overcome with slow powder and gentle push (press vs. smack, remember that acceleration is the second derivative of velocity), but as you increase velocity the lack of fit in the middle will show up at a certain point.