Alan,
The term "bore" means the diameter at the tops of the rifling "lands" in a barrel.
The term "groove" is the diameter at the bottoms of the rifling's grooves in a barrel.
A bore riding cast bullet typically has the forward portion or nose at the "bore diameter dimension". Thus this rides on the tops of the lands of the rifling while the bearing surface or rear portion is sized to "groove" or the larger diameter of the barrel.
The idea of a bore riding bullet is the nose acting as a type of "pilot" to guide the bullet down the barrel by giving it this crucial nose support.
Sometimes a custom mold has to be used to arrive at the proper bullet nose diameter and sometimes a special sizing die is employed to do this also.
FWIW
The term "bore" means the diameter at the tops of the rifling "lands" in a barrel.
The term "groove" is the diameter at the bottoms of the rifling's grooves in a barrel.
A bore riding cast bullet typically has the forward portion or nose at the "bore diameter dimension". Thus this rides on the tops of the lands of the rifling while the bearing surface or rear portion is sized to "groove" or the larger diameter of the barrel.
The idea of a bore riding bullet is the nose acting as a type of "pilot" to guide the bullet down the barrel by giving it this crucial nose support.
Sometimes a custom mold has to be used to arrive at the proper bullet nose diameter and sometimes a special sizing die is employed to do this also.
FWIW
