Mark Bradshaw asked me to review this thread and comment.
I will start out assuming the thread was about semi-autos, though the relevance to revolvers, at each step, will be obvious.
The cartridge has two functions: (1) to position the bullet in front of the freebore, more or less centered on the freebore/barrel axis; and (2) to propel the bullet into the freebore.
The freebore has two functions:
(1) to align the axis of the bullet with the axis of the barrel prior to engraving the bullet in the rifling (ideally, the freebore would only be about 0.001 inch larger than the bullet and about as long as the length of the bearing band on the bullet); and
(2) in IPSC major to give the bullet some distance to get up to speed before it begins to engrave in the rifling (this lowers peak pressure by increasing the volume behind the bullet, before the bullet encounters the resistance related to engraving, and peak pressure is reached).
The angle at which the lands engrave the bullet is a primary determinant of accuracy. If you make a table of rifle cartridges, listing them from least accurate to most accurate, and then place the land angle specified in that cartridge's specification adjacent each cartridge entry, you will find that the shallower the land angle the better the cartridge's accuracy. This shouldn't be a surprise, as a less abrupt engraving process is more likely to occur reproducibly.
Revolvers have the additional problem of transporting the bullet from the cartridge to the freebore and I suspect that if: (1) the cylinder alignment is more accurate; (2) the cylinder hole diameter forward of the cartridge is barely bigger than the bullet diameter; and (3) whatever forcing cone moves the bullet into alignment with the freebore does so more gently, then the revolver will produce better accuracy.
So, if Taylor recommended a tighter longer freebore and a shallow land angle for engraving, he was doing exactly what one should do to improve accuracy.
Wil Schuemann
