[quote 

Dr Mann recorded the path of the bullet that was not co-axial with the bore (tilted).  It moved down range (IFRC) in a spiral.  Orienting it helped the group size by moving the group postion from random to one place or another around the clock.

[/quote]

Over the years I have read some stuff from well respected HP and LR shooters who believe all bullets spiral as they travel from muzzle to target. Their work is done with swaged bullets which should be free of internal defects and as round as the swage die can make them.

I have used lathe-bored AND cherry-cut moulds (custom and factory both). I believe the bottom line is the level of quality control maintained in either method. I have used moulds from Steve Brooks (lathe) and Dave Mos (cherry) and have seen no real discernible difference between them in QC or in shooting. Brooks lathe boring lends itself to more flexibility in body dia., groove width/length, etc. In either case, when tooling is worn, replace it!

I agree with Jim about what happens to a bullet in the bore while under many thousands of pounds of pressure. I also believe that considering the cost of custom moulds if one of them comes to you more than a thou or two out of round it should go right back in the mail. Out-of-round bullets can result from or be exaserbated by poor casting techniques also.