please explain free bore in chambers and on reamers

[Ogre6br]

HI
Can you guys please explain free bore in chambers and on reamers.

Was talking to a G-smith and his 30 BR reamer is a "No freebore" reamer.

What does no freebore mean?
Does the chamber finish in a sharp angle and the rifling start straight away or is there still a blending of chamber and rifling?
Is free bore and leade the same thing??

I am trying to work out a beginning seating depth and have got 2 projectiles,
one a FBHP and one a HPBT that are similar weight.
I am trying to seat everything a minimum of 50 thou above the neck shoulder join area to avoid the doughnut formed when expanding the necks up with a tapered expander from 6mm to .30 cal. I am doing this as I dont have anyway of removing the doughnut inside the necks and I dont want the pressure problems associated with projectiles in the doughnut area.

THanks

later
p

 

[ronemus]

Freebore is a cylindrical section slightly over bullet diameter between the case neck and the rifling. The leade is the tapered region from the start of the rifling at zero depth to full rifling depth. With no freebore the leade starts immediately in front of the case neck.