Weatherby chamberings
still have that freebore.... greater than 19mm in cases! so depending on the specific
chambering, the issue of freebore and seating depth is irrelevant...
Some chamberings have zero freebore, some lots, some freebore is overbore some is underbore, therefore some bullets when leaving the case neck are jumping an air gap being a zone of no-contact, before engaging the rifling, some bullets are swaged down as they hit the 'freebore'.... there are so many combinations its ridiculous to generalise.....
Therefore I'd say for accuracy its most import to be consistent with powder load, consistent with seating position, it will then follow that the velocity will be consistent and the issues with engaging the rifling will also be consistent (chamber pressure ).
There are also variations with rifling leade angle, some are sharp and abrupt, others are ridiculously 'leisurely'.....
Now, dont say I dont do anything for you noobs....If you look at the ol trusty 308 winchester, based on the CIP chamber and cartridge with the addition of the NATO spec M80 ball round, 147 gr projectile, you get something looking like this;
Theres a lot of detail there, so have patience.... but the red is the chamber spec, the blue is the case spec and the green is the NATO spec..... blue has double lines in areas representing the min / max....while the thick red is the rifling.. more to come
.