I picked this off on the discussion of free bore. I need to chew on it as well. Seems to be someone who knows his stuff and does the work

"
Obviously you know something about chambering and I just wanted to share my experiences having also shot completion at the state and national level and also built lots of rifles for myself and others.

The reason that I don't recommend chambers that have a tight neck is they can cause higher pressures without velocities reaching the desired/possible levels if the necks are not turned.

I like to keep the necks as thick as possible as long as they are true and uniform.

No throat is another way to limit the possible velocity of a cartridge. If you short throat a chamber
you will not be able to reach designed velocities without excessive pressure.

The 6.5 x 47 is not a large capacity case and needs the free bore to achieve the designed velocities
for a given bullet weight.

I re chambered a 6.5 x 47 for a friend that had pressure issues with minimum loads and extraction was very hard. after taking a chamber cast to see if I could figure out what the problem was and
discovered it had no throat and a tight neck (Turning the necks would not have solved the problem)

This was a pre-chambered and threaded barrel and it was for a savage and my friend installed it himself. (The head space was correct when I checked it).

I have seen this problem on other rifles with no free bore and tight necks.

Some think that you have to seat the bullet against the lands to get accuracy, with the better dies
chamber reamers and powders we have today this is no longer true.

I personally have 5 rifles and one pistol that will shoot under 1/10th of a minute and they all have
free bore and SAMMI neck diameters.

All of the "New" high velocity/pressure cartridges have Plenty of free bore in order to reach there intended velocities.

I just thought I would explain the reasons for my recommendations.

I hope you don't have any problems and good luck on your build, you will like the 6,5x47."