Freebore… how do you measure it?

[Intheshop]

That was a "shorty",here's what most folks call a bore rider.

Look at the shiny part on the nose;

That is a taper created by swaging into a very simple die. The taper's location,or distance to body's shoulder, is adjusted to set the loaded bullet base height, within the case. You just have to run some groups to see where it tunes the best.

 

[chop house]

I tried seating a bullet in the case backwards and got measurement of .165 on a .104 freebore. You just told me why. That .244 or .245 makes a difference.

in addition, at the risk of invoking a 'guffeyism', using a backwards bullet will overstate freebore due to the bevel on the base of the bullet. on the following example of 6mm bullet, calculations would add approx 0.015 to the 'apparent' freebore:





as guffey would say.... "my datums are sharp. they will leave a mark". hence the use of pin gauges.