Freebore… how do you measure it?

[urbanrifleman]

That is A method…….

This is the BEST method for finding "touch". And it works even if the barrel is out of the action. When I set freebores with a throating reamer I can push the case in with my finger and get perfectly accurate repeating measurements.

 

[Dusty Stevens]

That's the "I'm only going to stick in the tip" method.

Just da tip. David allen coe had a song about that.

 

[Intheshop]

"Just the tip",bwahaha

Although this one is a *shorty,Lee 55g in a stupid accurate 223 ADL..... freebore is,or should be the second measure on dialing in "bore ride" cast. The first is actual chamber neck #'s. Chamber prints are fine,to read and get an idea but....

I measure chamber neck before any loading gets done. Using a square bttm,small hole gage,that's assembled into an aluminum arrow,slides in assembled rig. Then after deciding what your loaded case neck clearance..... we have 2 options here. Change bullet diameter,and/or turning necks. Experience plays a big role in this dimensioning and has many factors.

On a typical bore ride;

We get to change the "nose" diameter,independent of bullet's body. If you look at the pic below,notice not only the land engraving but also at the start of the body. You'll see the end of the freebore. How you measure this is going to depend on the diameter of the bullet but.... "usually" we're running snug on the freebore diameter so it takes that little problem out of the equation.

 

[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.