Cartridge base to ogive question

[Barrys]

I've got the cle 223 match chamber. I notice hornadys measuring tool has the modified case and that sinclairs tool says to use a fired cartidge. So- my question is wouldn't the the ideal thing to use be your own cartridge that has been fired AND shoulder sized/bumped back to ones personal preference before trying to take a cartridge base to ogive measurement? So- i would first fire some rounds, then measure and take the average minimum measurement of shoulder movement, subtract say 3 thousandths, resize fired cases to -.003 and then use shoulder bumped case to take my base to ogive . Or does it not matter?

 

[Texas Solo]

I don't think it would matter. When looking for a COAL, you're looking at a measure of length, not chamber dimensions.
The length from your bolt face to the ogive would be the same, regardless of the brass used.

 

[Barrys]

Thank you.

 

[243winxb]

Modified cases http://www.brownells.com/.aspx/lid=12897/GunTechdetail/Gauging_Success___Minimum_Headspace_and_Maximum_COL

I realized the modified case is pushed against the chamber shoulder to get O.A.L readings, so headspace variations are relatively meaningless.

If the case is pushed forward till its stopped by the shoulder, you dont get a head to ogive measurement that is correct. Unless the case is fire formed to the chamber. Just how i am looking at it. :-\ But keep in mind, the firing pin strike may set the shoulder back .006" on firing. ;D

 

[CovertGunny]

I have a continuation question on this topic. I have a Sinclair seating depth tool, what I don't like is that the directions say measure from base bullet to tip and add it to whatever you get from the depth tool with chambering your cartridge. Wouldn't it be ideal to have a comparator say from Stoney to get the base to ogive measurement of the bullet instead. Considering the redding seating dies go off that measurement?

 

[Old Navy]

My 6BRX modified case and twice fired cases are within .001" from base to datum line. If you barrel was properly chambered you should have similar results. Later! Frank

 

['Freak]

Mostly repeating a reply to another but similar:
I get a better, more consistent feel for what’s going on using the Sinclair tool rod held directly against the base of the bullet, not having to deal with shoving through a modified case. The first stop you set indicates base of that bullet with ogive touching and then the second stop is set to the head of any case, preferably one that’s been fully fire formed to that chamber. Add bullet base to ogive dimension from your comparator to the dimension you get from the tool between the two stops and you have the case head to ogive dimension for seating a dummy round.