You are Here:
CBTO curiosity question

Author (Read 27 times)

CBTO curiosity question
« on: February 10, 2019, 11:35:25 AM »
 

madsamurai

  • Target Painter
  • *
  • 1
    Posts
  • Karma: 0
  • FNG
Hi guys... new to reloading in general and especially precision reloading, but I've been doing my research and getting all my ducks in a row before digging in. I understand what's going on with CBTO vs COAL, and why it's important to measure and control distance from the lands, but I'm curious about why that's measured the way it is. My understanding is that the cartridge seats into the chamber and stops against the shoulder (please correct me if that's a misconception), and that after firing, the brass will stretch and lengthen to the bolt face, so fired brass will be longer than new brass. I'm curious then, why we measure from base to ogive rather than from shoulder to ogive, which seems to me would never change. It seems to me like that would be a better way to go, and would allow for the same measurement regardless of whether the brass was new or once fired or more, as compared to the standard CBTO measurement which would need to take that somewhat arbitrary cartridge lengthening into account. Can anyone explain why it's not done that way?
Thanks
 

Re: CBTO curiosity question
« Reply #1 on: February 16, 2019, 02:52:03 PM »
 

NoCall

  • Target Painter
  • *
  • 16
    Posts
  • Karma: 0
  • FNG
You are responsible for sizing the shoulder back to desired length from the the base of the brass. New or fired. Not all brass is created equal. The ogive of the bullet is the first part of the bullet to touch the lands. Nobody really makes a measuring device to go from the shoulder to the ogive of the bullet. So you make every piece of brass the same specs then just measure out to the ogive. Itís not rocket science so there is no need to over think it too much