223 AI CBTO

[Gary O'Neal]

To you 223 AI shooters, how are you measuring your CBTO? Are you modifying your own cases? I’m stumped.

 

[SecondsCount]

The Sinclair tool works well

 

[Gary O'Neal]

Thanks so much. I have been reloading since 1972 and I have to say, this is one gadget I’ve never seen before.

 

[SecondsCount]

Thanks so much. I have been reloading since 1972 and I have to say, this is one gadget I’ve never seen before.

Not a problem.

I have to give credit to @lb-ft for showing me that tool.

 

[B23]

I gave a piece of fireformed brass to my smith to drill and tap. For every rifle I have I use a piece of brass shot in that gun to make my modified case for the Hornady tool. The off the shelf store bought cases tend to be a little undersized, probably so they fit in everyone's chamber, and they don't always fit snug which doesn't lend itself to the most accurate and consistent measurements. Drilling and tapping a piece of brass that has been fired in that specific rifle results in a perfect fit.

Alex Wheeler, maybe others have one too, has a good video on how he finds the lands. His way doesn't use any special tools just a case and the bullet.

Go to the link below and his video of finding the lands is down at the bottom of the page.

Videos | wheeleraccuracy

www.wheeleraccuracy.com

 

[Oso]

I started to write a response on the other thread to your question. Glad I looked around before sending.

Just remember that you'll want to fire the case preferably 3 times so that it closely matches your chamber.

 

[urbanrifleman]

To you 223 AI shooters, how are you measuring your CBTO? Are you modifying your own cases? I’m stumped.

Split neck case.

Been doing it this way for 30 years. It costs nothing but a case.

And you can see the pressure ring location.

 

[Coyotefurharvester]

CBTO(cartridge base to ogive) is different than the max cartridge overall length(col, or coal) that the Sinclair tool measures.

 

[jepp2]

how are you measuring your CBTO? Are you modifying your own cases?

I use a better material version of the Sinclair tool. I start by measuring my bullet length, use it with the Sinclair type tool to get cartridge overall length to touch (not jam, not hard jam, etc). Then I seat the bullet and then measure CBTO with the Forster datum dial system to record my number going forward.

I wasn't very accurate Hornady system, the Wheeler method, and I will put my method accuracy against any other suggested method. But in reality, any of the suggested methods will give you all you need to have a reference to work from.

And although I haven't changed my starting point, I have strongly considered my initial loads being a hard jam (like 0.020" in the lands) so everything is lower pressure as you work your bullet seating depth to shorter CBTO.