Chamber Specs for Rem 223

[from the Hip]

Gentlemen:
I understand the head space length for a rem 223 chamber is 1.464 -1.473 from the bolt face to the 46deg cone datum. But I fail to understand what the second datum physically is. All I can find is that it is the “chamber cone dia.”. The cone changes dia as it gets longer and is under defined. Is there a better definition of what that 1.464 – 1.473 is in reference to. thanks

 

[Jim Watson]

The headspace datum is a circle of a specific diameter on the shoulder of the chamber. For a .223 that circle is .330" diameter. So the chamber is minimum of 1.464" to where the cone of the shoulder is .330".

 

[from the Hip]

Thank you mr. Watson.