Chamber length?

[Tony Williams]

A rather basic question....

In his book on British Small Arms Ammunition 1868-1938, Peter Labbett refers to a .8 inch experimental gun which had a chamber length of 138.4 mm, and a 1 inch with a chamber length of 157.5 mm.

What exactly is the "chamber length"? Is it the same as the cartridge case length, or is it up to the start of the rifling?

 

[reccetrooper]

It should be based on the cartridge case length.
There is the chamber, then the throat, and then the start of the rifling.
Throat lengths can vary for different projectiles and rifling patterns, so if the throat (space between the end of the cartridge case and the start of the rifling) was included in the "chamber length" there would have to be different chamber lengths for the same calibre.

 

[2pounder]

Don't believe case length is the same as chamber length. Why would Peter or his source have used the term and not case length? Also if you look on the rifle ammunition reloading forums they make the point that chamber length should be greater than case length typically by 0.010ins.

 

[reccetrooper]

I wrote my reply badly worded, I meant to answer the original question by saying the chamber is not up to the start of the rifling. It is based around the cartridge dimensions.
SAAMI drawings for rifle calibre chambers are typically +0.015" (0.38mm) longer than the case and +0.002" (0.05mm) greater diameter.

http://saami.org/specifications_and_information/index.cfm

 

[Tony Williams]

Thank you for the clarifications, gentlemen!