Chamber pressure during extraction
I once posted that residual chamber pressure helped power the bolt cycle, and got the impression from posters I could do more to help understand the action cycle if I would not bother. They had all the answers.
While reading a recent edition of the "Book of the AR15," I ran across a reprint of the Guns and Ammo article from November 68 titled "Is the 'new' M16 debugged?"
The author, James Mason, takes the time to describe the action cycle, and I quote "The unlocking action happens so quickly that there is still considerable remaining or residual pressure (10,000 to 12,000 psi) in the breech following the passage of the bullet from the bore. This transient residual pressure helps operate the action by forcing the empty case out of the chamber and assisting the rearward movement of the breechblock and its carrier. (The dependence on residual pressure allows for the reliable use of lighter weight operation parts.)" end of quote.
This article also goes into specific detail about how the action can malfunction and what parts were changed - in the months preceding November 68, the date of it's printing.
I have a concept that the early writers had direct access to Colt engineers and Army technicians, whereas today, that same data is considered proprietary. There's a lot of stuff in that article that relates directly to the same problems carbine actions have.