Any claim that the 40� shoulder reduces bolt thrust uses imagined "facts" and "logic" that I believe to be unsound. Any claim that reducing the body taper reduces bolt thrust depends on reasoning that I believe to be erroneous.
<br>
<br>By the time the powder gas reaches its peak pressure (assuming at least 50,000 lb/sq in.), the case has long since gripped the chamber wall with its softer neck, shoulder, and forward body, and the increasing pressure beyond that much lower level has already stretched the case enough to press the head of the case HARD against the face of the breech. If I understand these relative pressures -- and the corresponding force against the breech -- correctly, the pressure (thus the force) exerted against the breech is the same with any body taper (given, remember, the same peak pressure).
<br>
<br>Since this theory was introduced many years ago, many have parroted it -- but I've never seen any data that overrode the facts and relationships that argue against it. I'll test it carefully once I determine how best to design the tests properly.
