lockingblock
AH enthusiast
Taper in a case means that primary extraction does 99% of the work. Think...a triangle shaped case, inserted into a triangle shaped chamber. How far back do you have to move it for it to break contact with the case walls? Not far...
Now, compare that to a cylinder shaped case inserted into a cylinder shaped chamber. How far back to you have to move (extract) it for it to break contact with the case walls? Long way...
Throw in a grain of sand between the case wall and the chamber. What happens to each? The will fireform around it, yes? Ok...the triangle fireforms around it and upon primary extraction, is off of it.
The cylinder has to roll it all the way out/back....but that fireform is a ramp shape that wants to wedge that grain of sand between the chamber and the case, much like a wheel chock. Now you can raise the bold handle...but not pull the bolt back.
A good example of this is the 7.62x39 used in the AK 47. It is a tapered case and uber reliable despite being steel cased, corrosively primed, and used in harsh climates. Throw in a chromed chamber and robust extractor and you are good to go.
Now, compare that to a cylinder shaped case inserted into a cylinder shaped chamber. How far back to you have to move (extract) it for it to break contact with the case walls? Long way...
Throw in a grain of sand between the case wall and the chamber. What happens to each? The will fireform around it, yes? Ok...the triangle fireforms around it and upon primary extraction, is off of it.
The cylinder has to roll it all the way out/back....but that fireform is a ramp shape that wants to wedge that grain of sand between the chamber and the case, much like a wheel chock. Now you can raise the bold handle...but not pull the bolt back.
A good example of this is the 7.62x39 used in the AK 47. It is a tapered case and uber reliable despite being steel cased, corrosively primed, and used in harsh climates. Throw in a chromed chamber and robust extractor and you are good to go.
