Originally Posted by
W.R.Buchanan
Look at the Pic. The Crimp is where the Black Line is at the mouth of the case. You can see that it only extends about .015 below the case mouth.
The Area below that on this case measures .423 where the bullet is Seated.
Just below the Base of the Bullet, the case measures .419 which is the product of Full Length Sizing the Case. The whole case was .419 before the bullet was seated.
When the bullet is seated it forces the case open to .423 That is .401 bullet +.011+.011 case wall thickness, which gives this Cartridge a Neck Tension of .002 per side
The top edge of the case where the crimp digs into the boolit measures .417 at the very top edge. This all means that the Crimp intrudes into the bullet .003 all the way around and creates a step on the bullet that prevents Bullet Set Back during Recoil and or Chambering.
Read this, and Re-Read this until you firmly understand it, This is all there is to it.
Hope this helps your understanding of this subject. Sorry about the pic, the site will not allow it to be erected.
Randy