the extractor will spring around the head of the shell casing
I believe what you are trying to say is "the extractor will spring around the head rim of the shell casing "...But you're wrong.... The extractor cannot "spring around" the rim of a cartridge because the tolerance inside the receiver are too tight to allow the extractor to "spring around" the rim of the cartridge.
The extractor covers about 1/4 of the circumference of the face of the bolt, and the annular slot that grabs the rim of the cartridge covers about 1/2 of the circumference of the bolt face which leaves about 1/4 of the face of the bolt open to accept the cartridge as the cartridge is fed into the bolt by the spring in the magazine pushing the cartridge up and into the bolt.
No I meant the head of the cartridge. You obviously knew what was being discussed. Call it what you may, extractor groove, base of the cartridge, head, or rim take your pick it is all the same.
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"But you're wrong.... The extractor cannot "spring around" the rim of a cartridge because the tolerance inside the receiver are too tight to allow the extractor to "spring around" the rim of the cartridge."
But yet it does work that way. Absolute nonsense stating it doesn't. Stop pretending and buy a rifle and go shoot it. You will then know what the rest of us know. I bet it is hard to give up a concept you have been railing at for years.
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Just like Frazier, here is one more firearms expert describing how the extractor springs around the head of the cartridge when the shell is already present in the chamber.
Joseph Nicol stating in his WC testimony about the extractor springing around the head of the shell, obviously also felt it was possible in answering a question from Eisenberg.
Mr. EISENBERG. Now, what led you to the conclusion that this was an ex tractor mark?
Mr. NICOL. Only that it appears at the location of the cartridge case where an extractor mark would normally be found. That is to say, this would be the mark where the extractor strikes the edge of the case,
and then springs around as the cartridge is driven into the chamber.