Firing Sequence Explained

[ScottVA]

Assuming a bullet is seated into the lands firmly, and a case is properly sized with a .002" shoulder bump, as the bolt closes, the extractor is pushed over and forward of the case rim at battery, I assume. Firing pin strikes primer...what happens next? With the bullet squarely in the lands, does the firing pin still push the case forward until either the extractor stops it or the shoulders contact the chamber OR does primer ignition/powder burning cause the case to expand to the chamber dimension as well as expanding back into the bolt face? I don't see how a firing pin can push a case forward if the bullet is in solid land contact. What about the case of a bullet seated off the lands in the same sized case? Thank you for your help

[Centerfire]

Check out Al Nyhus fine contribution to answer your question. 1/3/2012 General Thanks Al.
Centerrfire

[ScottVA]

Check out Al Nyhus fine contribution to answer your question. 1/3/2012 General Thanks Al.
Centerrfire

Will do. Thanks

[zippy06]

Accurateshooter.com had a really good article, years ago. About the Army trials mid 1980's, High Speed cameras and xray....
My big take away was the bullet stops 3 times before it exits the barrel. 7.62 NATO, 1:10 twist barrel...
Yes. The firing pin does push the case to the head space, which moves the bullet further into the lands.
And the primer comes out of the primer pocket. Depending on load. If it's really hot, when the case head goes rearward. The primer is flattened.
5.56 NATO ammo does this.

Now the old guy that got me into Benchrest. He told me, buy the best equipment, you can afford. So you don't pay twice.
And he told to me, don't worry about the small stuff. You will figure it out.
And to just shoot them.
That was my concern about the bullets, I was making. The point up and such...
We found out at his funeral, he shot the reject bullets he made.
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[ScottVA]

Accurateshooter.com had a really good article, years ago. About the Army trials mid 1980's, High Speed cameras and xray....
My big take away was the bullet stops 3 times before it exits the barrel. 7.62 NATO, 1:10 twist barrel...
Yes. The firing pin does push the case to the head space, which moves the bullet further into the lands.
And the primer comes out of the primer pocket. Depending on load. If it's really hot, when the case head goes rearward. The primer is flattened.
5.56 NATO ammo does this.

Now the old guy that got me into Benchrest. He told me, buy the best equipment, you can afford. So you don't pay twice.
And he told to me, don't worry about the small stuff. You will figure it out.
And to just shoot them.
That was my concern about the bullets, I was making. The point up and such...
We found out at his funeral, he shot the reject bullets he made.
[IMG][/IMG]
[IMG][/IMG]

Thank you so much for the reply. I've been around this stuff for some time, and remember Lowell, also. My question is out of curiosity, purely, and not necessarily something to use as a tune criteria change. Does the bullet, upon firing pin impact on the primer, get pushed further into the case or move further into the lands as the case moves forward? Does neck tension play a roll in it? And like you...I do just shoot them, and the target counts the most. I

[rsmithsr]

Thank you so much for the reply. I've been around this stuff for some time, and remember Lowell, also. My question is out of curiosity, purely, and not necessarily something to use as a tune criteria change. Does the bullet, upon firing pin impact on the primer, get pushed further into the case or move further into the lands as the case moves forward? Does neck tension play a roll in it? And like you...I do just shoot them, and the target counts the most. I

firing pin springs are in the mid 20's and competition neck tension is not much, the answer is likely the bullet seats deeper, jamming a copper bullet further into the lands would depend on how shallow the throat angle is....maybe the case shortens on fp impact