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Thread: Chamber and throat relationship.

  1. #1
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    Chamber and throat relationship.

    After talking to a friend, I realized he was having trouble visualizing the relationship of the chamber, throat and the loaded cartridge so I decided to try to give some folks a visual.

    Below is a cut-away of a 30-06 chamber, an empty case and a 311291 boolit. Notice the highlighted red area is the "throat."



    Below is the empty case sitting in the cut-away chamber.



    Below is a checked, sized, and lubed 311291 boolit in the throat.



    Next, the assembled dummy starting into the throat.



    Next is the assembled dummy pushed into its fully seated position. Sorry... still a little fuzzy.



    Lastly, note the end of the throat is indicated by the light red line in the flat above the chamber and how the entire throat is nearly filled by the boolit.



    I hope this helps some fellows to understand what we are talking about when we talk about "filling the throat."

    BTW, notice the chamber cut-away has an area highlighted with red marker (in the first picture), commonly called the "throat."

    Edd

    P.S....I tried to get a couple pictures of better quality but still have one that is a little fuzzy. Hope you can still get the picture...pun intended!

    2/6/15: I was able to find the pictures on an old hardrive and up loaded them into my Photobucket account. Apparently Photobucket has some issues and my original links went dead. Hopefully everyone can make use of the stickie in its restored state.
    Last edited by badgeredd; 02-06-2015 at 10:53 AM. Reason: Picture found and re-inserted.
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    Thanks for sharing. Sticky?


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    Boolit Master

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    that is worth the thousand words!!!

    Thank you for sharing.

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    very nice!
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    Quote Originally Posted by blikseme300 View Post
    Thanks for sharing. Sticky?

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    Well if I was a better photographer, it would be a bit better, but I seem to have gotten the point across. I sincerely hope it helps those among us that benefit from visual images. Thanks guys for the comments.

    Edd
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    Awesome, nice to see a visual. Now whats the difference between throat and "freebore", so I've heard it mentioned before.
    I really hate to ask this but where does the rifling start in the top pic?

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    Quote Originally Posted by Lefty SRH View Post
    Awesome, nice to see a visual. Now whats the difference between throat and "freebore", so I've heard it mentioned before.
    I really hate to ask this but where does the rifling start in the top pic?
    The area often called freebore is part of the throat as is the leade. Freebore to my understanding is the length a bullet has to jump before the bullet starts to engage the rifling. I'm sure someone else may explain it more correctly than I.

    The rifling in the chamber above starts at the end of the red highlighted area away from the case in the top above picture (the first one). Clear as mud?

    Edd
    Last edited by badgeredd; 10-19-2012 at 09:55 AM.
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    Steve,

    If you click on the link to the album, you can enlarge the picture a bit and actually see some of the rifling in the left end of the chamber cut-away. Like I said above, the throat ends basically where the rifling begins or at the end of the red area.

    Edd
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    Beware of man who types much, but says nothing.

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    Quote Originally Posted by badgeredd View Post
    Steve,

    If you click on the link to the album, you can enlarge the picture a bit and actually see some of the rifling in the left end of the chamber cut-away. Like I said above, the throat ends basically where the rifling begins or at the end of the red area.

    Edd
    So if "freebore" is the lead to the rifling then am I correct by saying this chamber doesn't have any "freebore" since it goes from throat straight to rifling?

  11. #11
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    OK...perhaps this will help.

    http://www.bellmtcs.com/FAQ/ChamberThroats101.htm

    Use the pictures to kinda reference the parts of the throat that are mentioned in the article at the link.

    Edd
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    Beware of man who types much, but says nothing.

  12. #12
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    Quote Originally Posted by Lefty SRH View Post
    So if "freebore" is the lead to the rifling then am I correct by saying this chamber doesn't have any "freebore" since it goes from throat straight to rifling?
    The boolit is seated out eliminating freebore. IF, it was seated to the crimp groove then the portion exposed would be the free bore.

    The chamber has freebore but the fit of the boolit eliminates its existence.
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    Boolit Master crabo's Avatar
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    Alright! I have milled out my chamber like you did. What do I do next to get good boolit fit??
    Crabo

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  14. #14
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    Quote Originally Posted by crabo View Post
    Alright! I have milled out my chamber like you did. What do I do next to get good boolit fit??


    Funny guy you are. I 'spect you'll see pressure problems very early in your research.

    Edd
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    "The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in Government." -- Thomas Jefferson

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    Beware of man who types much, but says nothing.

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    If you hold the "Ctrl" key down the image can be scrolled larger or smaller using the Mouse! (A trick I learned right here on this site!!!)
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    I decided to stick this before I got through Edd's pictures. Great write up.
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  17. #17
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    Very interesting. Would this weapon only then shoot this shape boolit>?

  18. #18
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    Quote Originally Posted by _Hawkeye_ View Post
    Very interesting. Would this weapon only then shoot this shape boolit>?
    No, the chamber/cartridge combo is not limited to this particular boolit. I used this particular boolit because a) it was readily available and b) it pretty much demonstrated what I wanted to show.

    The idea is to fill the throat as much as possible with a boolit regardless of its shape. If the boolit shape doesn't lend itself to mostly filling the throat, one cannot expect good results. A person MAY be pleasantly surprised, but the likelihood of a boolit working well and not at least mostly filling the throat is not in one's favor.

    Edd
    Charter member Michigan liars club!

    "The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in Government." -- Thomas Jefferson

    "Consider the clown(s) just one of God's little nettles in the woods, don't let it detract from the beauty. Sooner or latter you are going to run into the nettles regardless of how careful you are."

    Beware of man who types much, but says nothing.

  19. #19
    Boolit Master 303Guy's Avatar
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    Great thread, badgeredd.
    That's such an informative set of photo's - thanks!

    In fact, those photo's are so valuable in my opinion that I feel obliged to ask that you beg steel or borrow a high resolution camera for these photo's.

    Good one, crabo. Someone had to say it!
    Last edited by 303Guy; 11-07-2012 at 03:55 AM.
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    Thank you for the Great pictures! I learn something everyday on this site.
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