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Thread: bullet setback in case

  1. #11
    Join Date
    25th September 2006
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    South of Lake Superior
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    I see the two images in the previous post have now gone into the Photobucket graveyard. I'll periodically try to add them, starting right now. . . .

    [Rats! No luck now - maybe later - maybe never!]





    I'll be a monkey's uncle - they popped up without me doing anything! And they're back in the previous post too!! Wonder how long they'll be visible?
    When you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind. [Lord Kelvin]
    Last edited by niemi24s; 25th October 2018 at 20:15.


  2. #12
    Join Date
    2nd December 2004
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    You are over analyzing the problem.
    My straight stick magazine guns set back.
    Like my Thomson did.

    A 1911 is a controlled feed handgun.
    The case rim is captured by the extractor under spring pressure.

    You are NOT correctly considering ALL the forces involved.

    The rim slides up the breech face and is held by spring tension from the extractor against the left side of the slide.

  3. #13
    Join Date
    25th September 2006
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    Quote Originally Posted by brickeyee View Post
    You are over analyzing the problem.
    You, however, are incorrectly analyzing the problem.
    My straight stick magazine guns set back. Like my Thomson did.
    This has no bearing on the matter at hand.
    A 1911 is a controlled feed handgun.
    It certainly is, but ......
    The case rim is captured by the extractor under spring pressure. You are NOT correctly considering ALL the forces involved. The rim slides up the breech face and is held by spring tension from the extractor against the left side of the slide.
    This has precisely nothing to do do with bullet setback. Nothing.

    You have failed to comprehend that all the stuff mentioned in Post #2 that most contribute to bullet setback occurs before the cartridge is even released from the magazine.

    • The case rim has not yet been released by the magazine feed lips - especially for the first few rounds from a full magazine.
    • Because the case rim is still under the control of the magazine feed lips, the extractor is not anywhere near the case rim even though the case head is against the breech face.
    • At this point a nosediving round will have its bullet against the feed ramp and its case rim still under the control of the magazine feed lips

    Do yourself a favor and get familiar with how the 1911 really works by seeing for yourself and not relying on the mantra of others. F'rinstance, set your gun up like this and lay your Orphan Annies on it:

    http://

    Q: How much involvement does the extractor have in bullet setback when a nosediving round first contacts the frame feed ramp?
    When you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind. [Lord Kelvin]
    Last edited by niemi24s; 29th October 2018 at 22:42.


  4. #14
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    If anybody wants to experiment to see what conditions cause the most bullet setback, I'd recommend using CCI Blazer (aluminum or brass cased). That's because it suffered the most setback of all the commercial 45 Auto ammunition I've used during my extensive setback testing (see first image in Post #4). That alone makes it the best round for testing. In addition:

    • Make the test gun safe by removing its firing pin and replacing the FPS with a dummy FPS threaded to accept an eyebolt that goes into the firing pin tunnel far enough to hold the dummy FPS in place:

    http://

    • Slingshot the slide by holding the gun about a foot from your chest while firmly pinching the eyebolt. Then thrust the gun forward explosively and violently while at the same time jerking back on the eyebolt so the eyebolt is jerked from your grasp and and slide is freed to go to battery. This seems the best imitation of live firing.
    • To see where the cartridge being slingshotted makes contact on its way into the chamber, I coat the frame and barrel ramps with a layer of soot from a candle or a butane lighter. I found it the best indicator as it comes off easily making the contact point(s) easy to see, as shown below.

    http://

    • Take notes on everything: recoil spring weight; test round COAL before and after; magazine used; ammunition used; number of rounds in the magazine, etc.
    • Because a chambered round usually makes contact with both the frame ramp and chamber roof while being fed, you can even get adventurous by repeating the tests with the barrel removed from the gun and fabricating something like this to hold what's left of the gun and cushion the bullet to a gentle as possible stop without further setback after frame ramp contact:

    http://

    But don't take my word for any of this stuff. See for yourself.
    When you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind. [Lord Kelvin]
    Last edited by niemi24s; 31st October 2018 at 22:09.


  5. #15
    Join Date
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    Complete and total overkill.
    Adjust your neck tension by reducing the size of your flaring head.
    After many years of Bullseye competition this is overkill.

  6. #16
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    Well, I've only been shooting NRA Bullseye since 1962 and as you can see from the first image in Post #4 (the "my lead loads" entry) I personally don't have a problem with bullet setback. But other folks either do or are curious about it and I just happen to know quite a bit about the subject - what causes it, what contributes to it and how to prevent most of it.

    Call it overkill if you want. I call it a thorough understanding of the subject. Other than that, all I have to add is...... <yawn>

    'Bye
    When you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind. [Lord Kelvin]
    Last edited by niemi24s; 2nd November 2018 at 14:25.


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