case support

Discussion in '1911 Gunsmithing' started by Anderson3754, Nov 10, 2011.

  1. Anderson3754

    Anderson3754 New Member

    49
    Sep 21, 2011
    45 acp case support, 6 o'clock position, standard barrel.

    How does one measure this to ensure that when the pistol goes bang, the case is not pulled back out of the chamber before the bullet has left the barrel ?
     
  2. knedrgr

    knedrgr Low capacity, low tech...

    Aug 15, 2011
    The bullet is already down range before the slide even moves rearward.
     

  3. Anderson3754

    Anderson3754 New Member

    49
    Sep 21, 2011
    I guess I have to disagree a little bit cordially. The bullet is gone and down range before the slide unlocks from the barrel, but upon initial firing the bullet is pulling the barrel forward and the gases are pushing the case up against the breech face with equal pressure. If the pistol has its's headspace on the long side, and the hood length is short, the case is going to be pulled out of the chamber during that nano second. The slide and barrel are still locked together but the case has been pulled out of the chamber, losing case support setting up the 6 o'clock blowout.

    What I'm trying to measure or figure out is how much support is required at 6 o'clock on the case to prevent this.
     
  4. Joe C

    Joe C Custom Pistolsmith Sponsor

    Sep 11, 2011
    Anderson, I have seen hood gaps as big as .021" with a .909" deep chamber with no blowouts...

    Not sure if that helps but it is one example of what I've seen in that area.
     
  5. Anderson3754

    Anderson3754 New Member

    49
    Sep 21, 2011
    Yes that does help. I guess I need to find a better way to explain my question.

    Say for an example we have a barrel that was heavily throated losing approx .010 of case support and the slide is allowed to move rearward .010 during ignition due to the excessive endshake of the short hood length would this .020 the case is pulled out of the chamber be the invitation for the 6 o'oclock blowout.
     
    Last edited: Nov 10, 2011
  6. 50GI-Jess

    50GI-Jess Member

    497
    Aug 24, 2011
    Yes, but at the same time pressure will drop some too. Being a low pressure round, the casing is stronger than most would believe. The only blown out cases I've seen, has been double charges.
    I've been testing way over throated guns with hot loads. Only to find a case bulge now and then. However this practice will eventually weaken the cases, and some may blow up the next time around when reloaded.
    Fortunately the 45 ACP is a very forgiving cartridge, when things starts to get borderline unsafe.
     
  7. Joe C

    Joe C Custom Pistolsmith Sponsor

    Sep 11, 2011
    Well, considering I've seen barrels from some shops over throated by as much as .030-.040" with as much as .010" hood gap that didn't blow out after thousands of rounds, .020" stacked like that wouldn't be that much. Remember, a human hair is approx. .003" thick...so .020" is only 7 hairs...give or take. ;-) but that is just based on my opinions and what I've seen on guns that have come in for repair.

    Now if were talking about a .38super or .40 it would be a different issue in my opinion.
     
  8. Anderson3754

    Anderson3754 New Member

    49
    Sep 21, 2011

    Would you elevate your level of concern on the 45acp if you were using federal cases which probably have the thinnest case support in that web area at +P pressures.
     
  9. Anderson3754

    Anderson3754 New Member

    49
    Sep 21, 2011
    When you say a case bulge from time to time, is it super obvious or an amount you can barely see or measure with the hot loads
     
  10. Joe C

    Joe C Custom Pistolsmith Sponsor

    Sep 11, 2011
    With a gun over throated like I described? Yes. Like you described? Not likely. Look at the Glock as an example. People fire +p loads in them all the time and they are what most would consider over throated...
     
  11. Anderson3754

    Anderson3754 New Member

    49
    Sep 21, 2011
    Yes, never thought about comparing it to the Glock. I appreciate your help again, thankyou.
     
  12. 50GI-Jess

    50GI-Jess Member

    497
    Aug 24, 2011
    @Anderson3754
    Conserning bulged cases ! Even if it is not clearly visible, the cases may bulge some without correct support. Just use calibers and see how the cases may be affected. Like Joe C said, the Glock is a perfect testament and example on how forgiving the 45ACP really is.
    Now +P cases may suffer a shorter life span when used in Glock, but not as much as 40 S&W's, which is a high pressure cartridge.
    Long story short ! Just shoot a lot of 45ACP and make sure your loads are safe. Enjoy.
     
  13. Anderson3754

    Anderson3754 New Member

    49
    Sep 21, 2011

    Good, great, thanks for helping
     

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