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Thread: Is this what over pressure looks like?

  1. #1
    Boolit Man
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    Is this what over pressure looks like?

    Had a chance to head to the range today and had trouble getting one of my loads to eject after firing.Click image for larger version. 

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    Click image for larger version. 

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    20ga ithaca model 37 rifled
    Fiocchi 2.75
    616 primer
    21gr longshot
    OB20 gas seal
    560gr fullbore (.6185)
    Fold crimp

    Accuracy wasn't good but recoil and muzzle blast all seemed normal.

    Any thoughts?

  2. #2
    Boolit Man
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    The bulges formed where the slot for the extractor is in the chamber. Hence the trouble ejecting. I was able to pry it out pretty easily with a pocket knife.

  3. #3
    Boolit Master
    swheeler's Avatar
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    Yes, I would say over pressure with the brass head flowing behind the extractor like that. Hard to open the slide I'd bet
    Hell, I was there!

  4. #4
    Vendor Sponsor uncle dino's Avatar
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    Yup...d

  5. #5
    Boolit Master
    runfiverun's Avatar
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    definitely over.
    you are pushing over 1-1/4 oz's of lead.
    it's all an educated guess,,,, till the trigger is pulled.

    this opinion brought to you by mister low-tech solution..

  6. #6
    Boolit Buddy
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    fiocchi hulls are not suited for full blown loads. try federal.

  7. #7
    Boolit Man TonyfromItaly's Avatar
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    Hello, small base hulls are not suited for pressure over 750 bars. Better the high brassed ones. However from the markings on the hulls i would say you are over 1000 bars. (14500 psi)

  8. #8
    Boolit Master



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    http://whitetail.winchester.com/2015...shotshellswhy/

    High Brass v Low Brass in Shotshells…Why?

    Shooting Tips
    Ron Spomer | October 28, 2015
    Every shotgunner knows that weak target and dove shotshells have low-brass heads. Really powerful magnum shotshells are built with high-brass bottoms to contain the incredible pressures generated by the huge loads of powder they contain. Except they don’t.
    All shotgun shells are standardized at maximum average breech pressures so that all shotshell and shotgun manufacturers can build their products for proper safety as well as performance. These ANSI (American National Standards Institute) pressure limits might surprise you. These are taken from the NRA Firearms Sourcebook published in 2006.

    Shell pounds per square inch (p.s.i.) ANSI Max. Av. Breech Pressure
    in pounds per square inch (p.s.i.)
    10 ga. 3.5″ 11,000
    12 ga. 3.5″ 14,000
    12 ga. 3″ 11,500
    12 ga. 2.75″ 11,500
    16 ga. 2.75″ 11,500
    20 ga. 3″ 12,000
    20 ga. 2.75″ 12,000
    28 ga. 2.75″ 12,500
    .410 bore 2.5″ 12,500
    .410 bore 3″ 13,500
    .300 Win. Mag. (for perspective) 64,000

    Who’d have imagined the puny .410, which is really a 67 gauge (67 balls of lead that fit bore diameter can be cast from a pound of lead,) would be rated for the highest pressures among shotgun shells?
    The truth is, shotshell pressures can be safely handled by all plastic hulls with no brass anywhere. So, if the brass heads on shotshells aren’t there to contain gas pressures, what’s going on? Why even have them?
    Part of the reason is function, part is history. Functionally, a brass head makes it easy to insert and hold metal primers, even through numerous reloadings, which target shooters appreciate. Winchester AA hulls are justly famous for their reloadability.
    Historically, back in the black powder era, when the first self-contained shells were invented, they had to be made of a substance that would hold up to rough handling while safely containing the primer, powder and shot. Plastics weren’t yet invented. That left paper or metal of some kind. Brass was cheap, malleable and already being used for rifle cartridges, so they used it to make shotshells. The all-brass shotshell was manufactured until shortly after 1900 when the paper hull was perfected. The brass base was retained to firmly grasp the primer and contain the hot, burning powder. The tightly wrapped and waxed paper around the shot was more than adequate for holding it. Upon firing, all it had to do was swell against the chamber walls, which then absorbed all the pressure of the powder gases. But a problem developed.
    Black powder was relatively weak, so a lot of it was needed to generate adequate velocities. To keep it from burning pinholes through paper hulls, brass was extended farther up the sidewalls. Shotgunners soon learned that high-brass shells meant they were loaded with more powder — the magnums of their day.
    Once high-energy, smokeless powder took over, shooters still assumed high-brass indicated more powerful shells, so manufacturers maintained the tradition even though the smaller quantities of smokeless powder rested well below the paper or plastic portion of the shell.
    Today’s plastics are fully capable of holding primers and containing powder, wads and shot through the life of the shell, including firing, but shotgunners are firmly wedded to the brass shotshell base. Not only that, they still associate power with an ever higher brass base, which is why today’s target and light game shells are still loaded in low-brass hulls and magnum shells are loaded in high-brass hulls. It isn’t necessary, but it does make it easier to determine relative power levels of shells at a glance.

  9. #9
    Boolit Master
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    And today no shotshell has a brass bottom!
    It's brass plated iron.

    How do you think shotshell catchers work


  10. #10
    Boolit Master
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    High pressure in shotshells will show at the primer pocket, too much pressure and primer pocket expands enough that re-priming will go in too easy and could fall out in your gun. This happens on semis when the shell goes from mag. to chamber. Trouble in the chambers is usually just a rough chamber from rust/neglect/etc.

  11. #11
    Boolit Master
    swheeler's Avatar
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    ........and it probably won't too many of those loads without breaking the extractor
    Hell, I was there!

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Abbreviations used in Reloading

BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
C Compressed Charge PR Primer SPCL Soft Point "Core-Lokt"
HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
PSP Pointed Soft Point Spz Spitzer Point SBT Spitzer Boat Tail
LRN Lead Round Nose LWC Lead Wad Cutter LSWC Lead Semi Wad Cutter
GC Gas Check