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Signs of underpressure on cartridges

Discussion in 'Reloading' started by chemcmndr, Apr 19, 2010.


  1. chemcmndr

    chemcmndr
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    I have been unable to find any information on this topic, so I look to more experienced people. I've seen a good bit of information on the signs of overpressure on cartridges, such as the flattening of the primer, etc. What about when a round doesn't have as much pressure as it should? I ask because I was shooting some reloaded 9mm and noticed that there was some soot on the outside of the brass near the case mouth, almost as if the case wasn't expanding fully in the chamber. The rounds were loaded with Hodgdon Universal to the minimum powder amount and did cycle the slide, but sometimes the slide wouldn't stay open on the last shot. These are the reasons that lead me to think that my rounds may be a little underpowered.

    Any suggestions, remarks, or comments?
     

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  2. tlafrance

    tlafrance
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    A chronograph is a good starting place. Actual velocity vs published velocity for that load will tell you quite a bit.

    Tom
     

  3. unclebob

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    All of those are signs that you do not have enough powder in the cartridge.
    Just because it is published minimum charge, that it well work in your gun X but it works in gun Y
     
  4. Colorado4Wheel

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    Universal is a little dirty when not pushed to mid level loads.
     
  5. fredj338

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    It's why I never recommend starting charges for semuiautos. They often barely work the action or fail to give 100% reliablility. The slower the poder, the more you'll see under pressure signs that you noted. You'll also find more unburned powder in the gun & around the shooting area. Universal & other med burners are at their best above midrange pressure/vel levels.
     
    #5 fredj338, Apr 19, 2010
    Last edited: Apr 19, 2010
  6. PCJim

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    As already stated, the two characteristics of those 9mm rounds indicate underpressure - black, sooty case mouths and failure of the slide lock after shooting the last round.

    The greatest sign of underpressure is a stuck bullet in your barrel.:whistling:
     
  7. GLShooter

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    Right on that assessment. Bump the charge a tad and have at it. The 9 MM is pretty forgiving on the pressure levels so a published MAX is usually pretty darn safe.

    Greg
     
  8. WiskyT

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    Getting hit in the face with powder particles is a good sign of too low pressure. 3.5 Bullseye with a 180LTC in 40SW worked well as a reduced load for me so I tried 3.0. In my Glock 27 it worked great, but I got "stuff" hitting me in the face with that load in my Beretta 96. So I went back to the 3.5 load to have a load for both guns. The 3.0 load shot well and cycled both guns well, but obviously it wasn't sealing the case in the Beretta.
     
  9. cysoto

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    +1

    I have had the same experience with Titegroup.
     
  10. Jayman

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    I'll find powder particles on my hands/arms too, if the charge is super light.
     
  11. WiskyT

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    Some powders leave lots of unburnt particles even with high charges. Shoot a box of full load 357Mags loaded with 296 and you'll find a pile of powder on the floor in front of you and powder all over your arms.
     
  12. robin303

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    Roger that. That is the problem I have had with Blue Dot. I'm glad I ran out of that stuff.
     
  13. Jeff82

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    Pushed out ("high") primers and/or soot around the primer pocket.
     
    #13 Jeff82, Apr 23, 2010
    Last edited: Apr 23, 2010
  14. njl

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    Who reloaded them?
    What brand/type/grain bullet?
    How much powder?
    COAL?

    I've been shooting 124gr FMJ/CMJ/JHP from PD and MG with minimal loads of Universal (4.3-4.4gr) and though I do sometimes get some sooty brass, I've shot several thousand through a variety of Glocks (everything from the 26 to the 34) and not a single malfunction.
     
  15. gwalchmai

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    Take a careful look at this pic. Notice the discoloration 1/8" above the rim. That is an indication that you may want to check your load.
     

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  16. DEADLYACCURATE

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    wtf happened here^^^
     
    #16 DEADLYACCURATE, Apr 24, 2010
    Last edited: Apr 24, 2010
  17. gwalchmai

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    Sent to me from a friend. I assume a double charge.
     
  18. njl

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    So...what's that got to do with signs of underpressure?
     
  19. argy1182

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    Thanks for the topic. A lot of my lighter loads have been gathering soot around the mouth. They cycle my g21sf just fine, but do not cycle most 1911s reliably. Time to bump it up a little.

    Learn something new everyday...much appreciated.
     
  20. gwalchmai

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    One of the classic signs of underpressure is the sooty discoloration caused by insufficient obturation. As my pic illustrates, many of these signs can be caused by other factors...
     
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