Causes of light firing pin hits

Discussion in 'Handloading and Reloading' started by Eddy19, Jan 17, 2020.

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  1. Eddy19

    Eddy19 Member

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    Earlier this week at the range the guy next to me had a cartridge with just a slight dent in the primer which failed to ignite it. I've never had this happen. The idea of a not fully seated primer (reloading related) seems to make sense.

    UPDATE: it was a S&W 357 pistol, don't know which model.

    Your thoughts of other things that can cause this?...thanks.
     
    Last edited: Jan 17, 2020
  2. murf

    murf Member

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    dirty firing pin channel.

    murf
     
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  3. fguffey

    fguffey member

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    Pistol or rifle? I would suggest he clean his firearm and check firing pin spring.A light springs can cause holes in the primer.

    F. Guffey
     
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  4. WrongHanded
    • Contributing Member

    WrongHanded Contributing Member

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    Recently I had a Remington UMC .357 Sig cartridge fail to ignite after multiple strikes. Looked like the primer pocket may have been too deep on that one.
     
  5. drband

    drband Member

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    In some pistols that have a FP retaining roll pin, the roll pin can become deformed after a lot of dry fire causing the firing pin to hang up and not travel far enough (light strike) or worse, to hang in the extended position leading to possible slam fires on cycling.

    I had a P938 .22 conversion slide that had this problem. Replaced the roll pin to correct it. I believe CZ uses a FP retaining roll pin. There are aftermarket stronger roll pin replacements to eliminate the problem.
     
  6. edwardware

    edwardware Member

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    - I think he didn't have the bolt rotated all the way down into battery.
    - I think he wasn't depressing the grip safety all the way and the Swartz FP block was dragging.
    - I think the hammer nose rivet was probably loose so the FP wasn't fully contacting the primer.

    Now tell us what action type you're imagining, and I'll pick one. . .
     
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  7. ATLDave

    ATLDave Member

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    There's one thing that causes light primer strikes - insufficient power delivered to the primer cup relative to the hardness/toughness of the cup and the sensitivity of the priming compound.

    That has 4* main "flavors" of causes:
    • Insufficient spring motive power on the hammer or striker in the first place - not enough energy in the system from the get-go. Light hammer springs are an example. This is also common in S&W revolvers when the strain screw (which applies tension to the mainspring) is backed out (sometimes done on purpose in an attempt to lighten the trigger pull).
    • Something sapping striking power along the way to the strike. A dirty firing pin channel, a too-strong firing pin spring, a hammer dragging on the frame, a firing pin safety not getting totally clear... all these are ways to take power out of the strike before the strike happens.
    • Something happening during the strike to sap power from deformation of the cup. Insufficiently seated primers are the main example here (although really sloppy headspacing could do it, too).... because it diverts some of the strike's power into seating the primer.
    • The cup is just too hard and/or priming compound too insensitive for the way the gun is built or set up. This is really the flip side of the first one - at a certain point, particularly with revolvers and DA autos, there is a limit on how light the trigger can be gotten while still being able to set off all primers. There are people who intentionally and deliberately set up revolvers such that only federal primers (generally the softest and/or most sensitive) will reliably ignite. If you put some Tula or CCI primered-ammo in such a gun, you will get light strikes. You can fix this by increasing the energy available, which will add weight to the trigger's pull, or you can switch to softer primers.


    * It's really just 3, with the 4th I've listed being the same as the 1st, but assuming the initial energy of the system is non-negotiable.
     
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  8. ReloaderFred

    ReloaderFred Member

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    If they were reloads, he hadn't seated the primer all the way to the bottom of the primer pocket. The resultant moving of the primer when struck cushions the blow of the firing pin, leaving a lighter than normal indentation.

    Hope this helps.

    Fred
     
  9. straightshooterjake

    straightshooterjake Member

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