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pierced primers

Discussion in 'GATE AR-15 Forum' started by sk330lc, Apr 5, 2010.

  1. sk330lc


    Jan 25, 2009
    What is the cause of pierced primers?
    I have a RRA 16" Carbine with the 233 Wylde chamber. For some reason It will pierce about 3 to 5 rounds out of 50. the primers are Not Flat or really showing High pressure. It does it with Hornady, Remington, Winchester, and Fiochi. It does not do it with PMC Or PPU. that I have noticed.
    I changed out Fireing pins thinking maybe that was it.
    I have noticed it does it more with about 5 to 6 rounds down the tube. Could the chamber being hot raise the pressure enough to cause this?

    Thank you for any insite you could give. I would hate to have to send the upper back to RRA.
  2. Constructor

    Constructor Moderator

    Dec 10, 2009
    It is usually high pressure, if rounds are fired quickly cases may show higher pressure, I have noticed similar high pressure signs with M193 ammo.
    Too much oil in the bore can cause high pressure, after cleaning run a dry patch through the bore to remove excess oil. Copper fouling or carbon fouling can cause higher pressure.
    You may also check the length of the bolt, it should be 2.80, if the bolt is too short the firing pin may protrude too far from the bolt face and pierce the primers or make the primers easier to pierce.
    They even make firing pin protrusion gauges but not exactly sure where to find one maybe Brownells.
    The thing that bothers me is these are all factory loads and not m193 or is it?
    M193 is known to be a little warm but if these are factory loads something in the barrel or chamber is causing the high pressure. If the barrel is clean and still shows pressure like that I would send it back to RRA to have the bore checked unless you happen to have a .218 pin gauge handy.
    Last edited: Apr 6, 2010

  3. sk330lc


    Jan 25, 2009
    "I would send it back RRA " I was afraid you were going to say that.
    The ammo was not m193. It was just std. 223 loads from the manufactures I listed. The PPU and PMC might be using thicker primers?
    I'll give R.R. a call and send it back to be checked just to be safe. I don't have the proper tools to check the head space and the firing pin protrusion.
    Thanks for the help. !