Max Pressure

Discussion in 'Sako Long/Magnum Actions' started by Edwin Pugh, May 13, 2019 at 9:50 PM.

  1. Edwin Pugh

    Edwin Pugh Member

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    What would be safe max pressure in an 6.5x55 A-V carbine action? I usually don't push pressure but seeing very promising results with 140 grain SGK and 47 grains Reloader 22. Quickload has it at 53k for pressure. No signs on primer.

     

  2. paulsonconstruction

    paulsonconstruction Sako-addicted

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    The internet is not the place to ask this question, nor is this the best forum to ask it. That information is available from SAAMI & from the powder & bullet manufacturers & is based on testing data. If you want to risk injury trusting "Quickload", your braver than I am. If you want to accept someone's opinion, that is unknown to you, about what pressure is safe in YOUR rifle, then you are acting irrationally. The push for MAXIMUM velocity & pressure is a fool's errand. Find a load with a heavy for caliber bullet at moderate velocity that shoots accurately & you will have much better success when hunting game. Primer signs can be VERY misleading.
     
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  3. stonecreek

    stonecreek SCC Secretary Forum Owner SCC Board Member

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    The Sako action will contain several times the pressure at which the brass case fails, so it is not the action but the case which is the limiting factor. Even the old Model 94 Swedish Mausers (which many errantly believe to be weaker than other Mausers) will hold together under pressures which destroy the brass. Be advised, however, that just because the action doesn't "blow up" that it is not dangerous. No action will completely contain the high-pressure escaping gas and brass particles when a cartridge case fails, so you are at physical risk from loads which your gun may take in stride but your eyeball may not.
     
  4. kirkbridgershooters

    kirkbridgershooters Well-Known Member

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    Primers are not the indicator of pressure signs. You need to use a chronograph to help determine what your pressures are in regards to velocity and what pressure it takes to get that velocity...
     
  5. stonecreek

    stonecreek SCC Secretary Forum Owner SCC Board Member

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    Primers are not the best indicator of pressure, but there are certain features of fired primers which a handloader should pay attention to (in conjunction with other indicators).

    For instance, a pierced primer is typically a result of excessive pressures. Sometimes it is a result of using a primer with a weak or thin cup, but by definition, if a primer pierces then the pressures are too high for that component. The same is true of a cratered primer, provided the cause is not an overly large firing pin hole.

    Flattened primers can happen from not just high pressure, but from somewhat "loose" headspace. It is only if the case headspaces with minimal clearance (typically using a neck-sized only case previously fired in the same chamber) that primer flattening can be a pressure indicator. With neck-sized brass, the flatness of the primer (if of the same brand and lot) can be an indication of relative pressure comparing one load to another, but is certainly not an indicator of absolute pressure.

    In other words, if a fired primer (using a neck-sized case) is flat to the point of expanding into the bevel of the primer pocket, bolt lift exhibits extra resistance, and there is measurable case expansion, then the load is generating unsustainable pressures and might be approaching pressures that would cause a case to fail.

    I will agree with Kirk that a chronograph, although it doesn't measure pressure, is a useful tool for keeping within tolerable pressures. When velocity readings are measuring higher than anticipated then pressures are likely also higher than desired.
     

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