Guns International

Just a thunkin', gas volume vs gas pressure

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  • TEXAS "All or nothing"

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    Mar 24, 2021
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    Any thoughts on what you may or may not know? On automatic(bar or similar) vs ar style(gas length vs gas port size) effects. With + 1, 2 and 3" rifle length that is sometimes a failure? Example: I have an AP 6.5cm 22" barrel w/standard length rifle gas system and it functions perfectly with factory ammo, but PR +2 with same ammo is a bust! Now I also have a CBI and Faxon standard rifle length system that pops primers with the same factory ammo. I haven't varified port size for any reference and haven't tried using a h2 or h3 buffer yet. The local gunsmith moved so I don't have anyone close to check or open port size up. Lots of food for thought.
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    Texasjack

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    Timing is likely an issue, rather than just pressure. When does a particular powder reach peak pressure when fired? That will be affected by the length of the barrel and on an gas-driven action, the distance to the port could be affected.
     

    Dawico

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    Powder pressure curve could be an issue. Some powders spike too early or late to work well in auto loaders. H4831 is notorious for this.

    With factory ammo it could be a few different issue though, including QC issues from the manufacturer, your chamber size and throat depth, how dirty your barrel is, and even the ambient temperature outside. Add in the fact that some rifles are just finicky and bad combos are common with them.

    Hornady factory rifle ammo has always ran hot for me. Severely flattened primers and damaged brass is very common amplified by the fact that I think their brass is junk.

    There's a reason everyone says try different ammo before sending a gun in for repair.
     

    TEXAS "All or nothing"

    Active Member
    Rating - 0%
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    Mar 24, 2021
    922
    76
    Texas
    Powder pressure curve could be an issue. Some powders spike too early or late to work well in auto loaders. H4831 is notorious for this.

    With factory ammo it could be a few different issue though, including QC issues from the manufacturer, your chamber size and throat depth, how dirty your barrel is, and even the ambient temperature outside. Add in the fact that some rifles are just finicky and bad combos are common with them.

    Hornady factory rifle ammo has always ran hot for me. Severely flattened primers and damaged brass is very common amplified by the fact that I think their brass is junk.

    There's a reason everyone says try different ammo before sending a gun in for repair.
    To hot for an AR.... well most of them, but fine in the AP barrel. Most aren't ar tested, just ba tested. I try and run factory ammo in new barrels, but with what I've experienced I'll just use new brass and use 2/3-3/4 loads for AR platforms. Piss on new(factory) ammo!
     
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