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Thread: Weird AR9 barrel with a 1:7 twist.

  1. #1
    Boolit Master klcarroll's Avatar
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    Weird AR9 barrel with a 1:7 twist.

    I recently purchased a lot of AR parts, and included were three new AR9 barrels, ...all stamped "Palmetto".

    The thing that puzzles me is that they feature a 1:7 twist! I have NEVER seen a twist that fast on a 9x19 barrel!

    I sent Palmetto State Armory an email asking about the barrels, but they have not responded.

    ......Has anyone here had any experience with a twist this fast in a 9x19 barrel?? I'm wondering if they would be usable with really "heavy for caliber" cast boolits.
    KLC


    “.....Nuttier than a squirrel turd.” - An assertion by a fellow forum member

  2. #2
    Boolit Master

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    Is that engraved on the barrel, and have you verified that twist with a cleaning rod.

    My guess is that when they engraved the barrel, they forgot to edit the 223/556 twist designation

  3. #3
    Boolit Master klcarroll's Avatar
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    Yep! .......I did physically check it: ....But I knew before I even did it that the marking was correct.

    I have several weapons in .300 AAC, so I have gotten rather used to looking at 1:7 twists.
    KLC


    “.....Nuttier than a squirrel turd.” - An assertion by a fellow forum member

  4. #4
    Boolit Buddy
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    Could they have been for the 9x39 originally? and chambered to 9x19 instead
    Last edited by shell70634; 09-01-2020 at 07:21 PM.
    "EXPERT= Ex is a has been, spurt is a drip under pressure" Unknown

  5. #5
    Boolit Grand Master

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    Possibly extra heavy sub sonic bullets with a supressor?

  6. #6
    Boolit Master

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    I can't envision a need for a 1 in 7 twist 9mm barrel. Even a 1 in 12 twist will stabilize a 300 grain 358 bullet. A 1 in 14 twist marginally stabilizes/stabilizes the 300/310 grain cast bullets.

  7. #7
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    tomme boy's Avatar
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    If you sent a regular email, good luck getting them to respond. Go over to AR15.com and go to the industry section and to PSA forum. Ask Jeremiah there. It is the fastest way to get a hold of PSA. He will be the person you need to talk to anyway. Their barrels are 1-10 not 1-7. It probably was roll marked wrong.

  8. #8
    Boolit Master
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    I have an AR9 from PSA that doesn't shoot well at all. thanks for the tip i will check it out.

  9. #9
    Boolit Master

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    I could see a 1 in 10 twist. I am not up on 9mm barrels, but I think I've seen the 1 in 10 9mm referenced elsewhere. 1 in 10 seems sorta common for larger caliber subsonic chamberings

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Abbreviations used in Reloading

BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
C Compressed Charge PR Primer SPCL Soft Point "Core-Lokt"
HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
PSP Pointed Soft Point Spz Spitzer Point SBT Spitzer Boat Tail
LRN Lead Round Nose LWC Lead Wad Cutter LSWC Lead Semi Wad Cutter
GC Gas Check