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Thread: why can some 1/9's shoot 75's and 80's and not others?

  1. #21
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    Quote Originally Posted by Ring View Post
    i have, sub MOA, around 2.5" about what i get with my 40gr vmax
    SUB MOA at 300yds?? Got pics as I am not quite believing it.


    C4

  2. #22
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    A-Max is a VLD design. Those have to have 1 in 8" or quicker to stabilize. They're also long enough that they can't be loaded to mag length.

    Hornady 75 BTH is a different bullet. Those too prefer quicker twists, but if you have a "quickish" 1 in 9", they can work. These can be laoded to mag length, as can the 75 Nosler BTHP, the 77 grain Sierra and the 73 grain Berger. But as soon as you get into any VLD design, they are designed for slowfire competition, and are single loaded to ensure bullet ahs minimal jump to lands. Often these OALs run around 2.450"

  3. #23
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    DMR brings up something that makes me think that this is an example of a document crafted around a specific seller's item and not from someone that knows what they are doing to acquire the best fitting item.

    "The U.S. Department of State, INL Section, U.S. Embassy Bogota, Colombia , has a requirement for the purchase of a six hundred (600) M4A1 type assault rifles, to be donated to the government of Colombia for INL program purposes."

    "Rifling: 1 turn in 9 (22.8 cm) R.H. twist, 6 grooves and lands (this is an absolute requirement, no other twist rate is acceptable), weight not to exceed 6.5 lbs, mode of operation semi auto and 3 shot burst. "

    Within the military an M4A1 is differentiated from an M4 by being equipped with a full-auto trigger group, whereas the M4s are equipped with the crappy A2 burst mechanism. M4A1s feature a 1:7 twist rifling, there have never been any M4A1s with 1:9 barrels. The twist rate printed on the barrel is irrelevant. If they had a need for the rifle to shoot a particular bullet/cartridge, that should have been part of the document, as in, "Must achieve under 6" groups at 300 yards with M193 from a machine rest". It's the performance that is supposed to matter, not the method. This implies to me that the author of the document does not know what an M4A1 really is, and is being fed twisted information by the vendor or a supporter of the vendor.

    There are some very angry dudes that can tell you what happens when you write a document with the intention of getting something that everybody thinks is great, and they don't show up to compete for the contract and you get something you really didn't want because the wrong language was used in the requirements.
    Last edited by Failure2Stop; 06-19-09 at 09:50.
    Jack Leuba
    Director, Military and Government Sales
    Knight's Armament Company
    jleuba@knightarmco.com

  4. #24
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    Quote Originally Posted by Failure2Stop View Post
    "Rifling: This implies to me that the author of the document does not know what an M4A1 really is, and is being fed twisted information by the vendor or a supporter of the vendor. "
    Damn I need to quit multitasking. M-4A1 and 3 shot burst together should have flagged the writer isn't realy well versed on what they are writing.
    Last edited by DMR; 06-19-09 at 10:14.
    pro-patria.us

  5. #25
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    Quote Originally Posted by rainman View Post
    Friend of mine and I bought identicle URs with 1:9 barrels a number of years ago.

    Both URs shot XM193 and Hornady TAP 75gr interchangeably, and grouped well.

    Being my only 1:9 AR, I consider mine to be my "beater"; meaning that if I'm going to be doing lots of drills/rapid fire at moderate distances, that's the gun I use. As such, I have many rounds through it, and it continues to shoot heavy bullets well.

    Friend's UR, a "backup" piece (only shot occasionally) with far fewer rounds, just started "patterning" (uses most of an IPSC target at 100 yards) one cold (mid-30's) day, and has never been able handle heavy bullets since then, under any conditions.

    My beater continues to rack up the rounds and shoot the 75gr well.

    Friend's lightly used/identicle UR started patterning with 75gr, and it was not a gradual thing...like someone threw a switch...one day it was "grouping", the next it was "spraying"....yet it still shoots XM193 with the same accuracy!



    Interesting...

    -Rainman
    I'm sure your friend has already checked it out, but any gun that changes its accuracy "like someone threw a switch", I would want to look for other reasons than rifling twist...
    never push a wrench...

  6. #26
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    I just caught this post. You are exactly correct. Whomever wrote this crap is a Mk 1 MOD0 asshole and doesn't know his dick from a dipstick. Oh wait, did I see that dreaded agency "Dept. of State" mentioned? That says it all.

    Quote Originally Posted by Failure2Stop View Post
    DMR brings up something that makes me think that this is an example of a document crafted around a specific seller's item and not from someone that knows what they are doing to acquire the best fitting item.

    "The U.S. Department of State, INL Section, U.S. Embassy Bogota, Colombia , has a requirement for the purchase of a six hundred (600) M4A1 type assault rifles, to be donated to the government of Colombia for INL program purposes."

    "Rifling: 1 turn in 9 (22.8 cm) R.H. twist, 6 grooves and lands (this is an absolute requirement, no other twist rate is acceptable), weight not to exceed 6.5 lbs, mode of operation semi auto and 3 shot burst. "

    Within the military an M4A1 is differentiated from an M4 by being equipped with a full-auto trigger group, whereas the M4s are equipped with the crappy A2 burst mechanism. M4A1s feature a 1:7 twist rifling, there have never been any M4A1s with 1:9 barrels. The twist rate printed on the barrel is irrelevant. If they had a need for the rifle to shoot a particular bullet/cartridge, that should have been part of the document, as in, "Must achieve under 6" groups at 300 yards with M193 from a machine rest". It's the performance that is supposed to matter, not the method. This implies to me that the author of the document does not know what an M4A1 really is, and is being fed twisted information by the vendor or a supporter of the vendor.

    There are some very angry dudes that can tell you what happens when you write a document with the intention of getting something that everybody thinks is great, and they don't show up to compete for the contract and you get something you really didn't want because the wrong language was used in the requirements.



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