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Thread: 12.5" velocity loss?

  1. #11
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    14.5" and 10.3" data

    It's not for 12.5", or 75 grain loads, but you can see the trend. I talked to a gent at Federal/ATK recently, and he said the LE223T1 load in the table below was effective from a 10.5" for at least 125yd and up to 200yd, as far as initial upset and expansion goes. After that, it would basically behave like XM193. For my application (suburban LE), 125yds is plenty. For hunting however, depending on you're anticipated ranges and prey, these velocities/ranges may not be enough. My personal thought is that if you want an SBR, get 11.5" or less. Otherwise, a 14.5" with a perm'ed hider is only 2-3" longer overall than the 12.5", and you're saving the $200 tax stamp. Just my thoughts.

    Attachment 7402
    Chrono'ed on a F1 Shooting Chrony at 10' from the muzzle, by me. Speeds are in FPS.

    Obviously, I'm not as high speed as Molon . But as you can see, you're losing upwards of 350fps with the 4" reduction in barrel length.

    BTW, the chrono I used is around $100. Works well enough for me.
    Last edited by wilco423; 02-13-11 at 23:30.

  2. #12
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    Thanks for the info Wilco!

  3. #13
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    Great stuff wilco!

    I think the 12.5 is a good "in between" length (between super short 10" and 16"). You dont lose too much velocity, or lose any maneuverability.

    I'll probably go 12.5 just in case i want to add a suppressor later, cut down on OAL.

  4. #14
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    You're welcome, and I hear you on the 12.5" - certainly if you want it to be more effective at longer ranges, the added length helps.

    Also, I don't know if it will become available to the public, but the new FBI contract round from Federal is a 5.56 NATO loading, and should get M855 type velocities. In theory, that would extend the "effective" range a bit over the duty load we use (223 pressure 55 grain). According to the guy I spoke to, they're also developing a SBR specific cartridge, which ATK says might be released later this year.

  5. #15
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    I'm a big fan of the balance the 12.5 brings for hunting applications and the OAL as well.

    I'm reading where the 6.8 is really getting some impressive velocities out of SBR's...i think if I had to do it over again, this would have been my choice over 5.56.
    "You cannot invade the mainland United States. There would be a rifle behind each blade of grass."
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  6. #16
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    If you really need the terminal performance at 300 meters, then go with 6.8.

    If you go with 5.56, then I would choose the non fragmenting bullets such as the TSX or bonded SPs at that distance.

  7. #17
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    Ok i THOUGHT i had done my research here and understood the NFA process....then i went to my local class 3 dealer and my head is spinnning.

    What i thought:
    1. decide you want a sbr
    2. get your lower engraved
    3. fillout Form 1 completely (finger print, signature, ect)
    4. Mail in form with $200 check for tax stamp
    5. Wait for approval, once it passes...
    6. Buy upper, have it shipped to house (just like a normal upper), bam you have your sbr.

    What my dealer says...

    1. Order upper (sent to the gunshop)
    2. fillout Form 1 completely (finger print, signature, ect)
    4. Mail in form with $200 check for tax stamp
    5. Wait for approval, once it passes...
    6. get your lower engraved...now you have a sbr.
    Last edited by J-Dub; 02-16-11 at 11:44.

  8. #18
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    Both of those timelines will work.

  9. #19
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    If you want to build your own SBR, there is no reason to involve the gunshop in the process. What your dealer says doesnt even make sense. One, uppers are not the NFA item. Second, if you buy an SBR from a dealer, it is on a Form 4 (transferring an existing NFA item). Since you are not making it, there is no need to engrave anything.

    Quote Originally Posted by J-Dub View Post
    Ok i THOUGHT i had done my research here and understood the NFA process....then i went to my local class 3 dealer and my head is spinnning.

    What i thought:
    1. decide you want a sbr
    2. get your lower engraved
    3. fillout Form 1 completely (finger print, signature, ect)
    4. Mail in form with $200 check for tax stamp
    5. Wait for approval, once it passes...
    6. Buy upper, have it shipped to house (just like a normal upper), bam you have your sbr.

    What my dealer says...

    1. Order upper (sent to the gunshop)
    2. fillout Form 1 completely (finger print, signature, ect)
    4. Mail in form with $200 check for tax stamp
    5. Wait for approval, once it passes...
    6. get your lower engraved...now you have a sbr.

  10. #20
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    Thats what i thought...thanks.

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