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Thread: Newbie SBR/Ammunition Question

  1. #11
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    Quote Originally Posted by markm View Post
    Shooters on this site know that accuracy isn't a function of barrel length.

    What good is accuracy if the bullet is traveling too slow to accomplish anything? At that barrel length, a 9mm SBR would be better.
    How much velocity is lost when firing .556 from 7.5" barrel opposed to a 14.5" or 16" carbine? I know this will differ with ammo brand and quality. Just looking for some kind of average comparison.

  2. #12
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    I might be wrong, but wasn't the SBR designed for close combat ? Velocity lost in a 7.5" barrel within 25 yards will do the job just fine and rip off Ali Mujahadin's head, no doubt... Personally I would love a Diplomat because it's pure sex

    Last edited by SonicKrack; 05-19-09 at 16:05.
    Noveske Light Recce/AAC M4-2000 mod 08
    Noveske 7.5" VLTOR VIS Diplomat
    LWRC 10.5" gas piston upper with Blackout FH
    Walther P22/Tac Quest
    H&K Tactical Compact .45/AAC Evolution 45
    H&K P2000 .40 Duty
    KEL-TEC SU22 Semi Auto .22 rifle/threaded


    Next project: Some sort of machine gun...

  3. #13
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    Isn't it like 30-40fps per inch? (think I remember that in the deep recesses of my brain)

    7.5" vs. 14.5" = -7" * 40fps = 280fps loss


    I'm not sure I'd consider that too much velocity loss (if it's correct) being that the rifle would be mainly used for up close and personal stuff anyways, right?
    Time flies when you throw your watch.

  4. #14
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    Zhurdan,

    You gave the perfect answer...
    Noveske Light Recce/AAC M4-2000 mod 08
    Noveske 7.5" VLTOR VIS Diplomat
    LWRC 10.5" gas piston upper with Blackout FH
    Walther P22/Tac Quest
    H&K Tactical Compact .45/AAC Evolution 45
    H&K P2000 .40 Duty
    KEL-TEC SU22 Semi Auto .22 rifle/threaded


    Next project: Some sort of machine gun...

  5. #15
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    Some interesting reading on SBRs and velocity and accuracy:

    http://www.bren-ten.com/agtman/id9.html
    Last edited by SonicKrack; 05-19-09 at 16:17.
    Noveske Light Recce/AAC M4-2000 mod 08
    Noveske 7.5" VLTOR VIS Diplomat
    LWRC 10.5" gas piston upper with Blackout FH
    Walther P22/Tac Quest
    H&K Tactical Compact .45/AAC Evolution 45
    H&K P2000 .40 Duty
    KEL-TEC SU22 Semi Auto .22 rifle/threaded


    Next project: Some sort of machine gun...

  6. #16
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    Ballistics tests conducted in standardized, calibrated ballistic gelatin, as they appeared in the Feb. issue of Guns Magazine:
    (Note: The measurements next to the rifle type is the weapon's barrel length)

    Federal 50gr. "TNT" Hollow Point
    Rifle/Velocity/Penetration
    AR15 16"/2958fps./7.5"
    HK53 8.3"/2363fps./9.5"

    Win 50gr. Ballistic Tips
    Rifle/Velocity/Penetration
    AR15 16"/3184fps./12.25"
    HK53 8.3"/2603fps./15"

    Federal 55gr. Hollow Point
    Rifle/Velocity/Penetration
    AR15 16"/2958fps./11.5"
    AR15 14.5"/2972fps./12.5"
    M4 11.5"/2802fps./11.5"
    M4 10"/2599fps./11"
    HK53 8.3"/2365fps./13.5"

    Federal 55gr. Tactical Bonded
    Rifle/Velocity/Penetration
    AR15 16"/2793fps./13.5"
    HK53 8.3"/2273fps./16"

    So as you can see, velocity and barrel length don't have negative effects on penetration. This holds true with handgun ammo as well. In tests, light, fast rounds tend to expand or fragment at high speeds. The slower rounds tend to penetrate and offer controlled expansion.
    Noveske Light Recce/AAC M4-2000 mod 08
    Noveske 7.5" VLTOR VIS Diplomat
    LWRC 10.5" gas piston upper with Blackout FH
    Walther P22/Tac Quest
    H&K Tactical Compact .45/AAC Evolution 45
    H&K P2000 .40 Duty
    KEL-TEC SU22 Semi Auto .22 rifle/threaded


    Next project: Some sort of machine gun...

  7. #17
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    Only after proper foundational and ongoing repetitive refresher training, cultivating warrior mind-set, and ensuring weapon system reliability do you need to worry about ammunition selection.
    Now that reality is out of the way....

    The issue with the 7.5 is that it is very likely that the bullet will never get going fast enough to reliably fragment/mushroom/whatever in soft tissue. Meaning, it's effectively putting nothing more than a .22" diameter hole in the target.

    This is why Mark says a 9mm in that length would be better. Even if it didn't mushroom/fragment/whatever it would still at least be putting a .33" hole in the target.

  8. #18
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    Quote Originally Posted by Zhurdan View Post
    Isn't it like 30-40fps per inch? (think I remember that in the deep recesses of my brain)

    7.5" vs. 14.5" = -7" * 40fps = 280fps loss


    I'm not sure I'd consider that too much velocity loss (if it's correct) being that the rifle would be mainly used for up close and personal stuff anyways, right?
    The rule of thumb is 50 fps per inch of barrel loss, 7 inches = 350 fps... quite insignificant in a home defense situation.
    Noveske Light Recce/AAC M4-2000 mod 08
    Noveske 7.5" VLTOR VIS Diplomat
    LWRC 10.5" gas piston upper with Blackout FH
    Walther P22/Tac Quest
    H&K Tactical Compact .45/AAC Evolution 45
    H&K P2000 .40 Duty
    KEL-TEC SU22 Semi Auto .22 rifle/threaded


    Next project: Some sort of machine gun...

  9. #19
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    Hey Rob,

    You are the guru when it comes to Noveske stuff. I got my first N4 Recce based on your research. You wouldn't have any sources that carry the Diplomat or Shorty, would you? I would really appreciate the reference.
    Noveske Light Recce/AAC M4-2000 mod 08
    Noveske 7.5" VLTOR VIS Diplomat
    LWRC 10.5" gas piston upper with Blackout FH
    Walther P22/Tac Quest
    H&K Tactical Compact .45/AAC Evolution 45
    H&K P2000 .40 Duty
    KEL-TEC SU22 Semi Auto .22 rifle/threaded


    Next project: Some sort of machine gun...

  10. #20
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    Quote Originally Posted by SonicKrack View Post
    The rule of thumb is 50 fps per inch of barrel loss, 7 inches = 350 fps... quite insignificant in a home defense situation.
    Yeah, I knew it was something like that. Maybe 30-40fps is for pistols (larger bore diameter). I've been primarily a pistol guy for years, so rifles are new (5-6 years) to me for the most part.

    I think there might be something to this whole "fragmentation" deal though. As rob_s pointed out, poking holes is good, but poking big nasty gooey holes in the BG would be better.

    rob_s,

    do you think even with a HP there wouldn't be enough velocity around the 2500-2700fps range? (I was considering a 10.5" Noveske, if and when they are in stock again). Honestly though, if it came to really needing a rifle for a bad situation, I'd probably grab the FAL anyways, an SBR'd 5.56 would most likely be a novelty.
    Time flies when you throw your watch.

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