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Thread: 5.56 NATO Ammo Question.......?????????????????????????????

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    Default 5.56 NATO Ammo Question.......?????????????????????????????

    This question is reference the 62 gr. Armor Piercing cartridge. At what barrel length would 95% to 100% of the powder be fully burned.

    I have a lot of this ammo manufactured by FEDERAL.

    My secondary question is about muzzle flash.......Is there a barrel length at which point there would be zero flash (Forgetting the utility of a 30 foot long barrel). Yes, I understand about drag slowing the bullet beyond the point of maximum velocity while still in the barrel.

    Thank you,

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    Tough questions to answer really, without empirical data. But I have a question, if flash is the issue, are you trying to avoid a flash suppressor/hider? There are some really impressive flash hiders that will suppress a flash to nearly nothing even on 10" or so barrels.

    Not sure about burn rates and barrel lengths myself.

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    The military found that an 18 inch barrel was optimum for .223 55grn , 24 inch barrels for 7.62X51 and 26 -1/2 inch barrels for 30-06. That was a report from 1969 all right, maybe 62 grn SS109's are a bit different, or even the powder......
    If you can't Kill it with a 30-06, you should Hide.

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    The optimum length for M855/ss109 mil spec ammo is 20"

    Less than that, the velocity decreases, longer than that, velocity decreases.


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    Thank You Very Much..........I tried to give you some green reputation thingie, sadly I have to rep others first. My 24" barrel might be meeting Mr. Hacksaw soon.


    Quote Originally Posted by Akheloce View Post
    The optimum length for M855/ss109 mil spec ammo is 20"

    Less than that, the velocity decreases, longer than that, velocity decreases.


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    ImageUploadedByTapatalk1384570868.563076.jpg

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    I would get out the chrono before I grabbed the hacksaw. My 24" 223 shoots the early 55gr military stuff pretty close to 3300fps. How much faster is it supposed to get if I chop 4" of barrel? I'm not sure how fast it shoots the 62gr stuff as my 1/12 twist doesn't like it much.

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    Ordered in January, this was finally mailed to me today. I have high expectations from this 1 in 8 fluted 18" stainless steel upper with 62 gr. FMJ
    http://www.rockriverarms.com/index.c...ategory_id=569

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    Quote Originally Posted by Akheloce View Post
    The optimum length for M855/ss109 mil spec ammo is 20"

    Less than that, the velocity decreases, longer than that, velocity decreases.


    ImageUploadedByTapatalk1384570849.789240.jpg

    ImageUploadedByTapatalk1384570868.563076.jpg
    I'm not terribly smart, but I'm suspecting that the findings were that the acceleration percentage decreased after a certan barrel length, not that the actual velocity decreased. In a .223 Remington, all else being equal, increased barrel length will produce higher velocity at anything approaching common barrel lengths.
    Foolishness is a moral category, not an intellectual one.

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    oh ya! 20" A2 or die!
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    Quote Originally Posted by 1Cor15:19 View Post
    I'm not terribly smart, but I'm suspecting that the findings were that the acceleration percentage decreased after a certan barrel length, not that the actual velocity decreased. In a .223 Remington, all else being equal, increased barrel length will produce higher velocity at anything approaching common barrel lengths.
    Yeah, I'm thinking you're smart enough to know that shortening a 24" 223 barrel isn't going to increase velocity.

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    Member Akheloce's Avatar
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    Quote Originally Posted by 1Cor15:19 View Post
    I'm not terribly smart, but I'm suspecting that the findings were that the acceleration percentage decreased after a certan barrel length, not that the actual velocity decreased. In a .223 Remington, all else being equal, increased barrel length will produce higher velocity at anything approaching common barrel lengths.
    In just going off numbers from a suppressor manufacturers site. They claim all numbers came from real chrono numbers.

    I personally, if wanting minimum muzzle flash, would use a 24" with a flash suppressor..

    Then again, I I we're Really worried about muzzle flash, I'd use a milk jug, but that's just me.
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    Quote Originally Posted by AGL4now View Post
    This question is reference the 62 gr. Armor Piercing cartridge. At what barrel length would 95% to 100% of the powder be fully burned.

    ......................................

    Thank you,
    About 6" or so all the powder will be burnt (turned into a gas), the pressure from the expanding gasses will accelerate the bullet until etc. etc. .................................

    Just being a smart aZZZ.......
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    The flash is a non-issue for me.

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    Quote Originally Posted by Akheloce View Post
    In just going off numbers from a suppressor manufacturers site. They claim all numbers came from real chrono numbers.
    If that's the case then I'm calling them out, cause their assertion is indisputably false.............
    Foolishness is a moral category, not an intellectual one.

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    Quote Originally Posted by AGL4now View Post
    The flash is a non-issue for me.

    i like getting flashed by hot mommas.
    Semper Fi!

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    The 62 grain was designed for the mil and to the best of my knowledge it was targeted for the 16 to 20'' barrel 1/7 twist, secondly if it is the green tip it is not an armor piercing cartridge. Here is a short blurb on the history of the cartridge; ( Of the cartridges tendered, the 5.5645mm NATO was successful, but not the 55 gr M193 round used by the U.S. at that time. The wounds produced by the M193 round were so devastating that many[13] consider it to be inhumane.[14][15] Instead, the Belgian 62 gr SS109 round was chosen for standardization. The SS109 used a heavier bullet with a steel core and had a lower muzzle velocity for better long-range performance, specifically to meet a requirement that the bullet be able to penetrate through one side of a steel helmet at 600 meters. This requirement made the SS109 (M855) round less capable of fragmentation than the M193 and was considered more humane.[16]



    Performance
    The 5.5645mm NATO cartridge with the standard 62 gr. steel core bullets (NATO: SS109; U.S.: M855) will penetrate approximately 15 to 20 in (38 to 51 cm) into soft tissue in ideal circumstances. As with all
    spitzer shaped projectiles it is prone to yaw in soft tissue. However, at impact velocities above roughly 2,500 ft/s (760 m/s), it may yaw and then fragment at the cannelure (the crimping groove around the cylinder of the bullet).[20] These fragments can disperse through flesh and bone, inflicting additional internal injuries.[21]


    Fragmentation, if or when it occurs, imparts much greater damage to human tissue than bullet dimensions and velocities would suggest. This fragmentation effect is highly dependent on velocity, and therefore barrel length: short-barreled carbines generate less muzzle velocity and therefore lose wounding effectiveness at much shorter ranges than longer-barreled rifles. Proponents of the hydrostatic shock theory contend that the rapid transfer of energy also results in wounding effects beyond the tissue directly crushed and torn by the bullet and fragments.[5][6] These remote wounding effects are known as hydrostatic shock.[7]

    NATO Ball (U.S.: M855) can penetrate up to 3 mm (about 1⁄8 in) of steel at 600 meters.[22] According to Nammo, a Norwegian ammunition producer, the M995 can penetrate up to 12 mm (nearly 1⁄2 in) of RHA steel at 100 meters.[23]

    The US Army's Ballistic Research Laboratory measured a ballistic coefficient (G7 BC) of 0.151 and form factor (G7 i) of 1.172 for the SS109/M855 ball projectile.[24]

    The Swedish military has measured the bullet velocities of SS109/M855 military cartridges at 4 m (13.1 ft) from the muzzle fired from differing barrel lengths:[25]

    Barrel length SS109/M855 V4 bullet velocity
    210 mm (8.3 in) 723 m/s (2,372 ft/s)
    240 mm (9.4 in) 764 m/s (2,507 ft/s)
    270 mm (10.6 in) 796 m/s (2,612 ft/s)
    300 mm (11.8 in) 825 m/s (2,707 ft/s)
    330 mm (13.0 in) 843 m/s (2,766 ft/s)
    360 mm (14.2 in) 866 m/s (2,841 ft/s)
    390 mm (15.4 in) 878 m/s (2,881 ft/s)
    420 mm (16.5 in) 892 m/s (2,927 ft/s)
    450 mm (17.7 in) 906 m/s (2,972 ft/s)
    480 mm (18.9 in) 915 m/s (3,002 ft/s)
    508 mm (20.0 in) 922 m/s (3,025 ft/s)



    Criticism

    There has been much criticism of the allegedly poor performance of the bullet on target, especially the first-shot kill rate when the muzzle velocity of the firearms used and the downrange bullet deceleration do not achieve the minimally required terminal velocity at the target to cause fragmentation. This wounding problem has been cited in incidents beginning in the Vietnam War, first Gulf War, Somalia, and in the conflicts in Iraq and Afghanistan. In lab testing of M855, it has been shown that the bullets do not fragment reliably or consistently from round-to-round, displaying widely variable performance. In several cases, yawing did not begin until 710 in of penetration. This was with all rounds coming from the same manufacturer.[26] This lack of wounding capacity typically becomes an increasingly significant issue as range increases (e.g., ranges over 50 m when using an M4 or 200 m when using an M16) or when penetrating heavy clothing, but this problem is compounded in shorter-barreled weapons. The 14.5 inches (37 cm) barrel of the U.S. military's M4 carbine generates considerably less initial velocity than the longer 20" barrel found on the M16, and terminal performance can be a particular problem with the M4.

    Sorry this turned into a bit longer that I expected but I will add that I shoot both 55gr and 62gr in both a 16'' and 20'' AR platform and they both are consistent to 1/2 to 3/8 moa groups all day long.
    Hope this helps some.

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  17. #17

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    WOW......Great Information, Thank You.

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