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5.56 ammo chioce mk318

Discussion in 'GATE AR-15 Forum' started by nickod, Feb 12, 2011.

  1. nickod

    nickod sammyb

    397
    0
    Oct 7, 2010
    so i recently built a great ar15 and am having a difficult time selecting a decent 5.56 ammo to stock up on for shtf stash. 5.56 tap is out due to avalibility and cost. i dont want a 223 load because the 5.56/223 round is so dependent on speed for terminal proformance. so basically what im looking at is mk262 -(clone,not real thing but pretty damn close) and mk318 ( real mcoy). both i can get for 75 cents a round or a little less. just cheap enough to run a few hundred through my ar n stash 500 for what ever. i want something more substantial than m193 and m855 so please if any one could give me opinions on mk262 and mk318 sost i would be forever grateful. 16" barel 1/7 twist.
     
  2. Constructor

    Constructor Moderator

    552
    5
    Dec 10, 2009
    Roaming
    Rumors say the 318 is NOT accurate, I would go with the 77s if it was me.
    And 55gr over the 62gr if that was the other choice.
     

  3. Molon

    Molon

    111
    20
    Aug 22, 2009
    Range Report: Black Hills MK262 Mod 1


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    The 77 grain MK262 ammunition produced by Black Hills Ammunition has been referred to as the most accurate mass-produced 5.56mm ammunition that has ever been type-classified and issued by the US Army. Since its inception, genuine MK262 has been manufactured solely by Black Hills Ammunition. For years, MK262 was only available to the civilian population as “seconds,” but more recently Black Hills has made first-run production lots available on the commercial market. It is the first-run version of MK262 Mod 1 that I tested for this report.

    MK262 Mod 1 is loaded in WCC 5.56mm brass and uses a cannelured version of the 77 grain Sierra MatchKing. The round is charged with a proprietary ball powder.



    The 77 grain MK262 Mod 1 projectile compared to the M193 projectile.

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    MK262 powder. (The squares of the red grid measure 1/10 of an inch.)

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    The specification for accuracy testing of MK262 calls for multiple 10-shot groups to be fired; which is exactly what I like to do for a range report. An accuracy (technically, precision) evaluation of the first-run MK262 Mod 1 ammunition was performed following my usual protocol. This accuracy evaluation used statistically significant shot-group sizes and every single shot in a fired group was included in the measurements. There was absolutely no use of any Group Reduction Techniques (e.g. fliers, target movement, Butterfly Shots).

    The shooting set-up will be described in detail below. As many of the significant variables as was practicable were controlled for. Also, a control group was fired from the test-rifle used in the evaluation using match-grade, hand-loaded ammunition; in order to demonstrate the capability of the barrel. Pictures of shot-groups are posted for documentation.

    All shooting was conducted from a concrete bench-rest from a distance of 100 yards (confirmed with a laser rangefinder.) The barrel used in the evaluation was free-floated. The free-float handguards of the rifle rested in a Sinclair Windage Benchrest, while the stock of the rifle rested in a Protektor bunny-ear rear bag. Sighting was accomplished via a Leupold VARI-X III set at 25X magnification and adjusted to be parallax-free at 100 yards. A mirage shade was attached to the objective-bell of the scope. Wind conditions on the shooting range were continuously monitored using a Wind Probe. The set-up was very similar to that pictured below.



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    The Wind Probe.

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    The test vehicle for this evaluation was one of my semi-automatic precision AR-15s with a 20” stainless-steel Lothar Walther barrel. The barrel has a 223 Wylde chamber with a 1:8” twist.

    Prior to firing the MK262 ammunition, I fired a 10-shot control group using match-grade hand-loads topped with the Sierra 77 grain MatchKing. That group had an extreme spread of 0.69”.



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    Next, three 10-shot groups of the MK262 Mod 1 were fired in a row with the resulting extreme spreads (from smallest to largest):

    0.96”
    1.12”
    1.21”

    for a 10-shot group average extreme spread of 1.10”. The three 10-shot groups were over-layed on each other using RSI Shooting Lab to form a 30-shot composite group. The mean radius for the 30-shot composite group was 0.33”. For those of you who might not be familiar with the mean radius, I’ve posted some information about it below.




    The smallest 10-shot group.

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    The 30-shot composite group.

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    I chronographed the Black Hills 5.56mm MK262 Mod 1 ammunition from a semi-automatic AR-15 with a chrome-lined, NATO chambered 20” Colt M16A2 barrel.




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    Chronographing was conducted using an Oehler 35-P chronograph with “proof screen” technology. The Oehler 35P chronograph is actually two chronographs in one package that takes two separate chronograph readings for each shot and then has its onboard computer analyze the data to determine if there is any statistically significant difference between the two readings. If there is, the chronograph “flags” the shot to let you know that the data is invalid. There was no invalid data flagged during this testing.

    The velocity stated below is the muzzle velocity as calculated from the instrumental velocity using Oehler’s Ballistic Explorer software program. The string of fire consisted of 10 rounds over the chronograph.




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    Each round was single-loaded and cycled into the chamber from a magazine fitted with a single-load follower. The bolt locked-back after each shot allowing the chamber to cool in between each shot. This technique was used to mitigate the possible influence of “chamber-soak” on velocity data. Each new shot was fired in a consistent manner after hitting the bolt release. Atmospheric conditions were monitored and recorded using a Kestrel 4000 Pocket Weather Tracker.




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    Atmospheric conditions

    Temperature: 79 degrees F
    Humidity: 37%
    Barometric pressure: 30.12 inches of Hg
    Elevation: 950 feet above sea level


    The muzzle velocity for the 10-shot string of the Black Hills 5.56mm MK262 Mod 1 ammunition fired from the 20” Colt barrel was 2848 FPS with a standard deviation of 10 FPS and a coefficient of variation of 0.35%!

    For those of you who might not be familiar with the coefficient of variation (CV), it is the standard deviation, divided by the mean (average) muzzle velocity and then multiplied by 100 and expressed as a percentage. It allows for the comparison of the uniformity of velocity between loads in different velocity spectrums; e.g. 77 grain loads running around 2,650 fps compared to 55 grain loads running around 3,250 fps.

    For comparison (and to give you an idea of how good the CV is for this factory loaded MK262 Mod 1 ammunition) the mil-spec for M193 allows for a coefficient of variation of approximately 1.2%, while one of my best 77 grain OTM hand-loads, with a muzzle velocity of 2639 PFS and a standard deviation of 4 FPS, has a coefficient of variation of 0.15%.




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    ….
     
    Auxiliaryjohn likes this.
  4. Molon

    Molon

    111
    20
    Aug 22, 2009
    Federal T556TNB1 (MK318 Mod 0)


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    A version of MK318 Mod 0 that is now available to the general public is being sold as Federal "white box" T556TNB1.The SOST projectile loaded in the MK318 Mod 0 cartridge has a nominal weight of 62 grains and a nominal length of 0.87”. It is constructed with a copper base and a small, non-bonded lead core in the ogive section of the bullet. Due to this higher copper to lead ratio, the MK318 Mod 0 projectile is longer than a traditional copper jacketed/lead core projectile of the same weight, but is still slightly shorter than an M855 projectile.


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    While it is often stated that the SOST projectile used in MK318 Mod 0 is similar to the Federal Trophy Bonded Bear Claw, the form of the SOST projectile more closely resembles that of Federal’s Trophy Bonded Tip projectile (without the tip of course.) As previously mentioned, the MK318 projectile does not have a bonded core.


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    The loaded MK318 Mod 0 cartridge has a nominal OAL of 2.20". The projectile does not have a cannelure per se, but the case mouth is crimped into the top relief band. The cartridge is sealed at the case mouth, however not with the asphalt sealant typically found on military ammunition. The primers are sealed and crimped. The casehead is stamped "FC 10". The cartridge is charged with ball powder.


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    A typical copper jacketed/lead core FMJ bullet will have a specific gravity of approximately 10.2. Due to its higher copper to lead ratio construction, the MK318 Mod 0 projectile has a lower specific gravity. When fired from typical AR-15 barrel lengths with a 1:9” twist rate, MK318 Mod 0 will have a gyroscopic stability factor of approximately 1.3.



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    When fired from typical length barrels with a 1:7" twist rate, MK318 Mod O will have a gyroscopic stability factor of approximately 2.2.



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    MK318 Mod 0 Chronograph Data

    Chronographing of the Mk318 Mod 0 ammunition was conducted using an Oehler 35-P chronograph with “proof screen” technology. All velocities listed below are muzzle velocities as calculated from the instrumental velocities using Oehler’s Ballistic Explorer software program. All strings of fire consisted of 10 rounds each.



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    Each round was single-loaded and cycled into the chamber from a magazine fitted with a single-load follower. The bolt locked-back after each shot allowing the chamber to cool in between each shot. This technique was used to mitigate the possible influence of “chamber-soak” on velocity data. Each new shot was fired in a consistent manner after hitting the bolt release. Atmospheric conditions were monitored and recorded using a Kestrel 4000 Pocket Weather Tracker.



    [​IMG]


    Atmospheric conditions:

    Temperature: 75 degrees F.
    Humidity: 47%.
    Barometric pressure: 29.97 inches of Hg
    Elevation: 950 feet above sea level




    Two different barrel lengths were used in obtaining velocity data; a 14.5” Colt M4A1 barrel and a 20” Colt M16A2 barrel. Both barrels have NATO chambers, are chrome lined and have 1:7” twist rates. Both barrels have low round-counts on them.


    M4A1 barrel.
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    M16A2 barrel.
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    For comparison, the MK318 Mod 0 ammunition was fired in sequence with two different brands of 62 grain M855 ammunition. The firing order for both barrels was as follows:

    1. A 10-shot string of Winchester Ranger M855
    2. A 10-shot string of MK318 Mod 0
    3. A 10-shot string of IMI M855

    Finally, the data:



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    The Crane Warfare Centers' publication, “U.S. Navy Small Arms Ammunition Advancements” reported that MK318 was “optimized” for the MK 16 with a 14 inch barrel and claimed it has a velocity of 2925 fps at 15 feet from the muzzle (presumably from said 14 inch barrel.) The lot of Federal T556TNB1 (MK318 Mod 0) that I chronographed from the Colt 14.5” M4A1 barrel would have a velocity of approximately 2889 fps at 15 feet from the muzzle (at standard atmospheric conditions.)
     
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  5. Molon

    Molon

    111
    20
    Aug 22, 2009
    Accuracy Evaluation of MK318 Mod 0

    An accuracy (technically, precision) evaluation of the MK318 Mod 0 ammunition was performed following my usual protocol. This accuracy evaluation used statistically significant shot-group sizes and every single shot in a fired group was included in the measurements. There was absolutely no use of any Group Reduction Techniques (e.g. fliers, target movement, Butterfly Shots).

    The shooting set-up will be described in detail below. As many of the significant variables as was practicable were controlled for. Also, a "control group" was fired from each barrel used in the evaluation using match-grade, hand-loaded ammunition; in order to demonstrate the capability of the barrel. Pictures of shot-groups are posted for documentation.

    All shooting was conducted from a concrete bench-rest from a distance of 100 yards (confirmed with a laser rangefinder.) The barrels used in the evaluation were free-floated. The free-float handguards of the rifles rested in a Sinclair Windage Benchrest, while the stock of the rifles rested in a Protektor bunny-ear rear bag. Sighting was accomplished via a Leupold VARI-X III set at 25X magnification and adjusted to be parallax-free at 100 yards. A mirage shade was attached to the objective-bell of the scope. Wind conditions on the shooting range were continuously monitored using a Wind Probe. The set-up was very similar to that pictured below.

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    The Wind Probe.

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    In order to establish a working baseline for the intrinsic accuracy of the 62 grain SOST projectile itself, when fired from a semi-automatic AR-15, I worked-up a SAAMI pressure hand-load with pulled MK318 bullets and fired a 10-shot group of that load from a Krieger barreled AR-15 from a distance of 100 yards. The Krieger barrel has a 1:7.7” twist rate.

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    Prior to firing the 62 grain SOST hand-load, I fired a 10-shot control group consisting of hand-loaded 62 grain Berger hollow points. The extreme spread for the control group measured 0.66”.


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    The extreme spread of the 10-shot group of the 62 grain SOST hand-load measured 1.9”.


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    Since MK318 Mod 0 is intended for use as a combat round, I used AR-15s with chrome-lined, NATO chambered barrels for this accuracy evaluation, as it most likely that these are the types of barrels that this ammunition will most commonly be fired from. It is possible to obtain better accuracy from mil-spec/NATO pressure loads by firing them from an AR-15 that has a stainless steel match-grade barrel with a hybrid chamber such as the Noveske NMmod0 chamber or the Wylde chamber for examples. You're not going to make a silk purse out of a sow’s ear doing this, but I’ve previously experienced up to a 20% improvement in accuracy by doing so.

    As previously mentioned, it is reported that MK318 was “optimized” for a 14 inch barrel, so it seemed only fitting to evaluate MK318 from a similar length barrel. The first test vehicle used in this accuracy evaluation was a 14.5” Colt M4A1 barrel. The barrel was free-floated with a Daniel Defense Omega rail. (I was not able to use the mirage-shade with this barrel, due to the original standard front sight base on it.) A previous accuracy evaluation of this M4A1 barrel demonstrated that this barrel is capable of excellent accuracy for a chrome-lined, NATO chambered barrel.




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    A control group fired from the M4A1 barrel using hand-loaded 62 grain Berger hollow-point projectiles had an extreme spread of 1.13”.


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    Three 10-shot groups of the MK318 were fired from the Colt M4A1 barrel from the previously described bench-rest set-up. The extreme spreads of those groups measured:

    2.91”
    3.22”
    2.70”

    for a 10-shot group average extreme spread of 2.94”. The three 10-shot groups were over-layed on each other using RSI Shooting Lab to form a 30-shot composite group. The mean radius of this composite group was 1.02”.


    The smallest 10-shot group of MK318 fired from the Colt M4A1 barrel is shown below.


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    The next test vehicle was a 16” Colt HBAR with a 1:9” twist. This is the same barrel found on the Colt 6721 Tactical Carbine. This barrel is one of the most accurate “out of the box” chrome-lined, NATO chambered barrels that I’ve evaluated. The barrel was free-floated with a LaRue Tactical handguard.


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    A 10-shot group from this barrel fired using hand-loaded Sierra 52 grain MatchKings had an extreme spread of 0.98”.


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    Three 10-shot groups of the MK318 fired from the Colt 6721 barrel produced the following extreme spreads:

    2.98”
    2.85”
    2.89”

    for a 10-shot group average extreme spread of 2.91”. These three groups were also over-layed on each other to produce a 30-shot composite group with a mean radius of 0.82”.


    The smallest 10-shot group of MK318 fired from the Colt 6721 barrel . . .


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    The third barrel used to evaluate the accuracy of MK318 was a 20” Colt HBAR with a 1:7” twist, chrome-lining and a NATO chamber. The barrel is free-floated with a PRI handguard.


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    A 10-shot group from this barrel fired using hand-loaded 55 grain Sierra BlitzKings had an extreme spread of 1.18”.


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    Three 10-shot groups of the MK318 fired from the 20” HBAR had extreme spreads of:

    2.70”
    2.49”
    3.24”

    for a 10-shot group average extreme spread of 2.81”. As before, the three 10-shot groups were over-layed on each other to form a 30-shot composite group that produced a mean radius of 0.91”.


    The smallest 10-shot group of MK318 fired from the 20” HBAR . . .


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    A summary of the results from this evaluation are shown below.


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    The table below compares the accuracy of MK318 Mod 0 with several other "mil-spec" loads.

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    ....
     
    Last edited: Jun 24, 2015
    Auxiliaryjohn likes this.
  6. jrs93accord

    jrs93accord

    6,167
    194
    Jul 10, 2005
    Pensacola, FL
    Since you are talking about a SHTF stash, I recommend a large supply of M193 and M855 for your specific AR. Spending more money of 77gr. ammo is not feasible for a SHTF stash. If you had a precision AR, that would be different. Here is what I have done, I have several thousands of rounds of M193 and M855. This is because, in a SHTF situation, these types of ammo are going to be best suited for a fight. M193 is devastating when it comes to body/tissue damage. It is a nasty round. M855 is great for stability in a 1/7 barrel and it penetrating properties. I makes a much cleaner wound that the M193. I have several hundreds of rounds of 77gr. OTM ammo for my precision ARs should they have to come into play where longer range accuracy matters.
     
  7. Molon

    Molon

    111
    20
    Aug 22, 2009

    It most certainly is feasible and it is exactly what myself and the shooters that I associate with have done in the past.






    M193 and M855 are two of the poorest choices a knowledgeable person can make for ammunition intended to be used for defending the life of himself and his loved ones. M193 and M855 are inferior in just about every meaningful category compared to the consistently superior performance of modern self-defense loads.






    Except for all the times when it isn’t “devastating”. The terminal ballistic properties of M193 (and M855) are highly variable and unreliable . . .






    Fackler, ML: “Literature Review”. Wound Ballistics Review; 5(2):40, Fall 2001



    “In 1980, I treated a soldier shot accidentally with an M16 M193 bullet from a distance of about ten feet. The bullet entered his left thigh and traveled obliquely upward. It exited after passing through about 11 inches of muscle.


    The man walked in to my clinic with no limp whatsoever: the entrance and exit holes were about 4 mm across, and punctate. X-ray films showed intact bones, no bullet fragments, and no evidence of significant tissue disruption caused by the bullet’s temporary cavity.


    The bullet path passed well lateral to the femoral vessels. He was back on duty in a few days. Devastating? Hardly. The wound profile of the M193 bullet (page 29 of the Emergency War Surgery—NATO Handbook, GPO, Washington, D.C., 1988) shows that most often the bullet travels about five inches through flesh before beginning significant yaw. But about 15% of the time, it travels much farther than that before yawing—in which case it causes even milder wounds, if it missed bones, guts, lung, and major blood vessels. In my experience and research, at least as many M16 users in Vietnam concluded that it produced unacceptably minimal, rather than “massive”, wounds.


    After viewing the wound profile, recall that the Vietnamese were small people, and generally very slim. Many M16 bullets passed through their torsos traveling mostly point forward, and caused minimal damage. Most shots piercing an extremity, even in the heavier-built Americans, unless they hit bone, caused no more damage than a 22 caliber rimfire bullet.”







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    M855 is not a barrier-blind load and its terminal ballistic properties after barriers are pathetic compared to modern barrier-blind loads. In fact, M855 performs no better after passing through automobile windshield safety-glass (the most difficult barrier test in the FBI Ballistic Test Protocol) than the 77 grain Sierra MatchKing loaded in MK262.


    M855 compared to MK262 after passing through auto-safety glass at a distance of 100 meters . . .

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    Courtesy of Dr. G.K. Roberts







    More false information.






    M855 fragmentation . . .

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    Courtesy of Dr Martin Fackler






    M193 fragmentation . . .

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    Courtesy of Dr Martin Fackler






    M855 wound profile . . .

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    M193 wound profile . . .

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    .....
     
    Last edited: Jun 24, 2015
  8. jrs93accord

    jrs93accord

    6,167
    194
    Jul 10, 2005
    Pensacola, FL
    Nice visual aids. Everyone is entitled to their own opinion. :supergrin: