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77-Grain .223 Round

Discussion in 'Rifle Country' started by LoneRider, Aug 7, 2009.

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  1. LoneRider

    LoneRider Member

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    I've heard the ballistics and stopping power of this weight of round comparing favorably to 55-Grain round. Does anyone have any experience with this variety of round?
     
  2. EdLaver

    EdLaver Member

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    These rounds are usually used in .223 bolt guns or loaded one at a time into AR15s. They won't fit into mags because they are longer. Plus you have to have a different twist ratio (1:8 or 1:7 I believe) and at least 20" to 24" barrel to get full potential.
     
  3. DMK

    DMK Member

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    You're thinking of 80gr+ match rounds. 77gr rounds will fit in a regular mag and fire just fine in semi or full auto, although you will need a 1/8 or 1/7 twist to use anything longer than a 75gr round.

    The military uses a 77gr round known as mk262, mostly for long range DMR type use and also for special forces and anti terrorist operations. It sees limited use, as most of the military forces use the 62gr m855 and will continue to do so for the foreseeable future.

    The 77gr mk262 is supposed to have better terminal effect than m193 or M855 and has better stability and longer range. It does use a match bullet though.

    http://www.globalsecurity.org/military/systems/munitions/mk262.htm

    http://www.gunsandammomag.com/cs/Satellite/IMO_GA/Story_C/Black+Hills+Mk+262+Mod+1

    mk262 is almost impossible to find in the civilian market. Regular 75gr HPBT "match" rounds should work almost as well for self defense use and in most cases can be fired from a 1/9 twist barrel. The mk262 is quite a bit hotter and therefore is faster than civilian match rounds although civilian match rounds should be slightly more accurate on average. One can also buy 75gr TAP from Hornady. There is a special LEO/govt version of this round which is more like the mk262, but with a 75gr bullet (it is loaded hotter than standard TAP and has a cannelure to prevent bullet setback).
     
    Last edited: Aug 7, 2009
  4. Big44mag

    Big44mag Member

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    I use the 77gr for target shooting in one of my ARs. They are max length, loaded to 2.260" and cycle just fine through the mag. I only target shoot with it since I can't hunt deer with a 223 in VA but it will definitely have more "stopping power" than a 55gr slug.

    The 80gr slugs MUST be loaded one at a time as they will NOT fit in a mag.

    EdLaver is correct that a faster twist rate is better suited for a 77gr slug, mine is a 1 in 8", 20" bull with a Cooley brake and will shoot dimes pretty much all day long at 100'
     
  5. Slamfire

    Slamfire Member

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    If you have the right barrel twist the 77 Sierra match king is an excellent shooting bullet. It will outshoot the old 55 grain bullet out to 600 yards.

    I had the chance to talk to some American vets of Iraqi. The 77 grain bullet has extended their engagement distance, and if the bullet tumbles, the stopping power on two legged targets is good.
     
  6. rcmodel

    rcmodel Member in memoriam

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    There are actually two 77 grain GI designated marksman / sniper loads.

    The MK262 Mod 0 uses a 77 grain Sierra Matchking.
    The MK262 Mod 1 uses the same weight bullet, but it has a cannelure to cause it to break in two and fragment as it tumbles for improved lethality.

    Both are much more accurate & deadly at long range then the 62 grain M855.

    rc
     
  7. jaholder1971

    jaholder1971 Member

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    The M855 _might_ have better penetration, but for accuracy and terminal performance, especially out of an M4, the 77 grain load slaps M193 and M855 around the room.

    IIRC, Mk262 came into being after reports from Afghanistan found that M855 coupled with the short barrel and colder conditions made the 62 grain bullet much too slow to tumble in soft tissue, resulting in icepick type wounds in BG's and poor performance. Not to mention that the M855 has about a 3MOA accuracy level, so long range shots get a little iffy. Mk262 tumbles at about any speed and is very, very accurate.
     
  8. W.E.G.

    W.E.G. Member

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  9. C-grunt

    C-grunt Member

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    I had these rounds in 05 for my DMR. They were accurate out to at least 600 meters and worked very well on targets out to 400 meters.
     
  10. KW

    KW Member

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    There were a couple presentations floating around with info regarding penetration. One showed M855, M193, M995, and Mk 262 through cars and such. This presentation showed the M855 as being able to penetrate more/thicker barriers then Mk262.

    Another one had gel shots after passing through a loaded AK mag, to simulate a bad guy wearing a chest rig. In that one the M855 penetrated 8 inches of gel vs. just 4 for the Mk262 (and 11-12 for a 6.8 round).

    So the added accuracy and terminal effect on soft tissue of the Mk262 appears to come at the cost of barrier penetration vs M855.
     
  11. C-grunt

    C-grunt Member

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    I can see that. In my experience the M855 had pretty good penetration on vehicles and small structures.
     
  12. HorseSoldier

    HorseSoldier Member

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    Sort of. They share the same DODIC, even if they have different MOD #s.

    Both fragment well due to the OTM bullet format. The cannelure was added to make the loaded round more rugged for field use. I don't think any Mod 0 is still around -- we got a bunch of it when my last unit first fielded SPRs, but everything after that was Mod 1. Don't recall the team guys noting any change in performance for better or worse training or downrange when we switched over.
     
  13. LoneRider

    LoneRider Member

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    Are there heavier than 62 grain .223 rounds on the civilian market then? Basically I'm planning on purchasing a stock Remington R15 VTR for my DMR project and was wondering what the best type of .223 round would work best with it.

    I didn't realise the Army was adopting SPRs too. I've seen the M110 sniper rifle and my own unit had the modified M14s. I know the Marines are using MK.12s (my friend got one assigned to him and he was happy as anything, it even outperformed his beloved SAM-R).
     
  14. taliv

    taliv Moderator

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    what twist is it?
     
  15. DMK

    DMK Member

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  16. DMK

    DMK Member

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    The increased penetration of hard barriers is at least partially due to higher velocity. Interestingly, at close range, M193 penetrates hard barriers even better than M855, even though the latter has a steel core and the former does not.
     
    Last edited: Aug 8, 2009
  17. Onmilo

    Onmilo Member

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    MK262 uses a cannellure to prevent bullet setback into the case during full automatic fire, not to increase bullet break-up.

    It was found that MK262Mod0 would set-back leading to potential devastating weapon failure.
    The round was designed for optimal performance using a 1-7" twist and M4 extended feed ramps to help eliminate the possibility of bullet set-back and deformation.
    The cannellure was added after extensive testing.

    As stated, the 77 grain design was chosen because it was the maximum length bullet that would reliably feed through the magazine.

    The MK262 was design as a soft target/long range round.
    Should hardened targets be encountered at shorter ranges, it is advised to switch to M855 Penetrator rounds and both types of ammunition should be carried by the War Fighter.
    POA/POI is not greatly disimilar between the two rounds, optics and iron sights do not need to be rezeroed when alternating between cartridges though for maximum efficiency, combat zero should be adjusted using the MK262 round in the combat weapon.
    When encountering hardened targets at longer ranges, heavier weapons are employed up to and including airstrikes.

    Stocks of M193 ammunition remaining on hand are to be regulated to marksmanship training only and are not to be issued for use in combat operations.
     
  18. ParaElite

    ParaElite Member

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    When talking about tumbling. It should be about terminal ballistics not in flight ballistics. If the bullet tumbles in flight you ain't hitting ****. Just thought I would clarify! Thanks for clearing up the issue on the cannelure. The bovine excrement one hears on the misinformation_net is amazing!
     
  19. SpeedAKL

    SpeedAKL Member

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    Black Hills loads a Mk.262 clone 77-gr .223. I don't know of any other factory sources off the top of my head, but reloading is always an option. If you're going to shoot competitively, its a good choice.
     
  20. ChristopherG

    ChristopherG Member

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    The web-famed 'ammo oracle' at ar.15 has a good deal of interesting reading available on this and related topics. It's now organized into a menu-outline on the left of this page:

    http://ammo.ar15.com/ammo/
     
  21. DMK

    DMK Member

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    There is nothing wrong with M193. IMO it is better than M855 for civilian use, although not as good as 75-77gr HPBT.

    I'm not in the Army and don't need to care about their rules.

    Yes, the cannellure is there for that reason, but it is also a weak point in the bullet and does appear to encourage fragmentation. It was not put there for that reason, but it kills two birds with one stone, so to speak.
     
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