One comment on “Barrel-Length Studies In 5.56 NATO Weapons

  1. I’d like to offer a little context for people who are new to preparedness and weapon selection.

    First – This article is a great study in the pressure curve / velocity curve related to the AR/M16/M4 platform. Not knocking it. They are very clear about what is the opinion of the author vs. facts presented in the data.

    One teensy issue with a line in the article though: “M855 bullets traveling below 2,500 FPS when impacting a target will not produce a lethal wound channel.” That is a misleading statement, although I get what they are driving at. A person without the background in firearms might not however. ( What they mean is that essentially the round will probably not fragment without hitting a bone in a target when the velocity falls below this threshold with the M855 round).

    If the statement in question were true, that would mean out of the M4 platform, one shot stops would not be possible past 125 yards (with M855). First hand accounts from soldiers returning from Afgan/Iraq would suggest otherwise. Optics such as the ACOG definitely increase the odds of successful drops past the 125 yd threshold (due to increased ability for well placed shots). Which goes into my point on context – that the lethality of any round is dependent first on shot placement.

    So when selecting a round and barrel length it’s not a matter of this round or that round is BAD or this or that barrel length is completely BAD, but as I had drilled repeatedly into me: “know the limits of your platform, know the limits of your round, and work within those limits”.

    (Short barrels (under 14.5″) have a job specific purpose – either due to confined spaces or concealment – that’s it (oh, and to look cool too). They are not ideal by any stretch, but they have their time and place. For SHTF general purpose Main Battle Rifle? We recommend having at least a 16″ barrel on your AR.

    The M855 is an ice-pick at ranges where the round drops below 2500 FPS? Ok, then – shot placement, shot placement, shot placement – which should be the daily prayer in the religion of combat marksmanship anyway.

    In regard to conclusions drawn about reliability – this post addresses, dwell time, pressure and extraction issues – even for SBRs: http://weaponsman.com/?p=20221

    My conclusions:

    1. The M855 round will get the job done: Is the M855 round best for shorter barrel ARs (or even regular length ARs at extended distances)? Not by a long shot. If it’s what you can afford and what you have, own it. Past 125 yards in an M4 – shot placement is key as they are going to be ice-pick wounds.

    2. If one absolutely HAS to have an AR pistol or AR SBR, having a round like the MK318 would be ideal. http://pistol-forum.com/archive/index.php/t-4344.html You can’t find it many places and when you can it’s an arm and a leg type cost. There are other rounds like Hornady’s TAP FPD and MK262 Mod 1 type rounds (77 grain).

    3. If you don’t have a lot of money to have 11 different ARs, have a 16″ barrel. They offer excellent reliability with respect to the weaponsman article referenced above and are still short enough to maneuver with in most circumstances.

    Just some friendly context to a very valid study.

    R&D out 🙂

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