1:7 twist rate in ar15 ballistics

Could anyone help me with this. If I'm only shooting m193 out of a 20inch barrel ar15, the 1:7 twist, which would allow the bullet to spin faster on impact with a steel plate would allow higher penetration abilities due to the higher spin rate helping the bullet drill through the plate on impact. Against tissue, the 1:7 twist would allow the bullet itself to fracture and blow up sooner within the body due to the higher spin rate as compared to 1:9 or 1:12 twist, am I correct.
If this is true, for home defense the 1:7 twist out of a 20inch barrel would allow the most effectiveness from 55g m193 ammo in order to immediately drop a home intruder.

  1. 2 weeks ago
    Anonymous

    Only time I ever heard of twist rate impacting the effect on target is the 8.6 blackout Xtreme twist rate marketing which always came across as bullshit to me. Accuracy with proper twist rate for your ammo is far more important and if you want stopping power invest in better ammo and/or a longer barrel.

  2. 2 weeks ago
    Anonymous

    Twist rate does nothing until you start causing bullets to spin fast enough to break apart or not spin fast enough to stabilize

    • 2 weeks ago
      Anonymous

      Is that true? I feel like twist rate increasing rotational speed which increases the damage.

      • 2 weeks ago
        Anonymous

        This isn't anime bro. Your bullet isn't drilling its punching through.

      • 2 weeks ago
        Anonymous

        don't fall for the marketing drivel Q is putting out, its just 338 federal short

        • 2 weeks ago
          Anonymous

          K I wont. Thats what im asking, is it real or not.

          • 2 weeks ago
            Anonymous

            its not

            • 2 weeks ago
              Anonymous

              Thanks.

        • 2 weeks ago
          Anonymous

          Being 338 fed short isn't a negative. 6.5cm is 260 a bunch of things short. Doesn't make it any less good.

          • 2 weeks ago
            Anonymous

            >doing nothing new isn't a negative
            i guess? sidegrades aren't a negative
            the advantages of these same OAL but shorter case cartridges are extremely minimal
            you can (and eveyrone does) load the long efficient high BC bullets in the old cartridges. you have the same powder volume if you don't want the compress the load, the powder just rattles a little bit

      • 2 weeks ago
        Anonymous

        >I feel like twist rate increasing rotational speed which increases the damage
        Lolno you fucking retard
        This isn’t a fucking video game moron this is physics. shits only 55 grains and there’s only so much velocity you can squeeze out of the cartridge and you’re not going to get magic AP characteristics by making your light ass FMJ twist faster.
        Like, do you know how drilling metal works?
        When youre cutting/drilling mild steel like say with a drillpress your cutting tool needs to actually grip into the metal to create a clean cut and actually move material out of the way.
        I really don’t see how you’re going to accomplish that with basic bitch m193 you silly retard. and no you’re not going to be able to load up fucking drillbits.

  3. 2 weeks ago
    Anonymous

    1:7 twist is fine for m193, and no it does not imbue magical armor pen or bonus damage to flesh.

  4. 2 weeks ago
    Anonymous

    Forgot two points:
    5.56 out of any barrel is sufficient for home defence
    twist rate, if it were to have any noticeable effect on stopping power, would only increase expansion through centrifugal force on the bullet and thus reduce penetration, which is what the 8.6 blackcock marketing claims too and works out mechanically (just probably has an insignificant real world effect. A real world example of this phenomena is in high explosive anti tank warheads where if they're spin stabilized the armor-piercing effect is significantly diminished though the copper jet in a HEAT warhead acts a lot more fluid than a bullet. In addition if something will stop m193 then it'll probably stop m193 out of a longer barrel plus whatever magic you do to it. I say just accept that you won't go through a iii+ plate without extremely expensive 5.56 ammo or an ar-10 with ap. Not that I've looked into stopping that range of armor much. Just drill to cock/head shot as a followup if center of mass fails to drop.

  5. 2 weeks ago
    Anonymous

    Is that a black girl

    • 2 weeks ago
      Anonymous

      Would you impregnate her?

    • 2 weeks ago
      Anonymous

      No, probably Italian, not too many Black folks in the corps during ww2.

  6. 2 weeks ago
    Anonymous

    Physics major here. Any amount of spin on the bullet has EXTREMELY negligible effects on bullet fragmentation. Not to mention, most of the damage done by rifle bullets is caused by cavitation, not fragmentation. Its one of the reasons why they dont really make hollow point rifle rounds. The goal is linear velocity, not spin, not fragmentation, not necessarily even mass.

    • 2 weeks ago
      Anonymous

      they dont make as many hollow point rifle rounds because soft points are plenty to initiate expansion at rifle velocity
      they certainly do make hollow point rifle rounds though
      fragmentation is also a major cause of wounding for many rifle rounds
      the only thing youre right about is the twist rate isn't relevant

    • 2 weeks ago
      Anonymous

      No, because the fragmentation of m193 occurs not due to the spinning force of the projectile. It occurs because the bullet destabilizes and tries to fly sideways through the tissue, the lateral forces cause the projectile to break apart(typically starting at the cannelure). Because of this thequasi informed fuddlore is that lower twist rates which marginally stabilize the bullet, like a poorly thrown spiral with a football, make the projectile quicker and more reliable to fragment. Practically speaking there isn't much of a meaningful difference, fragmentation with m193 is still somewhat unreliable, so you're going to be putting 2-3rds on target as a matter of policy anyways. Reducing your chance of a late/no fragment situation from 15% to 10% doesn't change that(last number is out of my ass, first number is the real failure rate), and you aren't even controlling for the bigger variable of per lot/manufacturer projectile variations which will have a bigger influence anyways(namely jacket thickness). Go 1/7 and either don't worry about it or better yet use a better bullet.

      There's a bit of debate on it in the terminal ballistics community and I've seen decent indication of it having a non negligible roll fwiw. This is largely in regards to aiding projectile expansion particularly with soft points though, although it may play similar rolls with HP expansion and fragmentation. This is coming from some projectile manufacturers and SMEs like bitterroot bullets, Dr Roberts, and iirc Barnes. Overall I'm not exactly 100% sure myself which camp I'm in though.

  7. 2 weeks ago
    Anonymous

    penetration isn't achieved through a drilling effect. you can't drill anything with a flat point. I encourage you to try it if you don't believe me. drill a hole with a nail

  8. 2 weeks ago
    Anonymous

    >would allow higher penetration abilities due to the higher spin rate helping the bullet drill through the plate on impact.
    Pure fiction. A bullet is not a drill bit. It is both softer than the plate it is hitting and it has no flutes. There is no "drill" effect. If you want to get anal about it, a smoothbore would be slightly better because making the bullet spin takes some of its linear velocity away (conservation of energy). A smoothbore gun shoots faster muzzle velocity than a rifled one with all other factors being equal; this is why many tank cannons are smoothbore.

    >Against tissue, the 1:7 twist would allow the bullet itself to fracture and blow up sooner within the body due to the higher spin rate as compared to 1:9 or 1:12 twist, am I correct.
    That is theoretically possible, though it would be highly dependant on the bullet type. It's also not necessarily a good thing, bullets that expand or tumble too soon fail to penetrate deeply. I.e. a varmint bullet explodes in very shallow flesh as you can see from videos of people misting gophers, but if that wound is only 2" deep it's not going to do shit to stop an attacker or drop a large animal. Most likely there will be no real effect here outside of meme edge cases; over all the years I've been hunting with various firearms I've never noticed that twist rate had any effect on terminal ballistics.

    >If this is true, for home defense the 1:7 twist out of a 20inch barrel would allow the most effectiveness from 55g m193 ammo in order to immediately drop a home intruder.
    Statistically worrying about barrel lengths and ammo types for HD is a gigantic circlejerk; in real world statistics they all perform the same.

    • 2 weeks ago
      Anonymous

      >in real world statistics
      you have a statistically significant collection of data of home defense encounters with rifles with various ammo types and barrel length?

      • 2 weeks ago
        Anonymous

        Do you?

        • 2 weeks ago
          Anonymous

          no, i'm not the one claiming effectiveness is the same or different based on statistics

    • 2 weeks ago
      Anonymous

      >this is why tank barrels are smoothbore
      Only partially true

      You will squeak our marginally more velocity with a smoothbore compared to a rifles gun, but there are several more factors to consider.

      Shaped charge warheads do not perform nearly as well when spun up to a really high RPM via rifling.

      For kinetic penetrators, the trend has always been to produce faster, long-for-diameter projectiles that eventually ended up with modern APFSDS. When you make a projectile longer at the same diameter, you need to increase the rate of the rifling in order to achieve proper spin stabilization. With something as long and thin as a modern kinetic penetrator, conventional rifling could never have the twist rate needed to stabilize such a projectile - hence fin stabilized projectiles becoming the norm.

  9. 2 weeks ago
    Anonymous

    Normal person with a regularly functioning brain here, no you retard that's not how that works. I also don't understand why shooting through your walls and killing your dog/neighbor is desirable in a hd scenario

  10. 2 weeks ago
    Anonymous

    Isn't a faster twist worse vs. soft tissue or is that fuddlore? I recall hearing that 55gr 1:12 was so devastating because it's borderline stable

    • 2 weeks ago
      Anonymous

      It does not affect that at all. Twist rate stabilizes a bullet of a particular weight. That is it

  11. 2 weeks ago
    Anonymous

    1:12 causes key-holing with modern ammo from my understanding of Paul Harrell's video comparing twist rates. Which depending on your intentions could be seen as more damage on an unarmored target, but is a decrease in accuracy for anything besides close proximity use.

    • 2 weeks ago
      Anonymous

      >anything besides close proximity use.
      i.e. it's fine for home defense. I run 75gr OTM out my Colt SP1, it's still not keyholeing at 100 yds, though the accuracy isn't great so it's probably precessing. Fine accuracy for home defense, and will make a mess out of whatever it hits.

  12. 2 weeks ago
    Anonymous

    I read in a biography that back in Vietnam the spec ops fellas would always go for the highest twist rate possible with their run barrels. You want as much centrifugal force spinning into the target to dump extra spin energy into critical organs and cause greater numbers of fractal rotary expansion wounds.

  13. 2 weeks ago
    Anonymous

    General rule of thumb for 223/556
    43gr 1:9 -> 1:12
    55gr 1:7 -> 1:12
    62gr 1:7 -> 1:9
    77gr 1:7 -> 1:8
    Fight over 77gr if you want idc

  14. 2 weeks ago
    Anonymous

    If anything, slower twist like 1:12 would penetrate better because you would get faster velocity.

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