Heavy subsonic 556 ammo

Discussion in 'Class 3 / NFA' started by Eli, Apr 9, 2016.

  1. Eli New Member

    Member Since:
    Apr 8, 2016
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    Just bought a MVP Patrol. Looks like it might be good gun to use with a can but the 1 in 9 twist maybe be a problem. For that matter how heavy can I go sub or supersonic? Everything else I own is 1 in 7 so this hasn't been a question before.
  2. Keith Moderator

    Member Since:
    Dec 7, 2014
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    The twist is a general purpose one but you'll be limited on the weight you can go compared to the 1:7. I have info on how heavy you can go at home, so I'll try to remember to post it up for you later. The plus side is that you can go lighter than what the 1:7 will allow.

    As far as the subsonic and can issue, I don't know enough to give a good answer. There a couple other members here that will be able to help you out with that when they happen to logon to the forum.


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  3. spamassassin Well-Known Member

    Member Since:
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    Only really light bullets (under 70 grains) will stabilize at subsonic speeds on a 9 twist with .223. If you had a 1:7 twist you could get up around 82-85 grain pills stable at 1080fps.

    NOTE: .223 was never meant to be used subsonic. All of the greatest parts of terminal performance of a .223 is at mach 2+. I don't know of anyone that does run subs in one. Running a suppressor is one reason filled with logic to try but it's also not going to do a lot of good. Power is diminished dramatically. If you want subs then you could find yourself a .300blk OR try the following option:

    Get a .22lr chamber adapter and some of the following. From experience they're going to deliver what you were going to get from a subsonic .223 but they're not a custom handload and you can get them for $.14:rd or better.
    https://www.midwayusa.com/product/2...nition-22-long-rifle-60-grain-lead-round-nose

    If you really want subsonic you gotta know that it'll do bad things to your trajectory and maximum range and energy delivery. The SSS rounds were made to be used in AR's and other .223 rifles. Through even a soda bottle suppressor they're super quiet.
  4. Keith Moderator

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    Here is the information on bullet weight and twist rate:

    [IMG]

    How to Pair Barrel Twist Rates with Bullets



    When the U.S. military first adopted the M16 rifle in the 1960s, the M193 cartridge and its 55-grain bullet was standard. The earliest issued variations of Eugene Stoner’s “Black Rifle” came with relatively slow rifling twist rates of 1-in-14 inches. Shortly thereafter, nearly all M16s and M16A1s were being issued with faster 1-in-12-inch twist barrels.
    In more modern times, bullets for military and civilian use have migrated to longer, heavier designs and twist rates have been altered to stay in-sync with this progression. With so many bullets and twist rates available these days, keeping track of which ammunition is compatible with your barrel can be overwhelming.
    Before we get into the weeds on individual twist rates, let’s take a minute to discuss rifling in general. “Rifling” are the lands and grooves impregnated into the barrel’s interior that impart spin on a projectile as it travels down the bore. This spin stabilizes the bullet in flight, much the way a football is “spiraled” by a quarterback.
    Determining proper twist is a factor of bore diameter, velocity, bullet weight and even bullet construction. There is no “golden” twist rate for all firearms. Civil war muskets such as the 1861 Springfield used extremely slow twist rates (1-in-78”) to fire heavy lead bullets with relatively good accuracy, while modern AR-15-style rifles use barrels as fast as 1-in-7 to stabilize long-for-caliber projectiles.
    Conventional wisdom taught us that slower twist rates wouldn’t properly-stabilize a bullet, causing it to yaw. On the other hand, faster rates could over-stabilize lighter bullets, causing similar problems. This is correct in theory—however, modern ballisticians have pretty much de-bunked the over-stabilization theory as a practical matter. All things being equal, it is better to have too much twist than not enough.
    Don’t misunderstand me; serious disparities in bullet weight to twist rate can cause poor accuracy, decrease velocity and potentially compromise a weak bullet’s structural integrity. I’d just prefer to air on the side of faster-twist barrels—especially with carbine-length barrels.
    Over the past decade or so, military rifles chambered in 5.56mm have migrated in two directions:
    1. Shorter guns such as 10.5-inch carbines emerged as the fight put troops in and out of vehicles and into close-quarter fighting.
    2. Accurized, Special Purpose Rifles (SPRs) were issued to fill the long-range overwatch niche between standard carbines and specialized sniper rifles.
    In both cases, heavy bullets evolved as solutions for terminal and external ballistic issues. Shorter guns needed the added bullet mass to compensate for lost velocity, while the SPRs used heavier, high ballistic-coefficient bullets to gain long-range performance.
    The two bullets that rose to the top of the heap were the Sierra 77-grain BTHP/OTM and the Barnes 70-grain TSX “Brown Tip.” Both bullets are excellent at their intended tasks and neither will perform appropriately in the slower-twist barrels that were standard for decades.
    Let’s take a look at the commonly-available twist rates used in-conjunction with the 5.56mm NATO/.223 Remington chambering.


    1-in-14 InchesYou’re unlikely to find a 1-in-14 barrel on any AR-15 produced in recent years, but they do exist and you may encounter them on a bolt action rifle on occasion. This is the least-versatile twist rate you’ll see in the 5.56x45mm/.223 Remington chambering. Although 1-in-14 barrels can stabilize 55-grain bullets used by the original M16, it’s really better suited for bullets up to 50- and 52-grains—most of which fall into the varmint and target category. If achieving maximum velocity with light bullets is your goal, this may fit for your needs—Winchester’s 45-grain JHP load is a screamer at 3,600 feet per second.
    1-in-12 Inches
    This is the slowest twist still seen in large numbers on AR-15s and other .223s. Though far better than the 1-in-14 twist, it is still unsuited for some of the premium loads developed over the past decade. Conventional wisdom suggests this twist rate is perfect for bullets in the 55-to 60-grain range, though most will stabilize the common 62-grain FMJ rounds. If you hunt prairie dogs or coyotes with lightweight .223 bullets, this twist rate will do fine for your needs. Doubletap’s 55-grain Nosler Ballistic Tip load generates 3,300 feet per second of velocity out of a 22-inch barrel, and will easily stabilize in this twist rate.
    1-in-10 Inches
    My first center fire rifle was a Ruger Mini-14 with a 1-in-10 twist. This is a good twist rate for lighter bullets and will also generally stabilize projectiles up to 69 grains, such as Federal Premium’s Sierra Match King BTHP load. If you’re happy with 55- and 62-grain FMJ bullets, you don’t need any more twist than this. In my mind, however, the 1-in-10 twist is just a bit too restrictive.
    1-in-9 Inches
    This is the beginning of the road for the shooter wanting to take advantage of the heavy bullet trend. The 1-in-9 is a great compromise twist rate—not too fast to cause problems with the 55-grain Bullets, but fast enough to stabilize all but the heaviest bullets under most circumstances. This twist will stabilize most traditional bullets up to 75-grains, and monolithics up to 70-grains—but they do so right at the edge of the envelope so not all rifles will do it. My personal 16-inch Rock River Arms carbine with a 1-in-9 twist does fine with ASYM’s Tactical Match Grade 77-grain OTM load, but has shown signs of instability with hand loads using the 70-grain Barnes TSX—unless the bullet is pushed to maximum velocity. With longer barrels and the commensurate faster velocities, this twist can be more forgiving.
    1-in-8 Inches
    For a 16-inch general-use carbine, the 1-in-8 twist is about as versatile as it gets. This twist rate will comfortably stabilize bullets up to 80-grains, and the excellent 75- and 77-grain bullets also work great at a wider spectrum of velocities—which means barrel length isn’t critical. My 3-gun rifle, built by my friend Iain Harrison, wears an 18-inch, 1-in-8 twist White Oak Armament barrel and shoots just about anything well.
    1-in-7 InchesThis is the twist chosen by the military since the switch was made to the M16A2—and the 62gr. M855 cartridge—in the 1980s. This twist is found on the M4 carbine, the M16A4, the Mk12 Special Purpose Rifle and even the HK416. Its ability to stabilize tracer rounds in-flight is one of the reasons that the military chose this twist rate.
    This barrel will stabilize bullets of up to 90 grains, and can handle the 70- to 77-grain bullets at just about any velocity, which makes it well suited for carbines with very short barrels. If you want a Mil-Spec clone, the 1-in-7 twist is the way to go.
    I currently own two AR-15s with 1-in-7 twist rates—a 10.3-inch Mk18 Mod. 1 and an 18-inch Mk12 Mod. 1—both made by Monty LeClair at Centurion Arms. To illustrate how velocity and twist rates can be the ying and the yang of bullet stability and accuracy, I fired a variety of loads side-by-side from the two rifles. The 10.3-inch SBR shoots anything from 55-grain FMJ to 77-grain OTM with excellent accuracy, while the 18-inch Mk12 is scary accurate with the 70-, 75- and 77-grain bullets—but won’t shoot 55-grain or 62-grain FMJs worth a damn.
    Matching the rifling twist in your rifle or carbine to the appropriate ammunition won’t guarantee great accuracy, but it will ensure the bullet is properly stabilized in flight. On the other hand, using a bullet that’s too heavy for your barrel’s twist is a virtual promise of poor accuracy and ineffective terminal performance. If you’re struggling with the accuracy of your modern sporting rifle, be sure you’ve properly matched your ammunition to the barrel’s twist.
    Ulfberht likes this.
  5. Eli New Member

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    Apr 8, 2016
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    Thank you for your responses: With regard to the .22lr the internet "experts" don't seem to recommend the use of "dirty" .22lr in a .223 can. I don't see 2 cans in my future but I can't say I'm convinced I won't try it. Neither do I see a .22lr SBR in my future. With regard to the 18 inch 1:7 inch barrel: Somebody once said happiness is when your expectations are met. If I had a 18 inch 1:7 that didn't shoot 62-grain FMJ "worth a damn" I wouldn't be happy especially if I had a 10.3 inch from the same manufacturer that did. Although clearly I have different accuracy expectations of a SBR. In my case that includes the effective use of Hornady 55 grain TAP in short barrels. That being said Hornady 75 grain TAP is clearly outside the circle for the 1:9 MVP but while it might be outside your expectations of accuracy it might not be outside of mine at 100 yards or less which aren't that high. There is no prairie dog hunting in my future but I might be better off throwing rocks with that heavy a bullet in the MVP LOL.

    I don't have high expectations of subsonic .223 either. If it comes close to the advertised power of a .380 I may be ok with that. The question is it worth the price of the adapter to find out if the MVP handle a 77 grain at 100 yards or less? Not even sure if these are vaporware or actually something that exists.

    https://www.midwayusa.com/product/1...ain-hollow-point-boat-tail-subsonic-box-of-50

    https://www.cheaperthandirt.com/pro...0-fps-20-round-box-223sub75jhp-10223752000.do
  6. jwb47 Active Member

    Member Since:
    May 4, 2014
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    outlaw state has a 100 grain .224 bullet they claim it can go 2400 fps or be used for subs loaded to magazine length . they also state a 1/7 twist is needed . bullet length plays just as much of a factor as weight . I havent got that far with a 223 as far as subs are conserned although I do intend to give these bullets a try one of these days just because . for the record my mvp wont shoot 75 grain amax worth a crap but it will shoot 77 grain matchking's I just dont have a need for that heavy a bullet out of my mvp and reserve them for my 20 inch A4 rifle . for hunting I have really grown fond of the barnes 62 grain tsx and 60 grain hornady v-max .
  7. Keith Moderator

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    100 grains is a mighty long bullet for a .223. It would seem only a break open rifle would be the only thing that would be able to shoot it. That or the bullet get seated pretty darn deep.


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  8. spamassassin Well-Known Member

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    It'd be pretty spanky in a .220 swift or .22-250 or .223WSSM with an appropriate twist rate on the barrel. 3K fps kind of territory
  9. jwb47 Active Member

    Member Since:
    May 4, 2014
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    They claim the bullets can be fired out of an ar15 when loaded super sonic . Im gonna order some just because my curiosity has been tweeked . Im thinking maybe around 4.5 grains of trail boss for subs and super sonic im gonna have to do some research.
  10. spamassassin Well-Known Member

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    I'd look to N550 and similar burn-rate:density powders for the supersonic loads. It's been popular with guys trying to launch 90's at decent speeds. One note, it's reported to be pretty rough on barrels. It's going to need to be a pretty slow burning powder and a long barrel would be best.
  11. jreinke New Member

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    Jan 14, 2013
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    Quickload says that 3.8 grains of Trailboss will push a Speer 70 grain Semi-spritzer at 1094 fps from a 16.5" bbl.

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