Bullets and Barrel Twist


(From Four Guys Guns) The .223 and the 5.56×45 cartridge are some of the most commonly used rifle cartridges in the U.S. and the world today.  There are many similarities between the two but bear in mind you should REALLY know the differences.  I could write a really long and possibly dry article on all the intricacies, uses, history and dimensions, but this is not for re-loaders, competition shooters or experienced people.  You want the straight deal on what this means for you and your new rifle, and we can expand on knowledge from there.

Read the remainder of the article in its entirety.

10 Comments on "Bullets and Barrel Twist"

  1. I completely disagree with his assertion that you should stick with a 1:9" barrel until you know what you want to do with your rifle, especially an AR. The best barrels on the market are 1:7". I can't think of too many companies producing cold hammer forged 1:9" barrels that use the proper steel and are chrome lined down the entire bore with the proper 5.56 NATO chamber. I actually can't think of any, but perhaps there is someone.

    However, several companies manufacture or sell chrome lined, cold hammer forged barrels in a variety of lengths and gas systems. They'll last twenty thousand rounds likely a lot more and you'll be able to shoot everything from 40gr varmint loads to the 70gr Barnes TSX and 77gr Sierra Matchking. I've never heard of jacket separation happening when shooting lighter bullets in 1:7" barrels. I've shot thousands upon thousands of rounds of M193 through 1:7" barrels without issue. So have many others.

  2. Not a bad article, but it missed a bunch of key points. The differences in the chamber & throat between .223 Remington and 5.56×45 are enough to cause difficulties. Here's my takeaway based on a lot of reading: Shooting 5.56 ammo in a .223 rifle, especially one that is chambered on the tight side of the specs, and has a short leade (throat), can cause chamber pressures to rise significantly.

    The classic indicator of this is "popped" primers – primers that are ejected from the case. By any stretch of the imagination, this is a sign of very high pressures. In an AR-15, the loose primer can fall into the trigger group and lock it up. The high chamber pressures also can cause accelerated wear on the bolt.

    Most importantly, ammunition manufacturers know all about this and have chosen the same strategy – they don't sell most of their 5.56×45 ammunition to the retail public out of liability concerns. Federal, Speer, Hornady, Winchester and Black Hills all sell 5.56 ammo to law enforcement, but you'd be hard pressed to find much of it on store shelves except for the commodity FMJ.

    One final note – many retail AR15s don't actually have a 5.56×45 chamber, even if the lower receiver says so. They frequently have a .223 Wylde chamber, a kind of hybrid between .223 Remington and 5.56 NATO. Unfortunately, that doesn't solve all the problems.

  3. 1. You lost me at knockdown power.
    2. Projo bearing surface length and velocity, not weight determines proper barrel twist

  4. Its easy If you want to shoot military ammo either M-193 or M-855 mk-262 ect use 1/7 twist is the best. If you want to hunt and use varmiter bullets a 1/12 or 1/9 will suit you well just think of what you want and do with your weapon to help make a pic.

  5. Johnny Quest | May 22, 2012 at 1:51 pm | Reply

    *** was that article? Let's start with the manufacturers he mentions:

    "Bushmaster, Stag, DPMS, Colt etc…"

    Only one mentioned is worth a crap, Colt, the rest are junk. That right there is the red flag on any advice from the Four Guys. I don't recall reading a more poorly written article containing so much inaccurate information in only a few paragraphs.

    Although Colt does offer the 6721 with a 1:9 twist barrel, I don't think it is a huge seller. There is no reason to get a 1:9 with most ammunition going to longer (heavier) bullets, so 1:7 is it daddio.

    I think I will stick with Five Guys Burgers and not revisit Four Guys Guns. Don't want to make the mistakes THEY are making.

  6. Considering a Colt LE6920 is only a hundred or two hundred dollars more expensive than a Rock River or Stag turd, it's really not a big stretch. Especially when people that buy a Stag and then hang a ton of crap off of it that they don't really have a need for, but just buy because it looks cool.

    If it were me, buying my first AR, I'd just build or have built a quality lower with a mil-spec components along with the grip (not an A2 fan) and stock of my choice. Then I'd buy a BCM 14.5" mid-length with a CHF barrel and a bolt carrier group. Add in a single point or combat two-point sling of choice and a T1.

  7. I do say most tactical ammo also is set up for 1/7 twist to go with ARs as well.

  8. A major item the entire article misses is that the LENGTH of the projectile matters the most in twist rate stabilization, not the weight. Reference Brandon Webb's 21st Century Sniper if you disagree. In the case of 5.56 rounds, most of the heavier rounds are also longer, so a mostly moot point in this case, but it is too bad many shooters are misdirected on the core point of this matter.

  9. Thank you to JTMedic, will read up! You get it sir.

  10. Actually the length to diameter ratio is most important. The weight plays in only indirectly. It's just a happy accident that heavier bullets are longer than light ones.

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