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.

{ 22 comments… read them below or add one }

NMate May 22, 2012 at 4:50 am

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.

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Josh May 22, 2012 at 6:17 am

NMate,
Sig produces a chrome lined 1:9 on all of their AR's it is getting more and more common. I own one with about 10,000 rounds through it and have had no issues with jacket separation. When going with a barrel that is 1:9 it increases stability for higher grain bullets allowing for a more diverse range that can be shot with your rifle. I see their point, valid or not it is certainly like asking someone how much horse power you should have in your car, there are other things to consider. Looks like a good place to start for beginners.

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B1148 May 22, 2012 at 8:02 am

NMate is right on the money. 1:7 twist WILL NOT cause jacket separation or significant accuracy loss with your common 55gr loads. 1:7 is also more versatile allowing you to shoot the much longer 77gr bullets. Bullet length, not weight (although naturally longer bullets will be heavier) is the determining factor for optimal twist rate.

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NMate May 22, 2012 at 5:19 pm

1:9" will lessen the stability of heavy bullets in comparison to the 1:7" twist rate. I don't know what the upper limit for 1:9" rifling is with the 5.56 NATO/.223 Remington, but I doubt it's much more than 64gr. Once you hit 70gr, you need at least 1:8" rifling, preferably 1:7". 1:9" won't allow you to accurately shoot the 70gr TSX or the 77gr SMK loadings that are out there.

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Davey May 22, 2012 at 5:54 am

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.

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Whitey May 22, 2012 at 6:31 am

@Davey, Thank you for the "Popped Primers" information. I never knew that and to me, that is some great information to have. Comments like yours are exactly what we look for on our page to inform new shooters without belittling them.

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JTMedic83 May 22, 2012 at 5:03 pm

@Whitey
Here's some info about buying AR's
It's skewed slightly toward the LE community, but it's information is still great.

It covers:
Barrels (chrome lining, twists, 5.56 vs .223, variations in feed ramps, and magnetic particle testing, Free Floating vs Non-Free Floating)
Mil-Spec vs Commercial
Gas Systems
Upper Receivers (A1, A2, and A3)

They also go into all the other little things like grips, lights, optics, flash suppressors, stocks, hand guards, and slings.

These things may help you with future posts.

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JTMedic83 May 22, 2012 at 5:04 pm
Johnny Quest May 22, 2012 at 5:23 pm

Just an FYI, http://m4carbine.net/ is far and away the best site out there. Use the search feature and you will find a plethora of information on anything you heart desires relative to the AR/M series of rifles.

Arrrgh May 22, 2012 at 6:35 am

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

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Lance May 22, 2012 at 8:12 am

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.

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Johnny Quest May 22, 2012 at 1:51 pm

*** 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.

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JTMedic83 May 22, 2012 at 4:54 pm

As Whitey, the four guys rep, mentioned… this information is geared towards new shooters… aka commercial, weekend hunters/ warriors… people just getting started.

The manufactures he mentioned are just what their target audience is going to be buying, why? Cause their just looking for fun, they're not operators. They're not gonna drop a grand or so on a LWRC or what not.

Yes the information isn't totally accurate… but don't rip them apart. Correct them, help them, and guide them.

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Johnny Quest May 22, 2012 at 5:13 pm

I disagree. If you are going to put out information in a public forum for consumption by whomever, it should be accurate irrespective of the audience, particularly when representing yourself as an authority. Politics and politicians come to mind when the opposite is true more often than not.

That being the case, the guys putting stuff on this blog should better vet the subject matter and sources minimizing garbage like this article. My .02

One more thing, you can get a Colt that meets the TDP for under $1000, only a couple of hundred more than some the junk he lumped in there. If you can't swing the extra couple hundred buck for a good rifle, collect marbles.

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NMate May 22, 2012 at 5:23 pm

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.

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JTMedic83 May 22, 2012 at 5:47 pm

True… to a point.

While my M4 is probably about $1800 because I use it and I need to rely on it. I found a DPMS for a little over $500 used for my kid… why? It's all he needs right now at 10.
We take it out to the back acreage and shoot watermelons, pumpkins, beer cans, paper plates… whatever. He's not hanging lights, optics, AN/PEQ-15's, or whatnot.

He doesn't even need a single point… heck it's would just drag the barrel across the ground at his height. Just a simple 5 dollar basic sling.

If I didn't have the knowledge I have, and I was just a regular soccer dad… I sure as heck would want to know that there is a deference between .223 and 5.56

When he gets older and wants a better rifle guess what, then he'll learn to save for one. But for now a $500 1:9 twist is just fine for him.

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Johnny Quest May 23, 2012 at 3:59 am

JT,

I understand your reasoning, just not what I would do. By quality and buy once. In your sons case, IF he had say a Colt 6920, or say BCM, DD , you would have a second rifle if needed and he won't have to buy another when he gets a bit older. Just a different point of view

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Lance May 22, 2012 at 7:50 pm

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

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jagersmith May 22, 2012 at 9:26 pm

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.

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Whitey May 22, 2012 at 9:26 pm

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

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Markk May 24, 2012 at 12:39 pm

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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Bob January 22, 2014 at 11:00 pm

Inside of 200 yards what does it matter…If you want a sniper rifle buy a sniper rifle…AR15s are just a plinker….

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