Zediker Examines Long Range Shooting with AR-Platform Rifles
Looking to shoot an AR-platform rifle out past 500 yards? Then you should read two articles by AR guru Glen Zediker. Author of The New Competitive AR-15 and The Competitive AR15 Builders Guide, Zediker is an expert when it comes to AR-platform rifles. Glen believes ARs have excellent long-range capability, provided they are built to high standards, with good barrels.
Glen says: “a properly configured AR-15 is easily capable of good performance at 500+ yards. Good performance means it can hit a 1-foot-square target all the time. Competitive shooters can cut that standard in nearly half (the X-Ring on an MR1 600-yard NRA High Power Rifle target is 6 inches, and high X-counts are commonplace among more skilled shooters).”
Published in the Cheaper than Dirt Shooter’s Log, Zediker’s articles first cover the history of the AR-15, and then explain how AR-platform accuracy can be optimized. Part One reviews the AR’s development as an accurate firearm, tracing its evolution from a Vietnam-era combat weapon to what is now a favored target rifle of High Power competitors. READ PART ONE.
Part Two discusses the specifics that make an AR accurate at 500 yards and beyond. Zediker talks about barrel configuration (profile and twist rate), bullet selection, floating handguards, and proper mounting of optics or iron sights. READ PART TWO.
Here are some highlights from Long-Range AR-15 Part TWO:
Barrel Twist Rate
To stabilize anything longer than a 68- or 69-grain bullet, the barrel twist rate must be — at minimum– 1-in-8. Twist rates reflect how far the bullet travels along the lands or rifling to make one complete revolution. So, 1-in-8 (or 1-8, 1:8) means “one turn in eight inches.” I think it’s better to go a little faster in twist. There is nothing wrong with a 1:7 twist. The 90-grain bullets require a 1:6.5, and that is getting on the quick side. If you want to shoot Sierra 77s or equivalent, and certainly anything longer, 1:8 is necessary. By the way, it is bullet length, not weight, which constitutes the necessary twist rate to launch a stable bullet.Optics Mounting
Correct optical sight positioning can be a challenge. With a flattop upper, I need a good inch additional forward extension at the muzzle side of the upper for the sight mount bases to avoid holding my head “back” to get the optimal view through the scope. A longer rail piece is necessary for my builds as a result.Buttstock Length and Adjustment
An adjustable buttstock is valuable, and even more valuable if it’s well-designed. Mostly, a standard stock is too short, and the cheek area sits too low. Adding length helps a lot by itself. There are assemblies that replace the standard buttplate to allow for length and, usually, height and rotation adjustments for the buttpad. An elevation-adjustable cheekpiece is a big help to attain a solid position.
Similar Posts:
- Zediker Writes about Long Range Shooting with the AR-15
- Choosing Optimal Barrel Twist Rate — Tips from Glen Zediker
- Optimal Barrel Twist Rate — Factors to Consider
- Too Fast or Too Slow — What’s Your Optimal Twist Rate?
- How to Select Proper Twist Rate for Your Bullet Size
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Tags: .223 Rem, 5.56, AR Upper, AR-15, AR10, AR15, Glen Zediker, Long-Range, Lower Receiver
Zediker,
Has the most annoying writing style of any author I have ever come across. Very knowledgeable just a very awkward read.
Paul
Paul,
Zediker has a conversational style, which I enjoy reading. He also covers a lot of information with not a lot of words. What do you find annoying about his writing?
Charlie
Beyond 750 yards 223/556 is hard to place an accurate shot in any kind of wind. Semi auto past 750 quickly becomes a battle of weather or not brass life and carbon buildup in the chamber is worth it. Ar10 platform 6.5 creedmoor sounds great till you realize what your doing to your brass and chamber.
You don’t need a 1:6.5 to stabilize the 90s. Have a 1:7 in both AR and palma rifle and they both stabilize 90gr SMKs nicely. 90gr VLDs will stabilize when its above 60deg.
Editor: Shawn, it’s good to hear you got the 90s to work in a 1:7″ twist barrel. However, Sierra states on its webpage: “This bullet requires a barrel twist rate of 1×6.5″ or faster”. So Zediker’s comment is consistent with the official factory recommendation. Stability is a function of both velocity and barrel twist rate, so it could be that slower loads need the 1:6.5.
Link: https://www.sierrabullets.com/store/product.cfm/sn/9290/224-dia-90-gr-HPBT-MatchKing
I like the AR platform. It’s amazing just how accurate they are compared to older semiautomatics. M-14’s don’t come close. One minute is about the best I have done wtih that platform. With a properly built AR 1/2 moa is easy. Definitely a big advancement in semiautomatic technology.
Editor, etc.,
It is true that Mr. Shawn has had some
decent success with 7-twist .223 rifles at 1,000. They work, but it is the additional tube length that makes the difference. We have had this discussion multiple times.
Being a Long Range Service Rifle shooter, I had no choice: it’s 20” long, or it’s not “Service”.
I can confirm that something on the order of 6.75 to 6.5” twist is REQUIRED for those bullets in a short tube. Being that Sierra originally intended the bullet for relatively short barrels, and their inherently conservative position as a manufacturer, I am behind their 6.5” recommendation.
The barrel I had was a Bartlein 8-6.5” progressive 5R. It worked, and even though it was a dedicated LR rifle (110 freebore at 0 rounds), it hammered quite well with “magazine” ammunition using the 77 SMK. Last I checked, the bearing surface of a 77 Sierra had nearly 1/4” between it and the lands, but I estimate the accuracy potential of the rifle as 1/2 minute at 300 yards. At 100…well, I could surely win a pile of $5 bills with it.
My point in that is that a guy shouldn’t be AFRAID of a fast-er twist .223 barrel, as it will shoot shorter bullets fine as well. If you want to try 90’s, do it.
In ideal conditions, even a 7.7” twist 20” can work at 1,000, but it requires you to push 80’s fast enough you are really risking case integrity. (though I did not try it with 2000MR, as it didn’t exist yet. That powder can go fassssst.)
But on my original point, the 8-10” difference between Shawn’s baby-Palma and my SR is EVERYTHING if you think a 7-twist is fine.
As to his success with the 7-twist Service gun: it is despite the barrel, not because of it, and I haven’t seen him shoot it much at 1,000, either.
at Shawn..hehehe..
At the end of the day, even if you had a 26” “Spacegun” for the 90’s, it’s never going to be competitive at the long lines against even something as mild as a .308 bolt gun in the same length. It’s just not a thing, despite the occasional successful shooter like Bob Gill. Lots (lots) of extremely experienced shooters think the same thing, and it’s for good reason.
For the purposes of Mr. Zedicker’s rifle, he is correct, at least as far as 600 yards is concerned. There are lots of us that can shoot rapid fire and keep the bullets on a 12” plate, and more than none that could do it on half that size. It’s a pretty effective rifle at that distance, with the “new” bullets.
But for LONG range, I cannot in good conscience recommend a 90-grain AR…or ANY AR” that doesn’t end in -10.
-Nate