1:10 twist is ideal for .223 55 gr to 69 gr
My .223 R8 barrel is a factory Blaser barrel.
My reservations may be outdated, but there were enough horror stories with aftermarket R8 barrels a few years ago to keep me from buying one. This may have been solved (?)...
I believe that common wisdom is that 1:10 twist rate is the sweet spot for anything between 55 and 69 gr (see Guns & Ammo article inserted here under).
My own experience...
Because my purpose was not hunting but training, I was more interested in ammo cost and availability than in 1/2 MOA accuracy and heavy bullets.
My assessment that the factory Blaser barrel would work for me proved correct.
I initially shot really cheap 55 gr American Eagle bulk .223 ($0.40/shot). These did good enough, hovering around 1 MOA, for my purpose: high volume training out to 300 yards on a 6" plate.
55 gr American Eagle bulk .223 at 100 yards.
Not spectacular, but OK, especially considering the price ($0.40/shot).
Blaser R8 on tripod practice: .223 on a 6" plate out to 300 yards. The 55 gr .223 trajectory requires correction at that distance. Laser rangefinder and ballistic turret allow you to concentrate on shooting form. I you miss, it is not the rifle, the ammo, or the scope, it is you...
(Note: I since replaced the tripod with quad sticks. It shrank my groups by half a MOA).
I then tried, out of curiosity, other relatively inexpensive ammo, in various weights (55 gr, 62 gr, 69 gr), and, just to see, even expensive Federal Gold Medal Sierra MatchKing, 223 Rem, 69 Grain, Sierra Matchking Boat-Tail Hollow Point.
I found no discernible differences in accuracy due to bullet weight in the 55 gr to 69 gr bracket. Some brands shot better than others, but everything more or less stayed around 1 MOA, with two notable exceptions. The Hornady Frontier Cartridge Military Grade 223 Remington Ammo 55 Grain Hornady Match Jacketed Hollow Point ($0.60/shot) holds darn near 1/2 MOA in my factory Blaser R8 barrel; and the Federal Gold Match ($2.05/shot) holds more consistent true 1/2 MOA, but at 3.5 times the cost !!!
No contests for my purpose: it is worth -- to me -- to pay an additional $0.20 per shot over American Eagle to shrink the group to ~1/2 MOA, but it is not to pay an additional $1.65 per shot to eliminate the one "flier" that lands 1/4" away from the main group, seemingly in every 5 shot string. If I was competing it would be different, but for training, this is good enough
Hornady Frontier Cartridge Military Grade 223 Remington Ammo 55 Grain Hornady Match Jacketed Hollow Point in factory Blaser R8 barrel at 100 yards: not quite 1/2 MOA, but close enough for training purpose, and outstanding value at $0.60/shot.
If it is really important to you Bryan, I can get a box of 70 gr TSX ammo and see how they shoot in my barrel. In my mind, relating to 1:10 twist, the question is more about bullet length (typical issue in heavy for caliber TSX) than weight.
I notice that Barnes also loads a 62 gr TSX. That could be the ticket if the 70 gr does not group well in 1:10 twist.
Guns & Ammo article - Pairing Barrel Twist Rates with Bullet Weights for .223 and 5.56 NATO
gunsandammo.com/editorial/pair-barrel-twist-rates-ammo/249744
Conventional wisdom says slower twist rates wouldn't properly stabilize a heavy bullet. On the other hand, faster rates could over-stabilize lighter bullets. This is correct in theory, however, modern ballisticians have all but debunked the over-stabilization theory. All things being equal, it is better to have too much twist than not enough.
November 01, 2019
Keith Wood
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 debunked 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 err on the side of faster-twist — 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 Inches Twist Rate
You'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 your needs —
Winchester's 45-grain JHP load is a screamer at 3,600 feet per second.
1-in-12 Inches Twist Rate
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 Twist Rate
My first centerfire 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 MatchKing 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 Twist Rate
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 handloads using the 70-grain Barnes TSX - unless the bullet is pushed to maximum velocity. With longer barrels and commensurate faster velocities, this twist can be more forgiving.
1-in-8 Inches Twist Rate
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 Inches Twist Rate
This is the twist chosen by the military since the switch was made to the M16A2 — and the 62-grain 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- 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.
Keith Wood
Keith Wood is a New York Times bestselling writer, and Co-Author of UNAFRAID: Starting Down Terror as a Navy SEAL and Single Dad. Keith is an avid shooter, handloader, gun collector, and custom gunmaker and has been hunting big game and upland birds for three decades. Keith has been an outdoor writer since 2007 and has penned hundreds of articles for various publications. He is the Field Editor of Guns & Ammo and a regular contributor to Hunting, Rifleshooter, and Handguns. He's also an attorney and government affairs professional. He holds a BA in Political Science from Stetson University and a JD from The Florida State University College of Law. A native of Florida, he and his family reside in Alabama.
