Campbell on AR Accuracy: Why Does My ArmaLite Shoot So Tight? Or, What If It Doesn’t?
By R.K. Campbell

Why does the ArmaLite rifle platform shoot so well? My son owns a Bushmaster carbine that he has tightened but slightly with the little red block and he has also fitted a good ATN scope with illuminated reticule. The 16 inch barrel carbine shoots far better than it has any right to. My personal Bushmaster is a good shooter and the Daniel Defense rifle even better. As far as accuracy goes nothing in the arsenal touches the AR when it comes to off the rack military rifles. And I own a number of pretty decent blue steel and walnut rifles. I do own other .223 caliber rifles. As an example, recently I was firing my 24 inch heavy barrel bolt gun in a leisurely session. The Howa 1500 is simply an excellent all around rifle. This bolt action rifle is fitted with a 20 power Nikon optical sight. The piece will consistently group the Fiocchi 55 grain JSP loading into a three shot group of about .4 inch at 100 yards. With the off the shelf ‘canned heat’ FMJ loads offered by Fiocchi, the Howa never strays over an inch for three shots at 100 yards. The pretty little Remington 799 is not nearly as consistent with its lightweight sporting barrel. The Bushmaster plugs along with three shot one inch groups with some loads and a bit larger with others. Will a coyote know the difference? Of course not.

I am well aware that we are all about the pursuit of accuracy, accuracy being perfection and the best example of accuracy being zero deviation. A good marine chronometer is a device you can bet your life on and so is an accurate AR rifle, but the reason the AR is so accurate is not often understood. There is a great difference in the accuracy potential between the AK47 and the AR-15, largely because these two adversaries are of a different generation. The AR was designed in a way that it can be built in small shops while the AK was built for mass manufacture. The design of the AR-15 rifle lends itself well to accurizing, and accurizing is simpler and less demanding of time and skill than improving the bolt gun. But you can take the AR and defend your life against a take-over robbery or armed gang, or even deliver fast repeat shots on predators. The black rifle is a better all-arounder than we would have thought when it was first introduced.

While I admit a certain affinity for blue steel and walnut, the practical applications of a gun that is assembled rather than carefully hand fitted are obvious. The AR-15 rifle is assembled and the design is such that extremes of heat or cold or even firing the rifle until it is hot does not affect accuracy. The bolt locks solidly into the barrel time and again with each cycling of the action. The barrel does not depend upon free floating or any other consideration other than being locked into the receiver. Unlike quite a few sporting and military rifles, it is difficult to affect the zero of the AR by cleaning or even disassembly and reassembly. One of the Bushmasters was fitted with a Compass Lake trigger (Compasslake.com) some time ago. This is one of the few improvements really needed to spruce up AR-15 accuracy. Good ammunition is essential. While I have spent a few hours on the bench with Forster precision dies for the .223 – and noticed the improvement in accuracy by careful load practice – there are a number of excellent factory loads that truly deliver. One of these is the Fiocchi load previously mentioned. Most of the bolt guns are still rifles for varmint weight bullets and the heavy bullets tend to be darned accurate in a quality AR. The FMJ bullets are plenty accurate for meaningful practice. Remember, the bolt locks into the barrel, not the receiver. The locking lugs of the AR are well designed. The only ones I have seen broken are locking lugs that seem to have been flexed by use of a poorly designed forward gripping handle. This defect has flexed the barrel over time and allowed the bolts to hit a bit off center. The Daniel Defense forend is immune from this problem with its forward gripping handle. I do not really need the high tech Daniel Defense multi-function forend but the gun shoots great and the option is nice to have. And I have to admit this black tactical stuff grows on you after a while. Back to the lockup – there is no design that offers more consistent lockup than the AR-15 bolt design. And the lockup is consistent with each and every shot delivered from a bolt that tends to move back to the same position with little lateral or radial play.

Barrel twist rate is important to handloaders more than sport shooters, but should be understood, particularly when it comes to the AR-15 rifle and the wide choices in ammunition. Let’s consider a 1 in 9 inch turn. The barrel simply turns the bullet one complete revolution in nine inches. (The weight isn’t as important as the length but weight and length are pretty much linked except in the case of the Barnes bullets.) A fast twist can move the bullet around as fast as the water twists in a pail and work up a lot of heat. The 1 in 9 twist is good for the popular 69 grain bullets. I have also used the HSM loaded 80 grain bullet and this one is pretty darned accurate but really needs a 1 in 7 twist. So, study the likely needs before choosing the gun and twist. Varmint shooting or deer hunting? Personal defense? If you are a defensive shooter you darned well better use the heavy bullets; not the varmint bullets or the darned things will be blowing up on zippers and leather coats. The 1 in 7 is versatile and will handle all weights including the 80 grain pretty well. If you are a fan of the legendary Black Hills 77 grain Open Tip, the most proven Tango killers of all time, then you need the 1 in 7 barrel twist. Among the few problems likely is shooting the new breed of 36 grain bullets in the faster rifle barrel. In the 1 in 7 you may you may suffer a blown up bullet. A bullet coming apart isn’t actually a result of extreme velocity but rather a result of jacket damage from the too fast twist.

Sometimes we discuss the difference between the 5.56mm NATO and the .223 Remington cartridge. The difference is in the chambers, with the .223 Remington chamber the tighter of the two with a minimum lead. The NATO specification chamber is the more versatile and, in simple terms, the safer as far as pressure spikes go. In short, firing higher pressure 5.56mm loads in the short .223 chamber may raise pressure, period, and sometimes result in a blown primer. An AR-15 rifle really should have the 5.56mm NATO chamber and the piece will shoot admirably with this chamber. You really should understand this issue and be certain that you are feeding the rifle the proper loads. Again, this issue is more of a problem for handloaders. Now, sometimes a rifle doesn’t shoot as well as we would expect. There are cures for this problem as well. One of the major problems with AR rifle accuracy is fouling. Folks don’t like to clean their barrels and many assume that a jacketed bullet eliminates the necessity of frequent cleaning of the bore. Don’t laugh, I see this often. Sometimes the cleaning is done with a light oil and cotton only and no solvent. Use a cotton patch with the proper solvent and you can find the problem easily enough. I have yet to see a truly shot out barrel in an AR, although I am sure some exist. Fouled barrels are a dime a dozen. Clean the barrel and you just find that the groups will shrink. Another problem is a dent in the muzzle brake or on the crown. A good AR rifle isn’t inexpensive but just the same sometimes folks give them rough treatment. A rough crown is easily repaired. A combination of a rough crown and a fouled barrel will limit the useful accuracy of any rifle.

A rough trigger may be learned but an inconsistent trigger is murder. There are certain brands of ammunition that have earned a reputation for dirty powder and subsequently the AR’s get soaked with unburned powder. In fairness it isn’t all about the dirty ammunition. Some brands, such as Wolf, are so inexpensive we tend to fire prodigious amounts of this ammunition for fun. Of course the rifle gets dirty. You might fire only a hundred rounds of more expensive loads while you may burn up two or three hundred rounds of Wolf at one session – that is only 10 thirty-round magazines, just a start for some of the more interested shooters. At least that is my take on the situation and inexpensive ammunition that always goes bang is going to be in demand. In the case of the AR-15 rifle, the unburned powder and powder ash ends up in the trigger mechanism. The grit ends up creating a situation in which the trigger isn’t consistent. It will weigh so much with one press and so much with the next, which is pretty difficult to handle at anything except close range. Take a spray can of aerosol cleaner and blast the trigger action. The AR is tailor made for such down and dirty cleaning. Get out the cleaning kit and do the business next, sure, but begin with spraying the action clear and you will see an immediate improvement in the trigger action. There are a few little tricks to the AR-15 rifle that will result in a long life, an accurate rifle and good shooting. Just be certain the shooter is doing his part.

This article first appeared in Small Arms Review SAW (March 2013)
and was posted online on February 1, 2013


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