*AR-15 Match Loads*
Once the M-16 and later, the AR-15, were approved to compete in the Service Rifle class, it was assumed that somebody, the Army probably, would whip up some match ammo. To date, it hasn't happened. The fodder supplied at military matches is strictly issue ball, selected from better than average lots but rarely capable of the accuracy normally associated with true target loads.
The Ordnance types are experimenting with the little 5.56, trying to improve the breed, everyone involved is being unaccountably silent about it. It may be that budgetary limitations have frustrated any full-blown development program. Perhaps the problem is purely technical. Whatever the reason, anyone interested in competing with the Mousegun or its civilian counterpart is left to his own devices, for the moment, if he wants better ammunition.
A handloader wishing to put some target or varmint loads together for a bolt-action .223 has a wide variety of components to choose from. The opposite is true for those shooting one of the semi-autos. There are plenty of excellent target bullets available; any commercial .224 slug, including those designed primarily for varmint work, probably has more built in accuracy than an M-16 or AR-15 can use. The real challenge in creating a match load for one of the Colts is to find the right powder, one whose burning rate is compatible with the demands of the gun's gas system.
The latter differs radically from those of its predecessors, the M1 and M-14. There are no gas cylinders, pistons or operating rods. Instead, the expanding gas is channeled straight back to the bolt and bolt carrier from the barrel by means of a small tube. Pressure against the carrier forces it to the rear. The carrier cam imparts a rotating motion directly to the bolt, which is then drawn to the rear by the inertia of the carrier. Hence, the amount of pressure against the bolt and the length of time it's applied determine the actions cyclic rate. The higher the port pressure, the faster the action works, and vice versa. And because the link between barrel port and bolt is direct, the slightest fluctuation in port pressure results in an immediate -- and I mean immediate -- reaction from the bolt.
Exactly what the port's operating pressure is or what the allowable limits are, I haven't been able to learn but the permissible spread must be very small. That becomes obvious shortly after the M-16 entered combat in Viet Nam.
When the 16 was adopted by the Army, 5.56 ammunition was loaded with Du Pont's IMR-4475, a powder whose granules were about the same diameter as 3031 but half their length. As the situation in Southeast Asia heated up, Du Pont found itself unable to produce enough 4475 to satisfy the Army's increasing appetite. Winchester ginned up a new ball powder, WC-846, which was accepted as a substitute and sometime later, Du Pont created IMR-8208, much like 4475, which was also accepted for 5.56 ammo.
Both new powders were slightly slower burning than 4475 but managed to achieve the same muzzle velocity without exceeding allowable breech pressures. Of course, their pressure curves were farther forward than 4475's, which meant that pressures at port, and consequently bolt, were correspondingly higher. That, in turn, kicked the 16's cyclic rate up by 150 rounds or so per minute. As the bolt slammed back and forth more vigorously, feeding problems became common. So did parts breakage. In addition, the harder-to-ignite ball powder left considerably more fouling in chamber and bolt, resulting in jams and other malfunctions. In no time, the M-16's reputation soured. Eventually, a congressional inquiry was called to investigate the problem.
Both the Army and Colt were aware of the situation and had already taken steps to correct it. Teams of experts were sent to Viet Nam to see what could be done. As a result of their recommendations, a number of corrective design changes were instituted: The buffer and action spring were revamped to increase their damping effects and slow the cyclic rate; the cartridge chamber was chrome plated; a "forward assist" or bolt closing device was installed in the upper receiver and finally, a new lubricant, LSA, was issued to the troops. All because of a slightly different propellant and burning rate!
Although generally familiar with the background outlined above, it wasn't until the initial series of my own loading experiments were over that I was able to appreciate just how sensitive the Stoner-designed gas system is. As usual, I had to learn the hard way.
I don't know what powder commercial .223 rounds are loaded with but service ammo is still charged with WC-846 or IMR-8208. Neither is available as a canister powder but WC-846 can be purchased as H-335 and Ball C(2).
H-335 is surplus WC-846, salvaged from rejected lots of G.I. ammo as a rule. Reportedly, the powder is produced by several different manufacturers; also, different storage conditions causes performance to vary slightly from one batch to the next. That, as I was reminded later, is an important consideration when loading max or near-max charges in smallish cases.
Ball C(2) is WC-846 newly manufactured by Olin. Since it all comes from one source, its performance seems a bit more uniform than H-335. I've heard that some kind of flame retardant has been added to BL-C(2) but there seems to be a considerable amount of disagreement about that. Some of its ingredients must be different from H-335's though because all that I used burned much cleaner than the latter. It left much less fouling in bore and action than the Hodgdon version.
Originally, my intent was to test all the powders from 4198 through 4064. In addition, five different match bullets were going to be evaluated with each load. My assumption was, of course, that at least one of those propellants and projectiles would prove superior to the others. It didn't quite work out that way.
For openers, I decided to follow the lead of a number of military shooters who have improved their ammunition, and scores, by substituting commercial slugs for the military bullets in G.I. rounds. Bullets were pulled from 50 service cartridges. Ten of the powder charges were weighed. They ranged from 27.9 to 28.4 grains of what appeared to be WC-846 with the mean equaling 28.2 grains. Emptying all cases, the powder was reloaded with each charge individually weighed at 28.2 grains.
Ten rounds were made up for each of the following match bullets: Remington's 52-grain hollow point, Sierra's 53-grain hollow point, Sierra's 52-grain boat tail hollow point, Winchester's 53-grain hollow point and the same firm's 52-grain boat tail hollow point. The AR-15 equipped with a Lyman 10X scope was fired, single-shot, over sandbags.
Velocities, clocked on an Oehler Model 10 Chronograph 20 feet from the muzzle, ranged from a low of 3,030 fps with the Sierra 53-grain hollow point to a high of 3174 fps turned in by the Winchester 52-grain boat tail Hollow point.
At 100 yards, groups measured from 1 1/4 to 1 3/4 inches, with the majority averaging slightly less than 1 1/2 inches. Points of impact shifted slightly from one make and weight of bullet to the next but not nearly as much as anticipated. All 50 rounds could have been contained in a circle four inches in diameter.
Unexpectedly, no one make or style of bullet proved more accurate than its competitors. I assumed that was due to the limited nature of the test. Once again, I was wrong. By the time the tests were concluded, more than 1,400 rounds had been sent downrange. Never did the Colt show a preference for any particular bullet. Each of the five types tested delivered almost identical results, regardless of powder or charge.
In retrospect, I attribute that to two factors: the exceedingly high quality of the bullets themselves, and the relatively finite potential of the test rifle.
The AR-15 is hardly a match rifle. It was neither conceived nor produced with the demands of competition in mind. Consequently, its inherent ability to shoot accurately, although better than many believe, is somewhat limited.
Offhand, I'd say the average AR-15 should be capable of minute-of-angle performance when everything's right -- but that's the most which can be expected. The bullets, on the other hand, represent some of the finest, most accurate available. Any of them are capable of much less than MOA accuracy and have demonstrated that on any number of ranges and matches over the past few years. In this instance, the rifle, not the projectiles, proved to be the limiting element.
My AR-15 is a standard production model, unmodified in any respect. It was picked up and used about four years ago, although its overall appearance indicated it hadn't been fired a great deal up to that time. Since then, and before the match load development tests began, about 4,000 rounds were pumped through it. Another 1,400 or so were added during the tests. So far, after at least 5,400 rounds, there's no sign that the barrel is losing its accuracy. Colt advises the tube should be able to stand at least 8,000 rounds before any difference in grouping ability will be noted.
So much for rifle background and the G.I. loads. I needed to test handloads from scratch. One of the first decisions concerned cases: which would be best, commercial or G.I.? To any handloader, economy is always important but if it comes to a choice between performance and saving money, most will chose the former.
G.I. brass is readily available now and much less expensive than the commercial hulls. Even so, would the latter offer more uniformity, or longer life than the former? To find out, 20 Remington cases were purchased and each weighed. The scales showed a mere 1.5 grain spread between the lightest and heaviest with the average equaling 93.2 grains. A like number of once-fired cases from Lake City were also weighed. The lightest registered 89.8 grains; the heaviest, an even 92. The mean was 91.0, slightly lighter than the Remington brass.
A test load consisting of 26.0 grains of H-335 and Winchester's 52-grain hollow point boat tail was whipped up. Forty rounds were assembled, half in GI cases, the rest in Remington hulls. Eight five-round strings were fired at 100 yards. Groups ran from 1 1/4 to 1 3/4 inches. If either make of case exerted any particular influence on accuracy, it was difficult to tell. As it happened, the smallest groups were delivered by rounds featuring the G.I. cases.
In light of that and the fact that most of the .223 handloaders I know depend on service brass, I opted for it. During the tests, some of those cases were reloaded 30 times without evincing a hint of distress. After the initial trimming, stretching was minimal.
Since the G.I. primers were heavily crimped, a Wilson punch was needed to pop them out. I tried using the regular decapping pins in the Lyman sizing die but after ruining three of them, gave up.
All handloads featured CCI primers, simply because there were a couple of thousand on hand.
Once the basic selections were made, testing began in earnest. Ten rounds of each load were made up for the five target bullets. All powder charges were weighed -- a wearisome task but, in my judgment, necessary when a case with a small capacity is involved.
Initial load was 26.0 grains of H-335. Groups were unimpressive, the smallest measuring 1 1/2 inches, the largest a whopping 2 3/4 inches. At 27 grains, the holes spanned 1 1/2 inch in the biggest cluster and a couple of strings cut slightly less than an inch. Upping the charge to 27.2 grains gave most of the groups a more rounded pattern. When 27.5 grains were poured into the cases, the groups were almost unbelievable. Of the ten fired, three measured 1 1/4 inch, one cut 1 3/8 inch, four were an exact inch, another was 7/8 and the last 3/4.
Returning from the range, I examined the fired brass. The primers were flat and a bit cratered. Miking the cases near their heads revealed that they had expanded exactly like the once fired G.I. hulls, measuring between .395 and .400 inch. Apparently breech pressures weren't excessive.
To verify those results, that load would have to be fired several more times. Since my supply of H-335 was depleted, I picked up another couple of pounds and loaded up 50 more rounds with 27.5 grains.
The first three five-shot groups clustered into 1, 1 1/4 and 1 inch respectively. The following four were marred by uncalled fliers. The last three almost doubled in size. At that point, it finally dawned on me that something was amiss; the AR-15 was much harder to control on the bags. Recoil, for some reason, had increased.
A glance at the cases showed that the primers were not only flattened and cratered but creased by tool marks from the bolt face. In addition, there was a flat shiny imprint on each head, left where it had set back slightly into the ejector hole. Even though the powder charge was the same, pressures had obviously zoomed up.
And now that the warning flags were up, I noticed something else; the 15 was flipping its empties exactly 900 to the right!
I had noticed that the 15 normally tossed fired brass about six feet to the front and 450 to the right, dumping all the hulls in a neat pile. Now, inexplicably, it was ejecting them at right angles and throwing them farther away. Could that be indicative of a change in port pressure?
Charges were dropped to 27 grains, then to 26.5. Although the empties were ejected at a 450 angle once again, groups deteriorated into patterns, running from 2 1/2 to 3 1/2 inches. Worse yet, the buttstock wouldn't stay tight for more than 5 or 10 rounds. Then, midway through a string, the bolt jammed shut.
Removing the buttstock, I found that the lower receiver extension had backed off a couple of turns. That had freed the retainer, allowing it to inch upward where the flat, sharp edges of the buffer's face had partially sheared the buffer-retaining projection and stuffed what was left forward under the bolt carrier. Hence, the stoppage.
The face of the buffer bore the marks left by the back of the bolt carrier. It was evident it had taken quite a pounding. The constant jarring must have loosened the lower extension and that was why the buttstock refused to stay in place for more than a few rounds.
All the evidence -- the additional recoil, the harsh vigor of the action, the altered ejection pattern -- pointed to a marked jump in the cyclic rate -- no doubt the consequences of an increase in port pressure. In addition, the appearance of primers and case heads pointed to high breech pressures as well. Apparently, 27.5 grains of this lot of H-335 and CCI primers pushed pressures near, or above, maximum. There also seemed to be a definite correlation between the cyclic rate and the direction and distance the 15 threw its spent brass.
A new action spring, buffer and retainer put the Colt back in shape. A trip back to the range and 50 rounds of service ammo proved its former accuracy had been restored.
The entire H-335 series had to be re-fired but this time an additional step was added to the test procedures. At the beginning of each range session, 10 rounds of GI ammo were fired. A circle was drawn in the dirt, encompassing the pile of empty hulls, and a small stake was driven into the center. Since the rifle's position on the bench remained the same, ejected brass should land near the stake -- providing port pressure didn't vary from the norm too much. If port pressure influenced ejection patterns, empties landing left of the stake would indicate low pressure; those on the right, high.
At 26.5 grains, groups were running from 1 to 1 1/4 inches and the brass was landing around the stake. Two more tenths of a grain were added to the powder charge before the hulls moved appreciably to the right. There was no increase in accuracy.
The same approach was taken with BL-C(2). Combustion seemed much more complete with the Olin propellant. Both bolt and bore were much cleaner after 50 rounds than they had been when cases were charged with H-335.
The starting load with 3031 was 24.5 grains. Accuracy was excellent, with most groups measuring one-inch, center-to-center. Best performance was recorded at 25.0 grains. A number of 3/4 inch groups were fired, with the majority registering an inch and a few more expanding slightly to 1 1/4.
The empty cases were piling around the stake. Adding more powder shifted the point of impact to the right and groups opened up somewhat. AT 25.2 grains of 3031, the fired cases were some 3 to 4 inches right of the stake and groups were ranging between 1 1/4 and 1 1/2 inches.
Turning to 748, 25 grains put most bullets into groups slightly less than one inch, center-to-center. The empty cases struck about six inches left of the stake. Gradually-increased powder charges changed groups little until the 27.0-grain level was reached. At that point, some opened up to 1 1/4 inches but the majority continued to cut one-inch. As more powder was added, the empty hulls began landing to the right of the stake and by the time the charges hit 27.4 grains, groups averaged 1 1/4 inches.
Next came 4895. Starting with 25.5 grains, groups averaged 1 1/4 inches. Best accuracy was recorded between 26.0 and 26.2 grains. At the 26.0-grain mark, the empty cases were hitting the ground about four inches left of the stake; at 26.4 grains, some four inches to its right. Groups began to expand at that point. In addition, primers were flat and heavily cratered. It looked like a good place to stop.
All five of the powders tested endowed the 15 with near-MOA accuracy but some offered advantages others didn't. The surplus powders, H-335 and BL-C(2), for example, developed higher velocities than any of the canister powders. However, 335's burning rate seemed to vary too much to suit me. And it was dirtier than any of the other propellants. Of the two, BL-C(2) was by far the better choice. Its performance seemed more uniform from one batch to the next and it was much cleaner-burning, too.
An excessively fouled bore degrades the 15's grouping ability. When firing H-335, I learned to swab the barrel after every 30 rounds. With the cases filled with BL-C(2), cleaning every 50 rounds was enough to maintain accuracy. As many as 80 rounds could be sent downrange before any noticeable widening of groups could be detected when the propellants were 3031, 748 or 4895.
Winchester-Western's ball powder, 748, proved very dependable. Its velocity levels were a shade lower than those achieved by the surplus powders but it proved exceptionally clean burning, gave consistently good accuracy and uniform performance.
Although 4895's burning rate is a tad slower than 3031's, the two propellants perform remarkably alike in my rifle. They even resemble one another. In the accuracy department, however, 3031 demonstrated a slight edge. As a matter of fact, the tightest groups fired during the entire series were turned in by rounds packed with the old favorite.
The appeal of their lower price tags notwithstanding, neither of the surplus powders tested would be my choice for a match load. Their characteristics, which are shared by many propellants stored for long periods under varying conditions, vary sufficiently from one batch to the next to make performance vary slightly.
Ball C(2) is okay for practice rounds but whenever a new can is opened, it would be a good idea to make up a handful of reduced-charge check loads to see if pressure levels, both breech and port, are where they should be.
Although all the canister powders tried will do the job, 748 offers a couple of advantages its competitors don't: it measured much more uniformly than the rest and its burning rate seemed closest to WC-846's -- no small consideration with a gas system as sensitive as the AR-15's.
So far, the apparent relationship between port pressure and ejection patterns is just that -- apparent. Both evidence and logic point to their interdependence, but I can't prove it. Until someone shows me where I'm mistaken, I'll continue to believe they are and gauge fluctuations in port pressures by the ejection angle of the brass.
One final point: substituting different cases or primers for those used during the tests just described is bound to have an effect on pressures, both breech and port. So play it cool. Approach all loads from below, very gradually. And at the first hint of increased recoil or a change in the cyclic rate, back off!
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