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Revisiting the SPIW: Part 1

By R. Blake Stevens

A popular topic for discussion among collectors is “my favorite firearm” where arms of every type and period are put forth and loyally defended. Every time I consider my own response to this fascinating question my thoughts immediately return to the SPIW (Special Purpose Individual Weapon), which was the subject of a Top Secret development program undertaken by U.S. Army Ordnance during the 1960s and 1970s, initially as an offshoot of Project SALVO (1952 - 1960).

What Was the SPIW?

SPIW was to be a hand-held weapon holding sixty rounds of “point target” ammunition (deliverable in the form of controlled bursts of tiny, lethal darts or “flechettes”), plus three 40mm “area target” grenades in a piggyback launcher, all in a package weighing less than a loaded .30 caliber M1 rifle.

SPIW promised dramatic increases over the performance of the Army’s existing small arms, both in point-target hit and kill probability, plus devastating area-fire potential. Irresistibly, these fantastic advances in combat lethality touched a responsive chord in everyone.

In actual manufacture, however, the enthusiastic all-things-to-all-people SPIW specifications translated into extreme weapon complexity and high multiple-ammunition capacity within ultra-light weight. These characteristics were soon found to be mutually exclusive, yet were stubbornly insisted upon by the Army. Unfortunately, the SPIW never materialized as an actual, combat-ready weapons system, and the program was eventually abandoned as a very expensive and embarrassing flop.

A Fatal Blurring of the Line Between Fact and Fantasy

As the program progressed into the ‘Sixties despite its deep-rooted problems, there was an increasingly political need for SPIW to figure meaningfully against other weapons, such as the M14 and M16. In order that the SPIW might participate, in theory at least, against its vastly more fully-developed conventional rivals, first- and second-generation SPIW performance at its best was projected and extended, using computer models of actual combat scenarios. The results of these biased studies, which pitted the SPIW’s theoretical best against actual simulated-combat data from competing conventional weapons, showed the SPIW as being clearly superior to the best existing weapons in the world. The heavily slanted nature of these comparative standings led to the fatal temptation to confuse potentiality with reality.

Ed Ezell to the Rescue

While attending the U.S. Army Show in Washington in 1984, I remember mentioning my fascination with the SPIW to Dan Musgrave, a very knowledgeable and respected author with a prestigious military career behind him. Dan shook his head and remarked, “You will never find out anything about the SPIW. It was so embarrassing it has all been buried so deeply it will never be found.” However, thanks to the efforts of the late Edward C. Ezell, Ph.D., then the Curator of Military History at the Smithsonian’s Museum of American History, the story was indeed unearthed in voluminous detail, and became the subject of the Collector Grade title The SPIW - The Deadliest Weapon that Never Was, which was co-authored by myself and Dr. Ezell and published in 1985. The following copyrighted material is largely excerpted directly from this long-out-of-print book.

Origins of the SPIW Program

As described in Chapter One of The SPIW, the origins of the program go back to the early postwar period, during the dawn of the computer age.

The Hall Study

The Ballistic Research Laboratories (BRL) had been formed at Aberdeen Proving Ground in 1938, with an ongoing mandate to conduct basic ballistic research for the Army. The official reason behind the ground-breaking BRL study into combat rifle effectiveness was to address the unsettling fact that, despite the Army’s doctrinal insistence on accurate, long-range aimed rifle fire, an estimated 50,000 rounds of ammunition had been expended per enemy casualty during World War II. The results of the study by Mr. Donald L. Hall were released in BRL Memorandum Report No. 593, dated March 1952, entitled An Effectiveness Study of the Infantry Rifle.

The Hall Study was the first real, authenticating publicity for the fledgling small caliber, high velocity (SCHV) concept, a new and cooperative research effort involving Aberdeen’s Development and Proof Services (D&PS) and the Ballistic Research Laboratory (BRL). Mr. Hall blended the initial SCHV results with his own theoretical studies to produce history’s first serious espousal of the small caliber concept:

The theoretical consideration of a family of rifles indicates that smaller caliber rifles than the .30 have a greater single-shot kill probability than the cal. .30 M1. This is obtained by increasing the muzzle velocity and thereby obtaining a flatter trajectory, so that the adverse effect of range estimation errors is reduced.

When the combined weight of gun and ammunition is held constant at fifteen pounds, the overall expected number of kills for the cal. .21 rifle is approximately 21/2 times that of the present standard cal. .30 rifle. If the number of rounds is fixed at 96, the total load carried by a soldier with a cal. .21 rifle and ammunition with 6/10 the charge in the M2 cartridge will be 3.6 lbs. less than that carried by a soldier with a cal. .30 rifle. This is a 25% reduction in load.

Furthermore, if it were necessary for a soldier with the M1 to carry the rounds required for the same expected number of kills at 500 yards as a soldier with 15 lbs. of cal. .21 6/10 charge rifle and ammunition, it would be necessary for him to carry 10 lbs. more ammunition, or a total load of 25 lbs.

The Hitchman Report

In September, 1948 the Army General Staff created the civilian Operations Research Office (ORO), whose initial mandate was to supply the Army with scientific advice about the conduct of nuclear war.

The second important study under discussion here complemented but greatly expanded on the Hall Study. It was presented by the head of ORO’s Infantry Division, Norman A. Hitchman, on June 19, 1952. Originally classified SECRET, ORO’s Technical Memorandum ORO-T-160 was entitled Operational Requirements for an Infantry Hand Weapon.

The Hitchman Report began where the Hall Study had left off, taking as its gospel that “it is desirable to increase in both number and rate the hits which may be inflicted on the enemy by aimed small arms in the hands of the infantry.” ORO summed up these opening remarks by stressing that the “severity of weapons as measured by their lethality has not changed, at least in the past century.”

There was stubborn Army opposition, especially among Ordnance officials, to this ORO attempt to quantify certain parameters as they truly existed, as opposed to how they had traditionally been perceived, regarding the infantry rifle and its effectiveness in combat.

Out of all the combined British and American research available, 80% of the effective rifle and LMG fire had been reported at ranges under 200 yards, with a full 90% under 300 yards. This substantiated the Hall Study, wherein hit probability from small arms fire at ranges exceeding 300 yards rapidly descended into the “negligible.”

Origins of Project SALVO

The Hitchman report’s suggested solution to low combat effectiveness was to compensate intentionally for the soldier’s inherent aiming errors by developing a new type of automatic arm capable of projecting missiles either in a burst or salvo:

...either a simultaneous [salvo], or a high cyclic rate burst, with the number of rounds per burst automatically set rather than dependent upon trigger release. In the (salvo), the scatter would be obtained and controlled by multiple barrels, a mother-daughter type of projectile, or projection of missiles in the manner of a shotgun.

The State of Affairs in the “Lightweight” Rifle Program

Consider the unfortunate state of affairs as they then existed in Col. Studler’s vaunted “lightweight” rifle program, wherein his original favorite, the T25, had evolved briefly into the T47 only to be ignominiously terminated in favor of what was basically nothing more than a “product-improved” M1 Garand. This arm, the selective-fire, 20-shot T44, had been in its initial stages of development at Springfield Armory when the Hall Study and the Hitchman Report were released in 1952. The controversial ORO/BRL results stood in direct opposition to nearly every single feature the Army had approved in the T44.

Nevertheless, the luckless M14 rifle, the final embodiment of the T44, was to be adamantly adopted as the standard U.S. service rifle in May, 1957 after five more years of snail’s-paced refinement. During this time the privately-developed .223-caliber ArmaLite AR-15 had appeared; a direct result of ORO/BRL research and the resulting SALVO studies. Ultimately, it was to render both the M14 and the 7.62mm NATO cartridge obsolete.

The Three Branches of Project SALVO

Meanwhile, the multi-agency SALVO project was initiated in November, 1952, and immediately diverged into the three main areas of experimentation already introduced above.

The Multiple-Bullet, Single-Barrel Concept

ORO became a strong proponent of the nested multiple-bullet, single-barrel salvo weapon concept, testing Duplex and Triplex loadings in a number of experimental cartridges, all based on the standard .30 caliber case.

A version of the ORO Duplex loading of the 7.62mm NATO cartridge was subsequently adopted - ORO later termed the green-tipped M198 Duplex round, with considerable justification, a “low-cost, low-risk, high-payoff innovation.” Curiously, the M198 cartridge was never made in significant numbers, nor was it ever issued in any but token quantities.

Two- and Three-Barrel SALVO Weapons

Springfield Armory and Olin (Winchester) drew up plans for several complex and unwieldy prototypes of two- and three-barreled salvo weapons, designed to fire near-simultaneous bursts of small caliber projectiles. Valuable research into the nature of burst fire was gleaned from each of these studies, but as a design for a combat shoulder rifle, the sheer and dismaying forward imbalance of their weighty multiple barrels proved utterly impracticable.

The AAI 32-Flechette Shotshell

On another tack, the Office of Naval Research had initiated a contract in 1952 with Aircraft Armaments, Inc., of Cockeysville, Maryland, to supply for test a quantity of 12-gauge shotgun shells, each loaded with 32 small nested steel “flechettes,” or arrows. Impressive preliminary tests showed that these tiny, 8-grain flechettes were capable of penetrating nearly six inches of wood at 100 yards.

Results of the Project SALVO Field Experiments

1956 was an eventful year for U.S. Army Ordnance developments. The ArmaLite AR-10 rifle had been introduced to the Infantry Board and other officers, and many thought it an admirable attempt to create a truly modern and controllable light rifle firing the 7.62mm NATO cartridge. The latest developmental model of the T44, the nine-pound T44E4, was meanwhile still nearly a full year away from adoption as the M14.

This then was the backdrop for what became known as the “SALVO I Field Experiment.” Within this framework of innovative combat simulation, three different SALVO concepts were tested during June and July of 1956, alongside the M1 rifle firing the standard M2 AP cartridge as control.

General conclusions made after the trial were that typical combat aiming errors were in fact even greater than had previously been allowed for. Automatic fire was again proven inferior to aimed single shots on point-fire targets.

The results were somewhat disappointing for Aberdeen’s SCHV concept, as the .22 test barrels tended to “walk” badly when heated by rapid burst fire, rendering the weapons extremely inaccurate and thus denying BRL’s high theoretical hit probability forecasts any conclusive, practical proof.

Regarding ORO’s “long-necked” Duplex and Triplex .30 M2 loadings, the results were extremely encouraging and substantiated the Hitchman Report’s findings that bullets fired in a simultaneous salvo are independently potentially lethal, and therefore for each shot fired a sum of lethal probabilities existed, which increased the statistical kill probability dramatically over that of single-bullet firings.

Meanwhile, the shotgun-launched clusters of flechettes were found to have a distinctive value in the short-range area-fire role, especially in darkness. In a dispersion trial, however, only fifty-two percent impacted into a 30-inch circle at 40 yards. Nevertheless, even when launched in a cluster from the relatively low-pressure shotshell, the .087-inch diameter flechettes would often pass cleanly through one side of an M1 helmet and liner at 300 yards, and would sometimes even make a hole in both at 500 yards.

The Evolution of the Serial Flechette

To the SALVO teams, there was now no question as to the effectiveness of multiple projectiles being delivered with each trigger pull. As noted, ORO had devised the Duplex bullet in the 7.62mm NATO case as the most expedient method of adopting this controlled dispersion theory. Soon, however, ORO switched allegiance to even more exciting and dramatic advances in hit probability, by marrying BRL’s concept of high velocity and consequent flat trajectory to the almost imperceptibly low recoil impulse of a lightweight, single flechette. ORO recommended that by following this path, a controlled-dispersion burst weapon could become a reality for every American combat soldier. This new weapon would be devastatingly lethal, regardless of his individual marksmanship abilities.

Sabot Refinements - from “Pusher” to “Puller”

Irwin R. Barr, one of the seven founders in 1950 of Aircraft Armaments, Inc. (AAI), was by all accounts the “father” and leading proponent of the flechette concept. He had already seen his ideas become reality in the U.S. Naval Research contract for the 32-flechette shotshell, but felt that the concept had even more to offer:

...The large dispersion of these [shotshell] projectiles and the resulting short range limitations… caused us to feel that another radically opposite approach was required to achieve the high ‘Salvo’ hit capability of a rifle at long ranges by using a short burst of serial-fired flechettes.

For several years AAI experimented with the single flechette idea without any outside assistance or funding, gambling on the eventual recognition of the flechette’s innate advantages of minimal recoil, high penetrating power, and light weight.

Two initial considerations when firing single flechettes were to guide the reduced diameter of the body of the arrow-like flechette on its short and speedy trip to the muzzle, and also to provide an adequate gas seal around it. Enter the sabot: a sort of segmented, bore-sized plug which would either sit behind the flechette and push it, or grip the body of the flechette firmly and pull it down the bore:

...All previous work by AAI on single projectiles utilized a pusher type of sabot. However, this configuration would make a cartridge too long to be satisfactory, as the propellant had to be packed behind the long, thin, needle projectile and sabot.

...The basic [AAI] idea… required a new concept. The projectile must be pulled by the sabot, which would surround the forward part of the projectile… using the gas that propels the round to push inward on the sabot of constrictable material and so generating a friction force to transmit the pull of the sabot to the projectile...

The AAI “.22 Arrow” Cartridge, with Piston Primer

Aircraft Armaments, Inc. responded to two further Ordnance R&D contracts in 1959 with a finalized first version of its “.22 caliber, Single Flechette Ammunition.” An interesting and integral feature of the slim, belted cartridge case was its unique piston primer.

In assembly, the piston primer was inserted down through the neck of the case and held securely against forward movement by means of a crimp, which showed as four distinctive dimples in the outside circumference of the case. It was intentionally positioned slightly forward inside the primer pocket, and was designed to be fired by a blow from the weapon’s flat-faced firing pin. This would collapse the whole piston forward, whereupon the internal, frontal point of the piston itself detonated the priming compound, thus igniting the powder charge. The resulting pressure inside the case not only pushed the saboted flechette down the bore, but at a certain point forced the collapsed piston backward a short distance, cushioned by the flat-faced firing pin. When the piston protruded about two millimeters (0.80”) beyond the base of the case, primer movement was halted by the flared front section of the primer body contacting the inner base of the cartridge case. The heavy-bodied firing pin continued to the rear, transmitting the energy needed through a camming action to rotate and unlock the bolt and thus begin the action cycle of the weapon.

The .22 Versus the .30 Caliber Debate: Testing Three .22 Rifles

All of this of course did not go on in a vacuum; indeed the events which by this time surrounded our story were so remarkably fraught with acrimony that probably even without the flechette program’s strictly “SECRET” classification, it would have generated little interest. By the beginning of 1959, the .22 versus the .30 caliber debate had reached a positively feverish pitch. Both the Army Infantry Board and Aberdeen’s Development & Proof Services (D&PS) had the year before held comparative trials of three contending small caliber rifles: the .223 cal. ArmaLite AR-15; Winchester’s short-lived M1 Carbine-like “Light Weight Military Rifle” in caliber .224; and an even shorter-lived Springfield light rifle design, chambered for another similarly named but non-interchangeable .224 cartridge.

The Infantry Board Favors the AR-15

The Infantry Board was initially quite enthusiastic about the AR-15, recommending in its September, 1958 report that a few deficiencies be corrected and that the modified AR-15 be summarily adopted as their ideal follow-on to the aging M1 Garand. Aberdeen, an Ordnance Corps agency, demurred. There, the small calibers were deemed inferior to the 7.62mm with regard to penetration and brush-bucking, while the AR-15’s high line of sight was seen as objectionable in that it exposed too much of the firer’s position.

These developments themselves took place in waters already muddied by the Ordnance Corps’ beleaguered M14 procurement program, which by this time was under way at Springfield Armory with an initial order for over fifteen thousand rifles.

Vetoing Further Purchases of the AR-15

In February, 1959, the Chief of Staff of the Army, General Maxwell Taylor, vetoed any further purchases of the AR-15 in favor of continued procurement of the 7.62 NATO-caliber M14. By February 17th, the first civilian M14 procurement contract was in place at the Olin Mathieson Chemical Corporation’s Winchester-Western Division, where 35,000 M14 rifles were to be fabricated at $69.75 apiece.

Colt’s Takes Over the ArmaLite AR-15

As stated in The Black Rifle, another Collector Grade title co-authored by myself and Dr. Ezell,

...An initial, 20-year “letter of understanding” was put on paper as early as September 22, 1958 regarding “the ArmaLite matter,” but it was some months before any actual money could be put together.

...Ironically, the final signing of the arrangement between Colt’s new directors and the newly-formed Fairchild-Stratos Corporation coincided almost to the day with General Taylor’s formal veto of further .22 caliber rifle purchases by the Army.

The All-Purpose Hand-Held Weapon (APHHW)

Returning to the text of The SPIW, one other Ordnance recommendation had been enthusiastically endorsed by General Taylor, which paved the way for the development of a completely new light, flat-shooting weapon that would truly qualify as the successor to the M14. It would fire patterned bursts of the ten-grain flechettes developed by Aircraft Armaments, Inc., and would be called the All-Purpose Hand-Held Weapon (APHHW).

The Infantry Board Tests the “Cartridge, .22 Caliber, Arrow”

With the M14 finally locked securely into a production program and the ArmaLite proponents temporarily stunned into disarray by General Taylor’s adamant veto of the AR-15, the spotlight slowly swung onto the flechette cartridge and the concept of the All-Purpose Hand-Held Weapon.

With the future at stake, the AAI engineers held their breath as lots of the single flechette cartridge they now dubbed the “AAI Arrow” were examined and fired in a crucial 1960 Army Infantry Board trial. The Infantry Board trial report, dated March 18, 1960, contained a list of perceived deficiencies of the flechette cartridge, which included the following:

Nevertheless, the report’s overall conclusions were very encouraging. The United States Army Infantry Board concludes that:

The “Cartridge, 5.6mm, XM110” in Arctic Trials

By May, 1960, the first-generation AAI flechette cartridge’s short-lived proprietary designation had been superseded: the “Arrow” was now officially the “Cartridge, 5.6mm, XM110.”

Results of trials of several cartridges under Arctic conditions, including 1,000 rounds of the newly-named XM110 single-flechette round along with several lots of 7.62mm M59 and M80 ball and the Winchester .224, appeared in a report prepared by the Arctic Test Board, dated May 7, 1960.

Again, the single-round accuracy of the XM110 flechette cartridge was criticized, even though the stated purpose of the APHHW program was to provide the combat soldier with the means to fire controlled bursts, intentionally spread around the point of aim. A perfected weapon capable of firing bursts of flechettes did not yet exist, however, and so there was little the Army could do except continue to record the results of single-round firings, which were often inexplicably erratic.

However, the overall consensus was again favorable with the Army being particularly excited about the XM110 flechette cartridge. Two salient paragraphs from the Accuracy Test Results section of the Fort Greely report read as follows:

...Due to the flat trajectory of the single flechette, it was unnecessary to make elevation adjustments on the sight when firing at 300 and 500 yards.

...Three rounds of single flechette were fired into eight inches of solid ice at 500 yards range. All flechettes perforated the target.

Overall, the promised APHHW was deemed definitely worthy of further development.

Competition for AAI

A parallel Defense Department flechette weapon-and-ammunition development program was set up, under which Springfield Armory was tasked to come up with an alternative proposal for a flechette-firing weapon, and Frankford Arsenal was ordered to develop the best possible competitor to the piston-primed XM110 cartridge.

One important area of commonality was stipulated from the outset: AAI’s flechettes and rubber-obdurated, fiberglass “puller” sabots were deemed satisfactory, and were to be loaded as an AAI-supplied “package” into both the XM110 cartridge and the new Frankford/Springfield round.

Thus there soon existed a new, shorter, conventionally-primed version of the single flechette cartridge, called the XM144. Design studies for two types of flechette-firing shoulder rifles were begun at Springfield.

Note: There is a significant amount of documentation, manuals, reports and photos regarding the SPIW program on website.


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