The first combat weapon associated in the gun culture’s hive mind with plastic stocks? No question, it’s the AR-15. But the AR-15 wasn’t first. Before making its AR-15 prototypes, Armalite, then of Hollywood, California, made the stocks for the AR-10 — and stocks for even earlier sporting guns.
While Armalite claims the mindshare, it wasn’t the first by any means. As early as World War II, Springfield Armory developed a phenolic plastic stock for the BAR that was used on production guns beginning some time in 1944. It also made experimental Garand stocks, and would probably have made production stocks, or farmed their production out to industry, for the millions of M1s that would have been needed for the invasion of the Japanese home islands.
But Springfield was trying to do something different from what Armalite was after. The national armory wanted another material for stocks that would be stronger at the same weight. It was not until late in the M14 project that Springfield managers realized that fiber-reinforced plastic enabled them to make stocks with equivalent strength to close-grained walnut, but at much lighter weight.
The Armalite Stock Patent
While Springfield Armory backed into the discovery that composite stocks could safe weight, Armalite didn’t take that long to arrive at the epiphany. They were always about saving weight (that was the “lite” in their name), and they always intended to do it by adapting aerospace materials to the stodgier world of firearms production. Unlike today, the aerospace industry was largely located in Southern California, and it was one of the region’s largest employers — possibly the largest. Aero engineering talent was living in every street; people familiar with the latest alloys, composites, manufacturing process, and substantiation methods were everywhere. The AR-10 would be made from an aluminum alloy forging, just like a landing gear strut or a propeller hub. And its stocks would be made from the new wonder composites: resins of urea, phenolic or melamine, sometimes reinforced with fibers, adhering to an expanded polystyrene foam core.
As early as 1951, Armalite’s George Sullivan applied for a patent showing several methods of making a gunstock with a plastic skin and plastic-foam filling. (The patent was granted in 1956). This is the method that he claimed was in most practical use at Armalite at the time:
Another method of fabrication and the presently preferred one would provide for the making of the skin in, say, two parts or halves; adhering the two parts together to form the completed skin, and finishing the gun stock by casting the plastic core material into the completed skin wherein it will expand cellularly and adhere to the skin. The two halves of the skin can be produced by using a conventional mold or die as illustrated in Figure 5, laying and clamping if desired a sheet of thermoplastic skin material over the die, heating the same with appropriate heating elements until such time as the material is softened and flexible, and then drawing the material until it conforms to the inside’ contour of the die by using suction pressure between the cavity and the sheet of material; its final shape being represented by the dashed line. The two parts thus formed may be adhered together by using standard and conventional cements, after which the completed shell is filled with the cellular plastic core as explained above. An appropriate material for the skin is a thermoplastic sheet of tough, synthetic, rubber-like plastic such as is manufactured and sold by the U. S. Rubber Company under the tradename Royalite; this material being particularly advantageous in that it softens at reasonably low temperatures, cures promptly and does not require the use of a parting material to prevent sticking to the die or mold. I have found it possible to form both halves of the skin at one time by mounting the two dies together with sheet of material for each die there between; heating the same by inserting the dies into an oven or by pumping heated air into the cavity until such time as the material is softened properly so that the same can be drawn into proper shape by means of the suction pressure. This procedure permits the foaming operation to be done immediately, thus producing substantially a completed gun stock upon removing the article from the die. The flash can be trimmed off and minor finishing techniques applied.
It sounds very space age, but the early stocks didn’t hold up all that well. This Portuguese AR-10 on a semi receiver has, unlike many, pristine metal and a shiny bore, but its original furniture has been replaced by homely replacement wooden stocks, because the original ones didn’t survive the fighting in Angola.
Sullivan went on to say that the mold (die) material could be plaster, metal or plastic, suggesting “Plaster of Paris, Kirksite, or sprayed metal and Reslyn, a phenolic casting material.” Some of these materials and trade names from the patent are no longer in use. The patent also goes into some depth about the chemical formulation of the foam base and reactant (the foam was produced at room temperature), and suggests that the skin might be equally “a polyester resin by itself or in combination with fiber additives to form a resin-impregnated fibrous material”. Early AR stocks and grips appear to be polyester resin with what appears to be cotton fibers from chopped-up matting.
The resin-skins over foam core was being used at that time by German sailplane builders, and would by the end of the sixties be adopted by an aeronautical engineer named Burt Rutan. The difference between the gun stocks produced according to the Sullivan patent, and the famous Rutan moldless foam construction process, is that Sullivan envisions defining the shape by forming the skins, and expanding the foam inside; where Rutan cut blocks of exopanded foam to shape, and then skinned them, making the process self-jigging and requiring no female mold or die. Like the Sullivan process, the Rutan process can be improved with vacuum, but it’s not necessary.
A 1960 Guns Magazine showed someone’s hands pouring resin into a stock mold, from a cup, just as is shown in #12 of Fig. 2 in the patent. (US 2753642 A, Gun stock of expanded cellular plastic material).
1951 – The Sullivan Handguard (Forearm)
Sullivan had many other patents on guns, cars and even aircraft (the twin-boom cargo plane with a central pod with a rear door was his, US Patent 2,367,538). And he also had a patent for the AR-10 handguard, specifically. This was, as we’ll see, the first of many AR handguard patents.
Sullivan’s handguard didn’t exist in a vacuum, of course. Slightly ahead of Sullivan, Springfield Arsenal’s René Studler had filed a patent for one thing people often think of as an AR innovation: a metal heat shield inside a handguard. Studler’s patent drawing showed his heat shields inside the standard US service rifle of the day, the M1 Garand (US Patent 2,674,822, Forearm and handguard protector).
The Sullivan handguard patent, filed in 1951 but not granted until 1957, is very close to the final AR-10 handguard.
The holes — 8 each above and below the barrel — are intended to allow hot air to flow out the top of the guard, letting the low pressure this produces draw ambient (and cooler, therefore) air in through the bottom holes. The patent goes into some depth about materials for the guard itself — which is meant to have epoxy (isocyanalate) skins and a core of low-density, insulating foam — and the internal aluminum heat shields.
The deep fluting here is one difference from the production AR-10 guards, but the guard’s annular shape and taper are near final. Compared to a traditional walnut forearm, this concept was a multiple win: it was lighter, more durable, did not smoke (unlike linseed-oiled wood), and insulated better. If it had a problem, it was that its annular shape required the dismounting of the entire front sight base and/or removal of the barrel from the receiver to remove and replace the guard. This problem persisted through the production life of the original AR-10.
1960 — Stoner improves the handguard
By 1960, Armalite had solved the problem of handguard removal and a new patent by Gene Stoner, filed in June of that year, shows a handguard closely resembling the one shipped on millions of M16s and M16A1s, although the drawing looks like it may have been prototyped on an AR-10.
Of course, that could have been a very early AR-15 in the illustration as well. By 1960, development of the smaller AR was underway. The narrow front sight base is why we think AR-10, but some AR-15 prototypes also had these. After all, every firearm Armalite built in this Hollywood and Costa Mesa era was essentially a toolroom prototype.
The patent (US 3,090,150, Hand Guard Construction), was assigned to Fairchild, which had bought Armalite. This patent describes the standard M16 handguard through the early 1980s and introduction of the M16A2.
The patent also made a claim that was inherent in Sullivan’s design, but not claimed by Sullivan at the time: the convective cooling produced by the upper and lower cooling holes in the handguard.
1959-60: The Artillerie Inrichtingen / Portuguese Handguard
Shortly after Stoner’s filing of the patent above, Marinus A Bakker of the Staatsbedrijf Artillerie Inrichtingen of Hembrug-Zaandam, Netherlands, filed an AR-10 handguard patent (he actually filed it in the Netherlands in September 1959, but in the USA August 1960). While the original Sullivan patent resembled the Sudanese contract AR-10s’ guards, Bakker’s is clearly the Portuguese contract handguard. His objective, according to the patent application, was much like Stoner’s: to produce a handguard that could easily be removed without having to conduct major disassembly of the rifle. Bakker further posited that air would enter the forward, metal, part of the handguard, where the barrel is hottest, and then flow back and out the rear of his handguard.
Interesting to note that Bakker’s patent drawing (US 3075314 A, Hand Guard for Rifles) shows a front sight base with no gas adjustment. The rifles AI would ship with this style handguard would have a gas adjustment to allow firing of rifle grenades with blanks. (It would be interesting to conduct some firing tests with a smoke generator, as used in wind tunnels, to study the convective airflow of different handguard designs).
There were more handguard patents, and more evolution still to come, but we’re now up to date with the AR-10 and the AR-15 through the life cycle of the M16A1.
The story of Armalite stock and handguard design is a story of talented engineers pushing the limits of technology and starting with a clean sheet, first-principles review of an area of gun design that had done things “the way we always have done it” for, literally, centuries. This was consequential engineering: when the first Project Agile contract dropped, the AR-15, future M16, was the only service rifle in the world with synthetic furniture. But in the 21st Century, every military rifle in the world owes at least a little something to these venerable, and now, expired, patents you see here. Russia, with its endless Siberian expanses of birch forest, and stolid peasant conservatism, at least with respect to weapons design, held out longest of major arms makers.
Returning to the inventor we began with, George C. Sullivan had at least three more patents of interest, but not to the production AR-10 or AR-15: one was for the stock of the AR05 survival rifle (very similar to that of the AR-7, a lasting success), one for the folding buttstock of the AR-16/-18, and the last, for somewhat less of a success: an aluminum gun barrel. But that’s another story.