By Mark White
Hiram Percy Maxim (1869-1936) was the offspring of the inventor of the world’s first modern machine gun, Hiram Stevens Maxim. H. P. Maxim started developing one of the world’s first modern metallic firearm silencers, shortly after the dawn of the 20th century.
The nature of supersonic (beyond the speed of sound) gas flow from a firearm’s discharge was not totally understood by scientists in the early 1900s. They did not have ultra high-speed photography available back then, and they did not understand how a flow of supersonic propellant gas would create a loud gunshot noise. Regardless of this, Maxim did understand that the sudden and violent exit of high velocity propellant gas from the muzzle of a firearm was directly responsible for the loud noise associated with gunshot discharges.
We in a more contemporary world now realize that most physical objects moving through our atmosphere at a rate of speed beyond 1,100 feet per second (fps) will create the phenomenon known to the world as sonic crack. The tip of a leather whip, when snapped rapidly, moves at a rate of speed beyond 1,100 fps, creating its own sonic crack. A bullet moving beyond 1,100 fps creates two similar sounds, one from the front and one from the rear. Surprisingly, human ears can hear both sounds and discern them, one from the other, if the mind concentrates hard enough.
In today’s world, a common U.S. military M16 rifle discharges a 62-grain bullet at a velocity close to 3,000 fps. The mass of propellant gas, being much lighter and extremely elastic, leaves the muzzle of that same firearm at roughly 16,000 fps - many times beyond the speed of sound. It is not widely known, but the energy of exiting propellant gas from a high-powered rifle constitutes roughly 90% of the force available, while the bullet represents but 10%.
A mass of exiting propellant gas forms or gathers into a hardened front resembling a curiously rounded, elongated disc - known to ballistic scientists as a Mach disc. With a .308 rifle, that Mach disc is close to 5 inches in diameter, and it actually turns into a solid state for a fleeting moment. The supersonic disc projects a very loud noise in all directions, like an extremely loud speaker. That violent impulse of sound is so loud and so powerful that it can and will cause permanent hearing damage to any unprotected individual in close proximity.
Most firearm discharges form Mach discs. With a .22 LR rimfire pistol the exiting gas (only about a grain in weight) forms a smaller, elongated Mach disc well under an inch in diameter. Even though the smaller Mach disc is very temporary (less than 6/1,000 of a second in many cases), it causes an impulse sound that is so loud that it too will also cause permanent hearing damage to those unprotected ears in close proximity.
It is extremely unlikely that Maxim knew what a Mach disc was in the early 1900s, but he soon figured out that he had to first capture and then slow exiting propellant gas from a firearm in order to silence its report. Maxim used soft, malleable iron to form gas shearing baffles of various shapes, using stamping procedures and stepped metal forming technology. A brilliant engineering graduate of The Massachusetts Institute of Technology (at age 16) Maxim experimented with different techniques and baffle designs for capturing the violent blast of gas discharge - thus confining the (still unknown) Mach disc and slowing the velocity of the remaining gases below the speed of sound in air before they exited. His vision and hard work were eventually rewarded. At the age of 40, Maxim was awarded U.S. Patent No. 916,885 for his Silent Firearm, on March 30, 1909.
Maxim’s patent and deceptively simple baffle design resulted in a silencer about 1.35 inches in diameter by a touch under 5 inches long. Because all firearms of the day used relatively low, open sights, he developed his silencer with an unusual eccentric design that didn’t occlude the view of iron sights on rifles and pistols.
The Maxim Model 1909 silencer worked extremely well on .22 rimfire rifles, since they achieved a fair (but subsonic) bullet velocity with relatively low terminal gas pressure. The .22 caliber lead bullets of the day were covered with beeswax mixed with animal fat, which tended to protect a rifle’s bore. Highly corrosive materials in the priming and propellant gas required that a Maxim silencer be removed and boiled in soapy water after each and every use. It then had to be drained, dried and re-oiled to prevent destructive corrosion. Most of the early Maxim silencers have been ruined over the years because they lacked this high level of care. Almost all ammunition in the 21st century is now loaded with non-corrosive priming compounds and propellants, which currently negates the need for extreme care. Crud will continue to build up in .22 caliber silencers, but it will at least be non-corrosive crud.
The use of the 1.35 x 4.5-inch Model 1909 Maxim silencer on .22 rimfire rifles was very successful, but there must have been problems with rotation (clocking) of the narrow part of the can so that it could be nearest the top side of the weapon to which it was fitted. A silencer gets most of its axial alignment from mating with a shoulder at the base of threads on a barrel, with rotational alignment being almost an afterthought, initially. Rotational alignment is a real problem with an eccentric silencer, however, and thread wear (or QD coupling wear) eventually causes more and more rotation to occur. Thus a can that was properly affixed when new would eventually have the thicker side of its body intruding into the sight plane as threads and seat wore with use. Maxim provided an adaptor of hardened steel, with interrupted threads. This allowed the silencer to be easily attached and removed.
A perceived need for a thinner silencer design soon led to the adoption of the 1910 Model, which was about an inch longer in the body, smaller in diameter and considerably less effective. The longer, thinner 1910 Model silencer worked fairly well on both pistols and rifles, but it is not considered as desirable as the earlier 1909 model by suppressor cognoscenti. Again, the longer 1910 Model is much louder than the shorter, fatter, eccentric 1909 Model. An open space (containing no baffles) at the rear of the 1909 Model makes it more effective on a .22-rimfire rifle, but it still performs very well on a pistol.
Both models of silencers were sold by mail order, for about $5, a considerable sum back then. They shipped directly in a sturdy cardboard mailing tube with a metal screw cap, and with a U.S. postage stamp pasted directly on said cardboard tube. While the silencers were easily obtained, they required careful threading on a gunsmith’s lathe to prevent destructive baffle strikes by bullets. Major firearm manufacturers of the day sold weapons with factory-threaded barrels to accommodate Maxim silencers. Maxim also made hardened, interrupted thread couplings with shims that could be driven onto the ends of non-threaded barrels with a mallet. These fittings sometimes lacked accuracy because most barrels were not of standard and true dimension, but they did help with the difficult problem of rotational alignment. In truth, the fitting and installation of threads or a coupling by a gunsmith probably took a lot more time than it took the Maxim factory to actually manufacture the silencer itself. Few gun barrels are truly straight and concentric, especially those built in the early 1900s.
As the silencer industry progressed, quiet shooting became widely accepted. One was considered rude if he did not silence his firearm to avoid annoying family and neighbors during target practice. Finely crafted, stained and varnished Maxim boxes were filled with sand and used as indoor target backstops, so that target practice could be held indoors on special occasions and during festivities. The two-chambered boxes contained sand in the rear chamber to stop bullets. Densely packed rags in the front chamber kept the sand from leaking out. A replaceable wood panel in front kept the rags in place, and also provided a surface for mounting a target face.
Maxim and his silencers had a pretty good run for about 25 years. In the early 1930s, during the depths of the Great Depression, the U.S. Congress suddenly took it upon itself to ban all pistols in the country. This gun-grabbing act led to citizen anger and a massive public outcry. It resulted in a widespread and massive political correction during following congressional elections. The pistol ban was struck down in federal court, and quickly reversed a couple of years later. Unfortunately, some of the guilty legislators had another few years to run before their terms were up, and in 1934 they passed the National Firearms Act, which placed a restrictive tax on machine guns, shortened long firearms and a few related items.
This sudden legislative move in 1934 proved to be a devastating blow to the Maxim Silent Firearm Company. Fortunately for the survival of the company, it had already moved into the area of silencing internal combustion engines for motor-driven vehicles. Hiram Percy Maxim died a little more than a year later, from a very sudden illness.
Very few of the original, fragile, 1909 Maxim silencers exist today, most having been destroyed through loss, mishap, ATF confiscation or corrosion. Even though the Maxim silencer technology is over 100 years old today, it is still very good technology, and surprisingly effective in our contemporary world. It is interesting to occasionally use the historic Maxim 1909 silencers and compare them with what we have available today, since they are still quite competitive when used with subsonic rimfire ammunition and moderately long barrels.
The Maxim 1909 Model Silencer and Related Notes:
According to respected silencer expert Al Paulson, all of the original Maxim papers, patent drawings and original inked drawings remained in the hands of Maxim’s New York City attorney, who died many years ago. These were put into sealed storage in cardboard boxes in an attic of a law office in NYC, and only came to light about 10 years ago. At that time they were offered for sale for a handsome sum. I have not followed up on what became of them. I believe that they still exist, somewhere, and that the collection was not broken up. There is another collection of Maxim papers residing in a State Museum in Hartford, CT.
The original Maxim 1909 .22 LR silencer was said to have been the most effective of all of those built by the Maxim Company. It is easily the equal of many of those built during the 20th and 21st centuries. According to Al Paulson, the 1909 measured 4.88 inches in overall length by 1.35 inches in diameter. The main tube is a scant 4.55 inches in length. There is a 3.77-inch long groove pressed into the bottom of the dead soft tube, as a sort of key used to hold the baffles upright. The rear thread size is typically 1/2-20, RH. It weighs 6.8 ounces. In the past I have been able to examine an original Model 1909 that was attached to what apparently was at one time a Quackenbush .22 LR rifle, turned into a pistol and used for many years in a slaughterhouse. According to Al Paulson, the unit turned in a respectable 118 dB sound level when tested with 40-grain subsonic .22 LR ammunition on a pistol. The Model 1910 tested at 126 dB.
The Maxim 1909 used flat baffles with a deceptively simple, tiny scoop stamped into the rear face of each baffle with a punch. When used in combination with the eccentric design, the tiny scoops forced incoming propellant gas into the lower section of the eccentric can between each baffle. The 1909 Model was and still is remarkably effective. The two proximal (rearmost) baffles are of a thicker material and are about 3/8-inch apart. The rest of the baffles are about 1/4-inch apart, quite thin, and they go all the way up to the front end cap.
While brilliant in design, authentic Maxim construction is fragile. Maxim silencer construction was crimped, and it was definitely not solid. The dead soft metal in the main tube or body has very low tensile strength and little resiliency. Dropping the can on a hard surface could definitely injure alignment.
I am indebted to Al Paulson for clarification of a number of conflicting issues and information relating to the Maxim Silent Firearm Company. Because of the 100-year elapsed period of time there have been more than a few facts and events that took knowledge and research to reconfirm.
This article first appeared in Small Arms Review V15N2 (November 2011) |
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