Warrior Maven Video Analysis Above: What Will the New Marine Corp ACV Bring to Amphibious Warfare?
By Darien Cavanaugh, War Is Boring
The Soviet Union began developing underwater guns nearly 50 years ago. The idea — to arm commando frogmen and other combat divers for underwater engagements, however rare and unlikely these subsurface firefights might actually be.
In the late 1960s, Moscow enlisted “TsNIITochMash” — the Central Scientific Research Institute of Precise Mechanical Engineering, a Soviet design bureau — to work on an underwater handgun.
The thing is, water is 800 times denser than air. Even though many guns will fire underwater, making an effective underwater firearm is another matter.
“Underwater, conventional bullets are highly ineffective, being inaccurate and limited to a very short range with a rapidly decreasing lethality,” Robert Segel explained in Small Arms Defense Journal. Traditional bullets basically lose all velocity and sink or fall apart almost immediately after hitting water.
An episode of the popular T.V. show MythBusters demonstrated how even the hefty 600-grain, full-metal-jacket bullets from a high-power .50-caliber sniper rifle can’t travel more than a few feet under water before they lost their copper casing, fall apart and sink.
In a more dramatic display, Norwegian stunt-physicists Andreas Wahl placed a loaded assault rifle on a tripod underwater in a swimming pool, rigged a stringer to the trigger, stood several feet in front of the rifle and then pulled the string. The gun fired, but the bullet drifted to the bottom of the pool before getting anywhere near Wahl.
A pesky detail like physics wasn’t going to stop the Soviets.
Under the direction of a young engineer named Vladimir Simonov, TsNIITochMash explored ways of maintaining a projectile’s velocity underwater. They eventually produced a gun they believed would solve the problem — the SPP-1.
The SPP-1 looks a little different than your typical handgun. It resembles an elongated Reliant or a Derringer. The SPP-1 has four smoothbore barrels in a square cluster hinged to the frame just in front of the trigger guard. The pistol breaks open for loading and unloading.
SPP-1M on display at Tula State Museum of Weapons, Tula, Russia. Photo by Vitaly V. Kuzmin via Wikimedia Commons
The biggest difference between the SPP-1 and other handguns is not how it looks but what it shoots. The SPP-1 fires 115-millimeter steel darts with slightly flattened tips that weigh roughly 13 grams each, according to Segel. Once a dart is discharged from the gun it is kept stabilized by cavitation, a bubble-like vapor cavity created around the dart as its flattened tip moves through the water. The cavitation results in reduced drag on the dart, as well as increased accuracy and lethality.
The Soviet navy adopted the SPP-1 in 1971 for frogmen and combat divers. The gun has since been upgraded, with few modifications, to the SPP-1M and was still in use by Russian navy special forces until 2011, at least.Despite all of the research that went into the SPP-1 series, it’s still very limited. The effective range of the SPP-1M is roughly 17 meters at a depth of five meters. That range decreases precipitously as depth increases. The SPP-1M can be fired out of the water, but because it’s firing a dart through a smoothbore barrel the range and accuracy is greatly diminished in the open air. “In an emergency, at very close range, it is still highly effective,” Segel wrote about using the weapon out of water.
Not to be outdone by the Soviets, in the early 1970s the United States quickly began work on its own underwater handgun for Navy SEALs, resulting in the Mk 1 underwater revolver. It fires darts, as well — and alsolooks kind of funny.
As War Is Boring‘s own Joseph Trevithick explained in a 2014 article, a detachable six-round cylindrical magazine feeds the Mk 1. Each dart in a magazine is contained within a watertight tube that also functions as a barrel. This self-contained design greatly reduces the level of sound created by the gun discharging, both underwater and on land. To reload the gun, the operator removes the entire magazine cylinder and replaces it with a new one.
The Mk 1 has an effective range of roughly nine meters at a depth of 18 meters, according to Trevithick. The gun can also be fired in open air, but with diminished range and accuracy comparable to the SPP-1M.
Around the same time the Soviets adopted the SPP-1, they directedTsNIITochMash to start developing an underwater assault rifle. Siminov again led the design efforts, eventually developing what came to be known as the APS.
The APS underwater assault rifle has a simple design with only 42 named parts, and looks similar to the AK-47. It fires 5.66-by-120-millimeter steel darts from a 26-round magazine, according to Chris Eger writing at Guns.com. It can fire up to 600 rounds per minute, underwater or in open air. However, like the SPP and Mk 1, the APS has a smoothbore barrel. It’s highly effective underwater but nearly useless above the surface.
The Soviet navy adopted the APS around 1975. The weapon also saw service in other Warsaw Pact countries, according to Eger.
APS underwater assault rifle with single dart cartridge. Photo by Remigiusz Wilk via Wikimedia Commons
Russia’s interest in underwater firearms survived the collapse of the Soviet Union and the end of the Cold War despite the limited use of the weapons.
In 2013, Russian arms manufacturer KPB announced it had produced the first-ever amphibious assault rifle that’s effective both underwater and in an open-air environment. Operators simply have to change magazines from one holding traditional ammunition to one holding specialized ammunition when transitioning from open-air to underwater environments.
In regards to the specialized ammunition, the ADS amphibious assault rifle marks a departure from previous underwater firearms in that it fires bullets instead of darts.
“Our designers worked out a whole new way of stabilizing a bullet that’s traveling through water,” Maxim Velmezev of KPB told The Christian Science Monitor in 2013. “When it’s fired, an air bubble surrounds the bullet.”
As the Monitor pointed out, the science of the bubble created around the ADS bullets is probably based on the same technology that allows the Soviet-designed Shkval torpedo to create a bubble around itself as it moves through water. This bubble produces supercavitation and allows the Shkval to travel at impressive speeds of up to 230 miles per hour.
The gas bubble that surrounds one of the specialized ADS bullets fired underwater causes a similar type of supercavitation, protecting the bullet from the friction that usually slows down underwater projectiles. This gives the ADS a longer range and greater accuracy underwater than its predecessors.
ADS amphibious assault rifle on display in an aquarium at the 2013 Interpolitex International Homeland Security Exhibition in Moscow. Photo by Vitaly V. Kuzmin via Wikimedia Commons
The ADS weighs 4.6 kilograms, with an optional 40-millimeter grenade launcher attached. No word on how that works underwater. It uses 5.45-by-39-millimeter bullets and can fire at a of up to 800 rounds per minute with a range of 500 meters in open air.
“Developers believe that its effectiveness and accuracy are comparable if not greater than the legendary AK-47,” Russia Today claimed.
Back in 2013 KDP claimed the ADS had successfully completed tests with special units of the Russian navy and was ready to be adopted and even go on the foreign market. There have been few public announcements since then.
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