Posts Tagged ‘technology’

The Making of a Gun Designer: Charles St.George

Charles St. George at the range

Charles St. George at the range.

Bushmaster M17 bullpup

Bushmaster M17 bullpup

On the way to SHOT Show last year, I met Charles St.George. I didn’t know who he was, but somehow the Bushmaster M17 came up in conversation and turned out that he was the original designer. It was therefore no surprise that the rifle he displayed at the 2011 show looked like a very brawny M17. The Leader 50, while internally quite different from the M17 used the same basic extruded receiver design as the .223 bullpup. But the internals of the upcoming 50BMG rifle were based on a design of which I had not heard before, the Leader T2.

Charles St.George was born on Malta but moved to England with his parents at a young age. As a child, he had a Colt Peacemaker replica which even came with full-size dummy cases loaded with caps. The gun itself was precision die cast from zinc and Charles played with it until the toy literally fell apart. When his father’s regiment, the First Cheshire, got posted to Libya, Charles tried to replicate the zinc toy in steel. After a month of work with a hacksaw and a file, he had something only slightly resembling the intended form. “The experiment helped build arm muscles, at least!” he joked.

Upon returning to England, he decided to build a .303 semi auto rifle. Scotland Yard sent an Inspector from the Hampshire Constabulary to interview me at home before granting permission. Perhaps having a military father helped. The ammunition had to be kept at the Bisley Rifle Range and used cartridges logged in a register. The rifle he built used a simple tilting lock that locked the breech bolt into the receiver tube. A friend helped machine some of the parts, the rest were fashioned by hand. At the range it would not fire. In retrospect, Charles says that was lucky, for the rifle would have blown up. He knew nothing about metals, heat treatment or the designing of real guns.

As an adult, Charles immigrated to Australia started to tinker again. He built .223 semi auto rifle prototypes until he had a beautiful select-fire weapon with an aluminum receiver somewhat like the AR15 and a non reciprocating charging handle like the L1A1. Long stroke gas system used a piston pinned to a tube which housed the return spring and held to the bolt carrier by a wedge held in place by the cam track in the receiver, a triangular breech bolt and wooden handguards. The design eventually entered production around 1978 as the Leader T2. In use, this gun has particularly mild recoil, especially when compared to an AR15. Forgotten Weapons shows the T2 disassembly process on video.  They also feature photos of a pre-production sample with a wood stock made before the Zytel furniture was ready.

T2 has very mild recoil

T2 has very mild recoil.

Left-hand charging handle does not reciprocate on firing.

Left-hand charging handle does not reciprocate on firing

The Leader T2 production went smoothly because the gun was designed from the start to be extremely efficient. The receiver was based on a 16 gauge steel square tube. Dupont provided the expertise for the Zytel parts, which had not previously been used on an assault rifle. The triangular bolt design (subsequently used on the Serbu rifle, the R4 and Barrett 82A1/M107) simplified the barrel extension and the bolt broaching process. The barrel blanks from Parker Hale were rifled with a simple button rifling machine also designed by Charles. It rifled a barrel blank in about 20 seconds. While T2 resembles an AR180 superficially, it is even simpler inside. All major parts can be removed for cleaning in seconds and stay captive to simplify the take-down. It used common STANAG (M16) magazines.

T2 was shown to represenatives of Italy, Portugal and Oman. About 2000 were eventually exported to the US and a few to Africa. By the time the 1989 and 1994 bans in the US caused the cessation of the production of the T2, Charles St.George had already moved on. His next rifle is familiar to Americans as the Bushmaster M17. We will talk about that design next week.

Silencer Terms and Tech, Part 1

Hiram Percy Maxim, the son of Hiram Stevens Maxim—who invented the Maxim machine gun, is the father of the firearm silencer. An early advertisement for his Maxim Silencer Company explained that the hot propellant gases from discharging the firearm “are made to whirl around inside the Silencer,” and cannot leave the silencer until they have slowed down enough to not produce a loud noise. Although this explanation of silencer operation was first printed more than 100 years ago, it still correctly describes the function of all silencers today. Before the adoption of the National Firearms Act in 1934, Mr. Maxim sold a variety of silencer designs via the US mail, at a price range of $5.00 to $9.50, for those with deep pockets.

Original Maxim ad, click for full size image, courtesy of AAC

“But wait!” some say. “The correct term should be sound suppressor, because it is impossible to make any firearm truly silent.” Even firearms with the most advanced silencers available still make some noise when fired, so the point is well taken. However, the original inventor called his device a “silencer,” and federal and state laws universally call the device a “silencer,” so this article will refer to them as silencers.

Silencers consist of a few basic parts. The envelope is the cylindrical metal tube in which the other components are stuffed. Inside the envelope are the expansion chamber  and baffles. The expansion chamber is a relatively big empty space surrounding the muzzle, and the baffles are like coffee cups stacked on top of each other with a hole drilled through the middle of them for the bullet to pass through. This is where most of the “magic” happens within the silencer. Manufacturers competing against each other for the same exact application, will design very different baffle shapes and sizes. Finally, there is a cap at each end of the envelope, one with threads—or a quick detach adapter—to attach the silencer to the muzzle, the other with a simple hole for the bullet to exit the silencer on its way to the target.

When a bullet is fired, it leaves the muzzle of the gun and passes through the expansion chamber, where the propelling gas behind it expands from the diameter of the bore to fill the envelope. The expansion chamber takes a lot of abuse as it is the first silencer part to get hit by that hot gas. As the bullet continues to pass through the envelope, each baffle catches and diverts more and more of the gas, swirling it around, forcing it to slow down, and converting a lot of its energy into heat—which gets the silencer real hot, real quick. All of this reduces the sound made by the muzzle blast. It is possible to overwhelm a silencer by using sustained full auto fire. If the rate of fire is high enough, the gas from each successive shot stacks up inside the silencer and cannot dissipate into the baffle assembly. The sound of firing will become louder and more muzzle flash will be seen until the long full auto burst ends.

"Overwhelming" a silencer with sustained fire, image courtesy of Oleg Volk

“First round pop” is a problem for silencer manufacturers. Propellant gas from the first shot of a magazine ignites the oxygen in the air inside the silencer, creating extra noise. Follow-up shots fired quickly afterward do not have the same problem because the silencer is filled with propellant gas and air that has already been burned up. When firing stops for awhile and fresh air enters the silencer, first round pop will happen again when firing resumes. A large expansion chamber tends to contribute to a lot of first round pop, but a smaller expansion chamber decreases the overall efficiency of the silencer and can be harder on the silencer’s internal parts. Various manufacturers have different ideas about what compromise is best.

Many pistol caliber silencers are designed to be operated wet, meaning the silencer can be filled with a small amount of water before firing. Upon firing, the water vaporizes, assisting the baffles in slowing and cooling the propellant gases, and minimizing first round pop. A silencer filled with water also takes longer to get hot, since the water efficiently draws heat away from the silencer’s parts. There is no doubt that a pistol caliber silencer filled with water or gel is quieter than a dry silencer— for awhile. Some water is blasted out of the silencer by the pressure from each shot and the rest evaporates quickly from the intense heat, so the wet silencer quickly loses efficiency and subsequent shots get louder and louder. The other problem with running a silencer wet is that if the barrel is tilted up, water will run out the rear of the silencer and down the barrel of the firearm, potentially causing a barrel obstruction. If the barrel is tilted down, the water simply runs out the front of the silencer and the benefit of shooting wet is lost. Some shooters have begun to experiment with filling the silencer with a variety of oil or gel based products which stick to the guts of the silencer and won’t leak out. Silencers being used with centerfire rifle calibers should never be filled with water or gel.

More silencer terms and tech, including the Vietnam-era “hush puppy” and the Nielsen device, are found in part two, coming soon!

X-ray showing competing silencer designs