Disclaimer: This article provides no legal advice. Do NOT try this at home without familiarizing yourself with and complying with local and federal ATF laws. Otherwise, you may find yourself taking up a new residence and making new friends.
Suppressors
In my last article, Check Out the Suppressed Shotgun, I introduced suppressors – how they work, and some of the issues involved in working with them.
Suppressors are tubes mounted to the muzzle of a firearm to reduce the sound of a gunshot. The loud report of a gunshot comes from two sources. First, when a shot is fired, burning powder in the cartridge expands and propels the bullet through the rifle barrel. When the hot gasses exit the muzzle, they are supersonic, and that creates a loud report. Second, a supersonic bullet generates a sonic boom audible all along its trajectory until it slows down.
The suppressor tube contains a series of baffles. The baffles slow down the expanding gases and cool them. By the time the gases escape, the sound of the report has been reduced. Depending on the construction of the suppressor, this can be very effective, but it does not eliminate the crack of a supersonic bullet. For this reason, suppressors work best with subsonic ammunition.
Types of Suppressors
For the purpose of this article, we’ll talk about two types of suppressors. They are classified by their internal baffle construction. These are 1) Stacked Baffle Suppressors and 2) Monolithic Baffle Suppressors.
The type of suppressor selected has implications for the construction method and its performance. The monolithic baffle suppressor is simpler to construct. The stacked baffle suppressor is more complex, but has considerable advantages in terms of suppressor efficiency.
Stacked Baffle Suppressor
Figure 2 shows the construction of a stacked baffle suppressor.
Figure 3 shows a stacked baffle suppressor mounted on a pistol. Suppressors naturally become fouled with debris and residue from each discharge. A well-designed suppressor is easy to disassemble for cleaning. In this case, the stacked baffles come right out and are designed to fit together in a specific manner as they are put back in. The baffles in Figures 2 and 3 are slotted so there is no ambiguity as to their orientation. The slots also keep them from rotating around the axis. You don’t want the baffles to rotate randomly in the tube, destroying their alignment.
You can see how the baffles are constructed to fit one on top of the next. The one at the front of the device fits against the cap, which contains the crown.
Monolithic Baffle Suppressor
The monolithic baffle suppressor is constructed from a single piece of metal. It’s made from a solid cylindrical rod, usually aluminum. The rod is selected to be of the requisite diameter and fits snugly inside a sleeve that forms the outer tube. The rod is then cut to the requisite length, and a bullet path is drilled in the center, down the length of the rod.
One end of the rod is tapped where it will screw onto the threaded barrel of the weapon. The position and orientation of the baffle chambers is then marked on the surface of the rod. This is where the engineer can get creative. It seems there is an endless parade of chamber configurations. Designers experiment to see what works best.
The manufacturer then mills out the chambers. The process produces a monolithic baffle that looks like Figure 4. They then clean out the metal shavings and polish the chambers. This is part of a manufacturing process. Hand-milling requires more skilled workmen, and the number produced is commensurately smaller.
When that work is done, the baffle from Figure 4 is fitted snugly into the sleeve that forms the barrel of the completed suppressor can. The pieces should produce a nice, snug fit that forms a seal. The gases should travel from the muzzle and up through the chambers, with no leakage through the sleeve.
The finished product is a suppressor. It will look a lot like the one shown in Figure 1. That’s the shotgun suppressor from the film No Country For Old Men. The prop in the film wasn’t functional, and had to have sound effects added. This video shows how one man actually built a functional suppressor for a Remington 11-87: Anton Chigurh’s Suppressed Remington 11-87
Stacked Baffle and Monolithic Baffle Suppressors Compared
Efficiency
The key difference between the two methods is that stacked baffles can be more efficient. They have to fit perfectly and not slip out of alignment. However, stacked baffles produce more surface area to interface with the expanding gases. In that respect, they provide more cooling and slow down the gasses more for every unit length of the suppressor. Put differently, stacked baffle suppressors can provide more sound reduction per unit length than monolithic designs.
You can probably tell by comparing Figures 2 and 4. The chambers in the monolithic design have more volume, but less surface area. The stacked baffles in Figure 2 have less volume, but more surface area. As in all things, one has to balance trade-offs. Smaller volume can mean higher pressures and more noise. The sense I get is that suppressor design is as much art as science.
As you move up to hotter loads and magnum cartridges, you’re bound to want more efficient suppressors. You may lean toward stacked baffle designs.
First Round Pop
When a suppressed weapon is picked up and fired, the first shot through the suppressor can sound different compared to subsequent shots. Somewhat louder, and with a different tone. This results from the ignition of oxygen sitting in the first chamber of a monolithic baffle (called the blast chamber) or the first baffle in a stack. The effect is reduced in succeeding chambers and baffles.
High velocity ammunition, like 5.56mm, causes more first-round pop.
Suppressor designers try to minimize FRP by trying different blast chamber designs. It seems to be easier to modify the first baffle in the stack than it is to modify the blast chamber in a monolithic baffle suppressor. That’s because the monolithic blast chamber has to be milled into the desired shape. Once again, suppressor design is as much art as science.
Cleaning
This short video shows both suppressor types: Suppressor Types & Cleaning and discusses cleaning. You should be able to tell which type of construction is which. The video talks about how some designs are easier to clean than others.
The ammunition used affects the amount of cleaning required. There will always be fouling and residue blown through the baffles, but .22 ammo tends to deposit more lead. FMJ ammunition tends to blow right through and leave less debris behind.
Conclusion
My last two articles have provided a broad introduction to suppressors and some insight into how they are constructed. They’ve come a long way over the years. They used to be regarded as a tool for dirty tricks units like the OSS, spies, and Mafia hit men. Nowadays, they’ve come to be regarded as useful tools for everyone from hunters to soldiers. They provide a lot of benefits – sound suppression, reduced flash, and potentially improved accuracy. An extra pound or so added to a rifle can even mitigate recoil.
Of course, all is not roses. That extra weight has to be carried, and the suppressor does add extra length. The whole arrangement will alter the balance of the weapon and make it more awkward to manipulate. The tool also introduces an extra dimension to cleaning and maintenance.
As in all things, it will be up to the shooter to weigh the pros and cons and strike his own balance.
About the Author
You may reach Cameron at: cameron.curtis545@gmail.com
Cameron Curtis has spent thirty years in the financial markets as a trader and risk manager. He was on the trade floor when Saddam’s tanks rolled into Kuwait, when the air wars opened over Baghdad and Belgrade, and when the financial crisis swallowed the world. He’s studied military affairs and warfare all his adult life. His popular Breed series of military adventure thrillers are admired for combining deep expertise with propulsive action. The premises are realistic, the stories adrenaline-fueled and emotionally engaging.
Check out the books here: Cameron Curtis’s Amazon Page
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