Just like skinning a cat, there are many ways to make a barrel. Each process is capable of producing a barrel that is great in its own right in servicing targeted market segments. In short, there are three primary processes used to make your projectile directing pipe. There is a lot to be said about each process and, as we will discuss in an upcoming post, a TON of misinformation about what each does for a rifle and requires of the shooter.
As a bit of a primer, today we will be focusing on the three most common processes used by hundreds of barrel manufacturers the world over: Button Rifling, Cold-Hammer Forging, and Traditional Cutting. (Photo Credit: Sand Hammer Forging)
Before I lay these processes out, I want to be clear on a few things. First, I am not a metallurgist. I did not spend years learning the minutia of the material properties resulting from any of production process. Second, I am not a ballistics expert or physicist. I only intend to impart a concise, surface-level understanding collected in one place to limit the necessity of a search engine. With both of those in mind, take what I say with a grain of salt. I'm not expert and do not claim to be. If you hear something different from one of the many premiere barrel manufacturers out there that contradicts what is presented here, it is safe to say that they know better because they likely have the requisite knowledge, training, and experience to claim to be an expert. With that out of the way, let's talk shop.
Like I said earlier, there are plenty of companies producing excellent barrels for the modern shooter. They can vary widely in price, application, material, and production process, but there are many reputable places you can go to find a barrel that will serve you well: FN, Daniel Defense, native Wisconsin favorites Bartlein, Krieger, and Criteron (keep 'er movin'!), and, our shop's choice, Ballistic Advantage are just a few of your options when shopping for a quality barrel. The important things to look for are quality materials, which they will brag about rather than shy away from, and strict quality control standards. As a warning to the consumer, there are many more fly-by-night operations producing inferior products that skimp on material quality or process. Oftentimes, they will be scant on production details, material properties, or product origins. As a general rule, that $75 barrel is probably not the way to go. For such a crucial component, it is worth it to pony up the extra expense to get something dependable and transparent in origin.
THE QUICK RUNDOWN(S)
BUTTON-RIFLING/GAUGING: The most common method, this is used by barrel manufacturers the world over including our supplier, Ballistic Advantage. In short, the barrels are cut from stock, bored, and reamed before having a Tungsten Carbide (or similar material) tool run through it to form the grooves in the face of the bore. This is a cold process, meaning that heat is substituted for immense pressure to push the tool through the bore as it both removes and compresses material. While burrs are produced by this cutting process, reputable manufacturers remove these imperfections with another tool that follows behind to clean the edges of the grooves. As a result of the immense pressure and compression of material, the barrels must be stress relieved to release tension from the compressed areas and prevent fissures from forming during use. This is done at nearly 1000 degrees Fahrenheit (525C) and allows the material to "spring" back. Finally, the barrel is turned to it's desired profile and threaded for the extension at the chamber end and a muzzle device at the business end. The primary benefits of this process are that it is reliable, economical, and can produce barrels that perform well when done correctly. (More info: Absolute Machine)
COLD-HAMMER FORGING (CHF): "Cold" is a relative term in this case. In this application, it means less heat than a "hot" hammer forging process. Here, a blank starts in a much chunkier state than it's final form. After being drilled and reamed, the blank is set in a hydraulic "hammer" that pounds the material into the desired shape around a die that is positioned in the bore. Unlike the other two processes, the grooves are made through sheer force compressing the barrel material rather than removing it. At the end of this stage, the compression of the material stretches the blank to the final designed length with the rifling complete. Finally, it is turned down to the appropriate profile and threaded for an extension and muzzle device. The primary benefit of this process is reduced deflection under sustained fire as a result of the higher material density. Since no material is being removed, the grains of the metal are shoved together to form the final shape rather than cut away. With this application in mind, this process is typical for military barrels that need to undergo the rigors of sustained firefights that may see hundreds of rounds sent down the pipe in short order. FN and Daniel Defense are two of the most prominent manufacturers that employ this process. More time intensive than button rifling, these barrels will usually see a dramatic increase in cost over their button-rifled counterparts. (More info: The Firearm Blog)
TRADITIONAL CUT: In some cases, the old ways are the best ways. "Cut" rifling is typically reserved for use by manufacturers geared toward extreme precision. Of the three, this is the most time-intensive and artisan-dependent process. Blanks are cut to length from steel stock before being drilled, reamed, and loaded into a hydraulic machine that cuts each groove incrementally with "hook cutters". After the desired number of grooves and, importantly, groove depth is reached, the blank is turned and threaded just like the any other. The result is a barrel that can be finely tuned to specific loads produced within precise dimensional and weight tolerances. As such, they demand a price premium for the service rendered. Bartlein and Krieger are both famed for this production process and native to Wisconsin (Keep 'er movin'!) (More info: FirearmsID)
WHICH IS BEST?
In an industry obsessed with easy answers, this unfortunately is a question that does not have one. Each process has it's own market that it is trying to satisfy. Button-rifled barrels are typically more economical and deliver great accuracy and durability for the civilian shooter when done right. CHF barrels, while more expensive, provide greater consistency under sustained fire due to the nature of the grain structure of the base material. Traditionally cut barrels are best for those seeking supreme accuracy for precision applications like long-range shooting. At the end of the day, only you can answer that question depending on your intended application. More importantly, any barrel will shoot better than you if you don't get out and train to be effective with your tool. Ammo is becoming more available and prices are steadily declining, so make sure that you budget the time and money necessary to become and/or remain proficient in your shooting. If nothing else, get out there and have some fun with a purpose!