What Effect Does Stress Relieving Have on a Barrel’s Performance?
The phrase “stress relief” is a slang term that applies to a form of heat treating. While the single-point cut-rifling process removes material from a barrel blank, other forms of rifling (including button rifling) cold-form the barrel. This cold forming process introduces stresses into the material.
While there are a variety of performance improvements as a result of the stress relieving process, the primary benefit is increased dimensional stability through reduced material distortion. If a button rifled barrel is not stress-relieved before contouring (or if residual stresses are not removed during the stress relieving process), the bore of the barrel will remain tight at the shank or chamber end of the barrel (where less material is removed) and will open up at the muzzle end of the barrel (where more material is removed).
If stresses remain in the barrel when contouring, the barrel may bow. Some residual stresses may have been introduced in the pre-production process from the mill, and some of those stresses may have taken place in the cold forming process.
Introducing ‘The Flamethrower’: Vortakt’s custom-built furnace designed for precision heat treatment. With a 400-barrel capacity and advanced temperature regulation, it ensures uniform stress relief and accelerated cooling for every piece.
Material Selection & The Impact of Stress Relief
All steels are an alloy of iron and other carefully selected alloying elements. At the atomic level, these elements are arranged in varying crystal lattice structures. Gaps between the iron atoms in these lattice structures typically capture carbon atoms during the quenching process (steel does not feature a crystalline structure when it is in its high-temperature liquid form). Vortakt has spent a considerable amount of time and research in building an effective supply chain that delivers the highest level of quality and consistency in gun barrel quality steel.
While 100% of our raw material is double stress relieved prior at the mill, the process there is somewhat crude, with a very fast heat treat, quench, and temper.
Types of Stress Relief – Cryogenic vs. Heat Treating
There are two primary means of stress relieving a barrel. Each process has its own set of pros and cons, but heat treating (thermal stress relieving) is the most common approach found throughout the barrel manufacturing community.
Cryogenic Stress Relieving
Many common barrel materials like 416R stainless steel are categorized as martensitic steel. The key characteristic of martensitic steel lies in the aforementioned crystal structure, which provides it with a high strength, hardness, and a significant amount of wear resistance. 200 and 300 series steels fall under the category of austenitic steel. Austenitic steels have their own crystalline structure, with excellent formability, corrosion resistance, and ductility.
Austenitic steels are unique in that they can undergo a transformation to become martensitic when subjected to rapid and extreme cooling (typically at temperatures of roughly -300°F over roughly 24 hours), increasing hardness and reducing ductility. The process of cryogenic stress relieving a barrel helps ensure molecular alignment, leading to additional accuracy and consistency in barrel performance compared to barrels that have not been cryo stress relieved.
While Vortakt does not commonly offer cryogenic stress relieving as a standard stress relief option, this process can be integrated as a special case solution if requested by an OEM client.
Introducing “The Flamethrower”
While many barrel manufacturers incorporate heat treat operations into their production process, Vortakt partnered with a furnace manufacturer to tailor the design to custom-build a furnace for its specific application.
This furnace (referenced internally as “The Flamethrower”) was custom-built to maximize the working envelope, effectively regulate the maximum temperature, ensure overall temperature accuracy, accelerate the speed of the cooling process, facilitate built-in loading automation, and ensure uniformity of temperature throughout the furnace.
“The Flamethrower” features a maximum capacity of up to 400 barrels that can be stress relieved simultaneously. By effectively regulating airflow, The Flamethrower can transfer heat uniformly from the top to the bottom of each piece to an incredible degree.
Why Does Vortakt STRESS RELIEVE In-House?
While many manufacturers choose to outsource stress relieving operations to local heat treating facilities, Vortakt has elected to bring 100% of all barrel production operations in-house. Insourcing stress relieving with “The Flamethrower” provides four key benefits:
1. Climate Control:
Barrel manufacturers who outsource stress relieving operations pack their barrels for shipment and transfer them via truck to an external vendor. While all of Vortakt’s manufacturing bays are temperature and humidity-controlled, barrels are often exposed to non-controlled environments during transportation and storage at the vendor’s facility. This exposure to high levels of humidity and fluctuating temperatures can very quickly lead to rust formation on untreated barrels.
2. Process Management:
By outsourcing operations, a manufacturer loses control of the process, even if they define the parameters. Once barrels exit the furnace, they almost immediately want to corrode because any oil or protection of the steel is surely burnt away in the process. Immediate rust-preventative application is needed. Any additional storage and shipping time increases the potential for surface corrosion.
3. Reduced Lead Time:
When outsourcing heat treating operations, an additional seven days are required from front to back. By bringing operations in-house, Vortakt can to expedite that process to less than a full business day (typically running the furnace overnight). These barrels can be stress relieved the very same day they’re manufactured, packed, and ready for shipment to the customer.
4. Enhanced Material Handling and Fixtures:
Not only did Vortakt custom order “The Flamethrower” from the manufacturer, but we also designed and built custom fixturing specific to rifle barrels. Heat-treating suppliers will typically use universal “baskets” to house workpieces that don’t allow for uniform airflow like a purpose-built fixture. When coupled with temperature probes placed among many of the barrels to monitor and adjust the temperature through closed-loop feedback, we are also able to ensure that each and every barrel is reaching the desired stress relief temperature.
Most legacy heat treatment systems simply rely on heating the work envelope while assuming each workpiece is reaching the desired temperature. This doesn’t effectively diagnose and solve irregularities in airflow and heat transfer. “The Flamethrower” is designed to ensure a consistent temperature throughout.
An apt comparison for this phenomenon could be your kitchen oven versus a dedicated pizza oven. Your classic home oven might be able to cook a pizza, but the crust and cheese might not bake evenly from front to back or side to side. A well-designed pizza oven is constructed to ensure consistent heat application across the full surface of the pie, ensuring a nice golden crust around the full circumference!
These fixtures don’t just ensure effective temperature regulation. The method by which Vortakt stores barrels for heat treating also delivers automation opportunities for loading and unloading hundreds of barrels simultaneously, further serving to expedite the barrel production process and lower barrel prices!
If you’re a firearm’s OEM interested in learning more about how Vortakt can help, please Contact Us.
OEM Promise
Vortakt Barrel Works provides OEM rifle and pistol barrel manufacturing services to top brands across the firearm industry. By effectively harnessing automation technology and adhering to engineering best practices, our team provides innovative partnership solutions based on your unique needs.