A disassembled Zermatt TL3 receiver and bolt showing minimal parts for ease of changing. Simply twist out the firing pin assembly and use the firing pin to gently push out the steel pin holding the bolt head in place and remove the bolt head. (Photo courtesy of Colton Bagnoli)
October 31, 2024
By Colton Bagnoli
DIY gunsmithing is one of the best hobbies a rifleman can pick up, despite the fear many have of “messing up” a rifle. The ability to work on your own firearms at home is a great benefit to not only saving money but also having a better understanding of how your specific firearms work. This familiarity with the function gives you a steep advantage in diagnosing issues when they arise. Aside from the joys of just tinkering and trying new parts, DIY gunsmithing opens up many doors into assembling your own rifles.
Optics, stocks, actions, and barrels are expensive, so the idea of building multiple rifles to try new cartridges can be a huge hurdle for some, with rifle prices ranging from $1,000 to $10,000 for bolt-action rifles and most quality rifles averaging around $3,000. If only there was a way to have one or two rifles with the best optics that allowed you to cover any cartridge from .223 REM-.338 RUM by simply swapping out a barrel, magazine and bolt head? Enter the Pre-fit barrel, giving the DIY Gunsmith endless possibilities for a lot less money building a switch barrel rifle system.
What is a Pre-fit barrel? Pre-fit barrels offer a shooter many choices in barrel configuration, chambering and length to suit just about any application without having to build or buy a new rifle. (Photo courtesy of Colton Bagnoli) A pre-fit barrel is simply a barrel that has been threaded to a specific receiver thread pitch and bolt head, then chambered to a specific cartridge that will headspace within SAAMI specs for the given receiver design without actually having the receiver present. Modern machining allows barrel manufacturers and gunsmiths across the country to make CNC programs to mass produce the Pre-fit barrels with astonishing tolerances and headspace specifications. This allows the end user to purchase barrels for their given receiver manufacturer and swap out barrels at home with a simple barrel vise and action wrench. Making one custom rifle, turn into 2, 3, 5, or even 10 different chamber offerings by changing the barrel and, at times, a magazine or bolt head.
Bolt Face Dimensions Top to bottom shows the Magnum, Standard and .223 bolt faces for the Zermatt Arms TL3 and Origin receivers. Simple to swap bolt heads offers a cheaper alternative to buying actions with extra complete bolts to accommodate different case sizes. (Photo courtesy of Colton Bagnoli) Depending on the type of receiver you select, the bolt of the receiver is often made to a specific bolt face diameter to fit a rim diameter of the chosen cartridge. For example, many of the Magnum rifle cartridges share a bolt face diameter of .532” which is the same for 6.5 PRC, 7 Rem Mag, 300 WSM, 300 WM and 300 PRC to name a few. Standard bolt face for 30-06 based cartridges and short action cases like the .308 WIn measure .470”. Leaving the smallest cases like .223 and 300 Blackout to a .380” bolt face dimension. This requires a different bolt or bolt head depending on the cartridges you select to run. So at a minimum you would need 2-3 bolt heads to make a single action work for the majority of cartridges. However, a small case like the .223 is less than ideal for a long action receiver. Leaving you with a need for one short action and one long action receiver to best cover your options.
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Repeatable Tolerances Aero Precision, Impact, Kelbly and American Rifle Company make unique receivers to their brands while maintaining tight tolerances to allow Pre-fit barrels to be used on their products. (Photo courtesy of Colton Bagnoli) Bolt action manufacturers such as Zermatt offer interchangeable bolt heads to allow the user the option of swapping bolt heads easily without a single tool. For a dedicated switch barrel rifle, the Zermatt Origin and TL3 are my go-to receivers for my test rifles using Pre-fit barrels . One short action and one long action TL3 and 5 bolt heads allow me to make these two rifles into just about any cartridge chambering I want by simply changing the bolt head and magazine. This is by far the best system for those wanting maximum interchangeability.
For Bolt action receivers that offer Pre-fit barrels, the top manufacturers are Zermatt, Falkor, Lone Peak, Kelbly, American Rifle Company, Defiance, Impact and Terminus actions. These are all leading manufacturers of aftermarket receivers who offer repeatable tolerances to allow Pre-fit barrels without sacrificing accuracy or safety. Tikka, Savage, Ruger and CZ also make production quality actions that allow Pre-fit barrels to be used on their factory rifles but may require a new upgraded stock to accommodate the larger diameter carbon fiber-wrapped barrels mostly widely used by PROOF Research .
Pre-Fit Barrel Manufacturing Leaders PROOF Research was the first major manufacturer to put cut rifle, Pre-fit barrels on the market and still maintain the lead in quality and quantity of options for pre-fit barrels. Using state-of-the-art machining and technology, PROOF is capable of mass producing pre-fit barrels that hold tolerances rarely matched by the best gunsmith on a manual lathe, turning barrels one at a time.
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TS Customs is a custom rifle manufacturer in South Dakota that has begun offering high-quality pre-fit barrels machined on BenchMark Barrels and custom rifle barrels in both stainless steel and carbon fiber-wrapped barrels. TS Customs is known for making some of the best custom rifles on the market and now offers pre-fit barrels to give customers more barrel options for replacing match barrels or swapping out barrels on a Switch rifle system.
Preferred Barrels pre-fit barrels offer shooters a button rifled barrel for many factory rifle makers including Howa, Ruger, Savage,Tikka, Sig Cross and host of custom receiver manufacturers as well. Preferred offers many different barrel configurations in carbon wrapping and fluted stainless steel barrels to fit just about anyone's design criteria.
Tools of the Trade The tools needed for the job are pretty simple and you may have some in your tool box all ready. An action wrench, ½” torque wrench and ½” breaker bar are needed to tighten the barrel in the vise and to install or remove the action from the barrel. (Photo courtesy of Colton Bagnoli) With barrels and receivers in hand, the tools required to swap out barrels are really simple. First off, while no manufacturer will state this, you can simply hand tighten the barrels to the receiver and go shoot. For decades, some of the best benchrest shooters have shot 2-3” groups at 1,000 yards with their barrels hand tightened to the receiver. Torquing the barrel onto the receiver keeps your headspace set and keeps the barrel from backing off. Most manufacturers set a 50-75 ft/lb recommendation for the barrel and receiver, but I seldom tighten mine above 50 ft/lbs. It's plenty safe and accurate, and when I want to change barrels, I can easily loosen the barrel without spinning the barrel in the vise trying to break the 100 ft/lbs of torque. When I know I am just going to shoot it for a short period of time, say trying a new bullet or forming brass, I just hand tighten the barrel, but for a hunting rifle, I torque my barrels down to 50 ft/lbs.
The SAC (Short Action Custom) barrel vise has proven to be very effective for the job as a bench mounted vise including the aluminum bushings for each barrel diameter. (Photo courtesy of Colton Bagnoli) For barrel vises, I recommend the Short Action Customs Modular barrel vise for its ease of use . This vise uses aluminum bushings to match the contour of the barrel to get a secure fit to break the torque even when they are extremely tight. The bench top mounted vise mounts up easily and offers a ton of extra add-ons to expand the vise from barrels to ARCA plates for securing rifles, optics and other SAC accessories to your bench top for work.
Lastly, a quality action wrench to fit the inside of your intended receiver will allow you to use a long handled torque wrench and breaker bar to take your action and on and off the barrel after it is secure in the barrel vise. Many action makers offer a specific wrench for their receivers, but I also recommend the SAC modular wrench for its ease of use with Delrin bumpers. The wrench body is designed to break before causing damage to the receiver when removing and installing barrels properly. If you're taking a factory barrel off a factory rifle for the first time, it is highly recommended to have a qualified gunsmith remove the barrel for the first time, as they are often tightened to obscene levels of torque and can cause issues if not removed properly. Once the factory barrel is off, you can start torquing them to a much more reasonable standard for ease of use without sacrificing safety and accuracy.
Keep in mind, no one offers a Rem 700 Pre-fit barrel, as the spec tolerances of a factory Rem 700 vary greatly at the current time, as do many other manufacturers. When the receiver tolerances are not repeatable within a certain range, barrel makers are unable to make barrels for that receiver. Be sure to research the companies you plan to purchase rifles from if switching Pre-fit barrels is in your future to make sure they are capable of using Pre-fit barrels. Switching out barrels on rifles is a great way to maximize your tinkering with new cartridges at the range without having to buy or build a new rifle every time you want to experiment. Check out the above-mentioned companies for more information on their products and how to get started in the Pre-fit barrel game.