The first thing I want to get out of the way is this: rifling your own barrel is a complicated and potentially dangerous proposition. Depending on the method you want to use, it can require extremely precise measurements, sophisticated equipment, and proper care after-the-fact to work properly.
Most often, if you do it wrong, the barrel won’t spin the bullet properly. Sometimes, however, you could create an issue that prevents the projectile from traveling all the way through the barrel, causing a catastrophic malfunction.
So, I’d advise you to use this article as a primer into the world of barrel-rifling and partner with a gunsmith for your first attempt.
How Do You Rifle a Barrel?
There are three modern methods to rifling a barrel: cut rifling, button rifling, and broach rifling. In all three methods, an object is pushed or pulled through the barrel to either cut grooves or displace metal into a spiral shape.
Rifling a barrel on your own either requires a fair bit of math and cleverness or a hefty up-front investment to purchase equipment designed for the barrel you are wanting to rifle. If you’re already fairly experienced in machining or metal-working, you may find barrel rifling much less intimidating.
Types of Barrel Rifling and How They’re Done
Cut Rifling
Cut rifling is the oldest of the three methods, and is done by cutting the grooves one pass at a time as you push through the barrel. Cut rifling is the most straightforward way to rifle a barrel, but it is also the most time-consuming and doesn’t offer much advantage over the other methods beyond being the most approachable.
The cutter is a spiral-shaped tool that is pushed through the bore of the barrel, creating a groove in the process. While this is a relatively simple and accessible way to rifle a barrel, it also requires that you have multiple cutters, or “hooks” that you can push through the barrel to get the grooves progressively deeper.
Step 1: The Bore is Made
Before you can rifle a barrel you have to have a bore to rifle. Bores are made by drilling through the middle of the barrel. This is one of the steps where absolute precision is critical. Trying to drill a hole down through the middle of a solid steel rod is tricky unless you have advanced equipment to take the human factor out of the process.
Short handgun barrels are obviously simpler than long rifle barrels, but doing it without the proper equipment can result in a bore that is not parallel with the outside of the barrel, like what happened in this video from The Idahoan Show on YouTube.
Sometimes this isn’t an issue as long as you’re fine with the barrel looking like it’s not mounted straight on the receiver, but it’s hard to be accurate when the bore points in a slightly different direction than the outside of the barrel.
Step 2: The First Pass
Once the bore is made, the rifling process begins. Typically with cut rifling, multiple passes are made to get the grooves deep enough to be effective. The first pass requires the most care when it’s done by hand, as the track that the first cut creates will be the guide for every other pass.
Since this is usually done with machinery, accuracy is ensured by the equipment, and subsequent passes simply follow along in the paths that were created by the first hook.
Step 3: Subsequent Passes
Once the first pass has been made, the cutter is then pushed through the bore again, this time with slightly more pressure. This process is repeated several times until the desired depth has been reached. One of the reasons cut rifling is not used as much in mass production is the need for multiple passes.
Step 4: Lapping
Lapping a barrel after it is rifled means to smooth out the interior of the barrel. This process helps to remove any imperfections on the surface of the barrel that have been caused by the rifling process.
Lapping is usually done using special abrasive compounds during manufacturing, but apparently it can also be done by simply coating a bullet with an abrasive and then shooting it through.
Having a lapped barrel is important – it will help to increase the accuracy of the firearm. The lapping process also helps to reduce the wear and tear on the barrel over time and prevent build-up that may eventually result in a catastrophic malfunction.
Benefits
- Mechanically very simple
- No need to destress the barrel afterwards
Drawbacks
- Not as accurate as button rifling
- Requires lapping
- Requires multiple passes and a lot more time
Button Rifling
Button rifling is a more modern method of rifling and is the most common method used today. In this method, a “button” is pushed through the bore of the barrel, creating a grooved pattern in the process. There is no cutting involved in the process, as the tolerance of the button is so perfect inside the bore that it actually pushes and deforms the steel to conform to the grooves of the button rather than slicing.
Step 1: The Bore is Made
Just like in the first method, you’ve got to have a bore to rifle before you can begin the rifling process. This is most often done by drilling. Unlike with cut rifling, though, there’s an extra step that button rifling requires before you can actually do the rifling – and that is reaming.
Step 2: The Bore is Reamed
Reaming a bore of a barrel before rifling is the process of enlarging and smoothing the inside of the barrel before adding the rifling. Bores can be reamed when the barrel is going to be cut rifled, but it’s a little more optional than when the barrel is going to be button rifled. For the button rifle to work properly, the tolerances have to be exact.
That is what reaming ensures. This process involves a reamer, which is a rotating cutting tool that is inserted into the barrel and used to slowly remove material and give the barrel a smooth finish that is exactly the right circumference for the button to push through.
Step 3: Pushing the Button Through
Once the bore has been reamed, the button is then pushed through the bore. As the button is pushed through, it creates a grooved pattern in the barrel. The way this works is quite interesting – the grooves in the button are made to create gaps, and forcing the button through slowly actually deforms the metal inside the bore to fill the gaps in the button.
Because nothing is being cut, there usually is no need to go through and lap the bore afterwards. That said, it’s no simple matter to force the button through the inside of the barrel.
As you can probably imagine, this creates a lot of pressure on the steel of the barrel, and in fact this creates so much stress on the barrel that if it’s not stress-relieved after the rifling process, it will be too brittle for use.
Step 4: Stress-Relieve the Barrel
Once the button has been pushed through the bore, the barrel is then stress-relieved. This is done by heating the barrel and then cooling it, which helps to reduce the chance of the barrel warping due to the stress of pushing the button through. The temperatures for stress relieving are around 1,100 degrees Fahrenheit.
Getting the steel up to that temperature works similarly to warming up your own muscles, actually. By heating it up, you allow the molecular structure to relax a bit and realign back to the way it was prior to the rifling process.
I’m not an expert in rifling barrels, but everything I have been able to find indicates that it’s only necessary to stress-relieve a barrel that was button-rifled, not one that was cut or broach rifled. I’m happy to be educated on the topic if any experts happen to read this article and want to leave some clarifying comments!
Benefits:
- Most accurate and perfect rifling
- Requires only one pass
- Fast enough for manufacturing
Drawbacks:
- Requires destressing of the barrel with extreme heat
- Requires high precision in all measurements
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Broach Rifling
Broach rifling is essentially cut rifling but all done in a single pass. The broach has multiple cutters in a spiral pattern that get progressively deeper as they go along. Since the grooves are cut to the proper depth in a single pass, it’s much more suited to mass production than either cut rifling or even button rifling.
Step 1: The Bore is Made
You’ve got to make the bore by drilling it.
Step 2: The One and Only Pass
Button rifling is a lot faster than cut rifling, but broach rifling is even faster, because you don’t have to stress-relieve the barrels after the rifling process. The biggest problem with broach rifling is that you don’t enjoy the same perfection in the rifling as you do when you use a button, which means you won’t ever see match-grade barrels that are broach-rifled.
In fact, broach rifling isn’t really done for rifle barrels much at all anymore, though it’s still common for handgun barrels to be broach rifled. I believe since handgun barrels are so short, their accuracy is much more affected by the short time they spend in the barrel than it is by slight imperfections in the rifling.
Step 3: Lapping
Just like with cut rifling, the barrels need to be lapped after they’re rifled. Anytime you’re cutting metal, there is going to be waste and residue left behind, and this needs to get cleared away for the barrel to function properly.
Benefits:
- Fastest rifling method
- Even simpler than cut rifling
- No need to de-stress the barrel afterwards
Drawbacks:
- Requires lapping afterwards
- Accurate enough for standard barrels, but not for match-grade
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FAQs
Yes, it is possible. The process is similar to the process described above, but the cutter or broach is mounted on the lathe instead of being pushed through by hand, which helps speed up the process and improve its accuracy. Most manufacturers use a lathe or similar for the rifling process.
Technically, yes, in some cases, a barrel can be re-rifled. This is typically done when a barrel needs to be re-chambered or when a different type of rifling is desired. It is important to note that re-rifling a barrel can reduce the accuracy of the firearm, so it is generally not recommended.
Button rifling is the most accurate, and is the method used for all match-grade barrels. The cutting process used by both cut rifling and broach rifling naturally creates some variation and imperfections in the bore, while with a button it’s physically impossible for there to be significant variations.
Conclusion
Rifling a barrel is a complex and time-consuming process, but it is essential for creating accurate and reliable firearms. There are three primary methods of rifling a barrel: cut rifling, button rifling, and broach rifling. Each of these methods has its own advantages and disadvantages, and all produce barrels with different levels of accuracy.
I would like to quickly remind everyone reading this that if you’d like to rifle your own barrel, proceed with caution, and follow tutorials from people far more experienced than me in this arena. This article is not intended as a how-to, so please do your due diligence to make sure you are going through a safe and proven process to rifle your own barrel.
