Difference Between Cut Rifling, Button Rifling and Hammer Forged Barrels

We know that it’s hard to get parts for your 80 lower project right now. Believe us, we really know. We’re on all the gun deal subreddits, Discord servers and are always signed up for product restock alerts. But in case you’re looking for a barrel in hopes of eventually completing your 80% AR-15 build, we’re breaking down some must know facts for you before committing to a purchase.

3 Major Types of Rifling

Assuming you already know what length of barrel you want for your build, do you know what sort of rifling you want in it? These are the three main types of rifling you’ll find in barrels on the market today for your 80% AR-15:

Cut Rifling

This method is the oldest method of rifling barrels for firearms, here’s how it’s done; essentially, a single hook type cutter goes through the bore of a barrel several times to remove a little bit of metal on each pass. The process takes time and is much slower than button rifling which is why these barrels can cost more due to the production overhead.

During the cut rifling process, the rifling twist rate can be easily changed as needed and the result is a consistent twist throughout the bore with close tolerances. Perhaps its best advantage is that little to no stress is imposed on these kinds of barrels.

However, this process doesn’t work with all metal alloys which limits manufacturers to the materials they can use to make cut rifled barrels. The largest disadvantage here lies in the overlapping passes the process requires — if a mistake is made at any point it would be extremely wasteful because then a whole barrel would be easily and immediately ruined. That being said, this method is currently the most popular and widely used in the industry. While button rifled barrels can be more easily mass produced, cut rifled barrels don’t need to stress relieve the barrels.

Button Rifling

The most modern method out of the bunch — this process is the fastest, most economical and efficient compared to the rest because only a single pass is required to rifle a barrel. It’s called “button rifling” because a button is used to push or be pulled through the bore to create the desired twist rate. As the button moves through the bore it twists freely to create grooves in the surface of the metal.

Button rifled barrels are great because of their extreme accuracy from consistent bore and groove dimensions. The single pass through creates a bright and smooth finish inside the barrel which is extra nice. For high quality barrels, these must be stress-relieved or “normalized” after being rifled. If this step is skipped, the barrel would be at risk of splitting or deforming after live rounds are being fired through it. Though buttons are expensive to make, the type of barrels they produce are currently the most common type you’ll find in rifles or being sold individually on the market today.

What IS a Hammer Forged Barrel?

Typically, this is referring to cold-hammer forged (CHF) barrels which are incredibly sought after as they are among the most popular types of barrels being sold for AR style rifles. CHF barrels get their rifling from a mandrel (a rod) that has a reversed imprint of the rifling on it. The barrel is then smashed or “hammered” with the rod inside of the barrel blank which forms the rifling on the inside. When completed, the mandrel is removed from the finished barrel. CHF barrels are known for their durability, promised longevity, and high performance under rapid-fire. Which may be why it’s the only type Daniel Defense barrels are offered in. The only real downside to these barrels is if you care about weight because they can be quite heavy compared to other options on the market (but less durable).

Other Types of Rifling

The following types of rifling use similar processes as the ones aforementioned. The biggest differences here lie mostly within the form factor. See the figure below.

5R – A 5-groove rifling pattern that is sloped or angled side to the “lands.” The grooves are usually parallel in barrels while the sides of the lands are not. The 5R design takes this to the next level accentuating these factors to theoretically increase accuracy and make the barrel easier to clean.

Track 2.0 – A proprietary design exclusively made by TRIARC Systems through a process they call Single Edge Polygonal (SEP). The design combines standard and polygonal rifling shapes which aims to reduce bullet deformation, escaping gases, loss of pressure… all to allow a more symmetrical movement for a projectile or a straighter line towards the intended target.

Polygonal – A type of rifling where the traditional “grooves and lands” are replaced by softer “hills and valleys” so that the barrel’s bore ends up with a polygonal profile at the cross-section. Usually it looks like a hexagon or octagon. As an example, polygonal barrels can be found in Glock and HK handguns.