Difference between Hammer Forged, Button, and Cut Rifiling

Many gun lovers own multiple rifles including AR-15’s but don’t actually know how different parts are manufactured and what processes were used. To many gun lovers this is not important, but to others, it defines the difference between a good gun and a great gun. Outlined below are the three main processes used to manufacture rifle barrels. I have outlined them at a high level, but also provided links to a great site with history and images of the process and tools used.

Note: This article does not cover electrochemical machining, electric discharge machining, flow forming or broach rifling.

Hammer Forged Rifling

The process starts with a barrel blank that is 30% shorter than the end result and a hole that is 20% larger. A mandrel is inserted into the barrel. A mandrel is a carbide tube with an outline of what the barrel should look like on the inside, which includes the barrel rifling (grooves). The mandrel is placed on a long carbide rod and is placed in the hole. At that point, the blank with the mandrel in it is placed into a machine that has small carbine hammers in it. The barrel blank is slowly pushed through these hammers and rotated. The hammers strike the barrel blank very quickly and multiple times compacting the metal down onto the mandrel. The mandrel is rotated in the barrel and pushed forward as the barrel blank moves forward to create precise rifling. As the metal is hammered down on the mandrel the rifling is created and the barrel hole gets 20% smaller. As it gets smaller the excess metal is pushed out elongating the barrel to its actual size.

Check out this more detailed process flow with pictures:

http://firearmshistory.blogspot.com/2010/05/rifling-manufacturing-hammer-forged.html

Button Rifling

Rifle buttoning is a bit easier to understand. Typically what is done is a negative image of the inside of the barrel (barrel rifling) is created at the end of a carbide rod. The rod is then either pushed or pulled through a barrel blank. Two types of barrel blanks will be used in this process. The first will be a soft barrel blank so when the negative image pushes through the barrel it is not cutting the barrel, but engraving it with ridges leading to a finished barrel. The second is hard steel that cuts the grooves into the barrel leaving sharp edges. The second process requires finishing to remove the edges and smooth the barrel.

Check out this more detailed process flow with pictures:

http://firearmshistory.blogspot.com/2010/05/rifling-manufacturing-button-rifling.html

Cut Rifling

This is the oldest process out of the three outlined in this article. Cutting a barrel is also the easiest of the three processes to understand. It is just as it sounds. A long steel rod with a sharp cutter at the end is pulled through the barrel to strip out steel. It is pulled in a rifled pattern. The cutter is run over the same grove multiple times to pull out steel until the grove it complete. This process can take hours, where the two processes above only take minutes.

Check out this more detailed process flow with pictures:

http://firearmshistory.blogspot.com/2010/05/rifling-manufacturing-cut-rifling.html

TheARGuy’s Opinion

To be honest all types of rifling stress the metal and have an impact on it so I would not let it rifling process determine if you one brand or another. You will read in many of the forums that Button is better than Hammer Forged or vise verse. Personally, we are a big fan of Hammer Forged barrels, but it is all personal preference. The problem with Hammer Forged is that is mostly used in European manufactured barrels. US barrel makers typically use Buttoning. In the long run, I would not let it affect your decision to buy one barrel vs. another.