Rifling Techniques

James Smith

5/18/2015

CRJU/FCSC 497

Professor Brown

Rifling Techniques

Broach is a long tool with multiple ¬¬cutting elements on it; it may be pulled or pushed along a work piece. The broaching was invented in the 1850s and used in World War 1, as it made powerful machines. The broach tool is hardened steel rod with multiple cutting disks spaced evenly on the rod. One advantage the entire job can be done in a single pass and provide great accurate results. ¬The disadvantage of broach cutting is that it requires some skilled workers to make the broach tools. Gang-broach has multiple cutting rings. Every ring is larger than the next one; meaning it is slightly larger in diameter. The last ring is called the groove diameter of the barrel. The rod is twisted and this provide a spiral rifling groove. There are two different broaching machines the vertical and horizontal. Vertical broaching machines can be designed for push broaching, pull-down broaching, pull-up broaching, or surface broaching. Horizontal broaching machines are designed for pull broaching, surface broaching, continuous broaching, and rotary broaching. Some examples of a gun manufacturer is Pioneer Broach Company.

Button is hardened steel or something like a titanium carbide. This button rifling was development in 1940s and still used in the United States today. This type of rifling is called button because the grooves to be cut are carved in shape of a button like surface. This button type technique can be pushed or pulled into the barrel. It attached to a rifling head; which is attached to a long rod of high tensile steel. The process of button rifling is first lubricated, before the button is pulled through it. As the hard button passes through the softer steel of the barrel, it engraves the rifling on to the inside of the barrel. The whole process takes only a minute or less. The button barrel need be stress relieved; it done by heating the barrel in a furnace to about 525-550 degrees and then slowly cooling. Some advantages are the dimensions of the final product can be very accurate. The process is very fast and the machinery used to produce is very cheap. Some disadvantages the cuts can be somewhat unpredictable due to the machinery design. Another problem is that the groove may not be centered one side might have deeper grooves than the other side due to non-uniform hardness of the barrel. Some examples of a gun manufacturer is Remington Corporation.

Hammer forging is where the barrel is hammered into shape a little bit at a time. The hammer machine beat the barrel generally 1000 to 1500 per minute. The machine reduces the barrel in diameter and increases it length. The whole process is very quick and takes only 3 or 4 minutes to make a barrel rifled. Hammer Forging was invented by the Germans in 1939. After the war, this method of rifling spread grew in popularity in Europe than Button Rifling. Stress relieved is the same as that done with button rifling which prevent the barrel from splitting or deforming later. The advantages of hammer forging is the process produces an exceptional finish on the end product. The accuracy of the bore and groove dimensions is fairly high and uniformity is maintained in the end product. The disadvantages the startup costs. Each hammer forging machine can cost over a million dollars, which puts it out of reach of custom firearms makers, who are generally small shops. The second disadvantage is that this process puts stress on the barrel while manufacturing (even more stress than button rifling) which needs to be stress relieved carefully. Some materials (such as some stainless steel alloys) are harder to manufacture this way since they harden under hammering to such an extent that it becomes harder to further work them. The leading manufacturer of hammer forging machines in the world is GFM GmbH.

Hook Method or Cut Rifling one of the oldest methods of rifling; which was first invented in Nuremberg, Germany in 1520. Hook Method consists of removing steel from the inside of a barrel using a cutting tool with a hard point. The cutter box is cylindrical in shape and is made smaller than the bore of the barrel, so that it may be inserted into the barrel as well. The advantages of Hook Method is the cutter machine is not very expensive. The same hook cutter and cutter box can be used to make different barrels all of which have a different number of rifling grooves of differing depths and twists. Hook Method can use any type of steel grades with no problems whatsoever. The disadvantages of Hook Method is not really suitable for mass-production compared to some of the other newer methods of rifling. Only skilled