type of special rifling that would have been impossible with the older cutting process.
Some steels give trouble in cut rifling, but can be rifled easily and better with button rifling. Stainless
steel is of this type, though it can cause trouble with button rifling through galling. There is one big
advantage in button rifling, and that is that a button reamed and rifled barrel is burnished in both lands
and grooves, and is WORKED HARDENED.
In several barrels that we ran test on we found that the steel tested out about 30 Rc before rifling and
almost 60 Rc after rifling. In addition, where the work hardening is especially great was where it is need
most, on the driving surfaces of the grooves. The reason for this fact is the maximum rearrangement of
metal takes place at the leading corners and sides of the grooves in cold swaging by the button.
Whereas the technical aspects of rifling are usually a guarded secret. We will go into some of the details
of rifling and try to make it easy to understand what has been held in secret in the past. Buttons
Specifications (burnishing) Buttons are generally made of high tensile strength tungsten, or carbide,
usually grade 883 or equivalent. These are ground to size with diamond wheels, on tool-room grinders,
or on tool post grinders. The smooth buttons used for burnishing bores, generally used before rifling,
have a leading included angle of about 3 degrees.
The flat burnishing surface is .125 in width. The trailing angle is 2 degrees, but it is not too important.
Depending on the hardness of the steel, 30 caliber buttons are usually left about .003 larger. Smaller
buttons such as 17 calibers usually are left about .002 larger. This based on the barrel steel being 30 to
32 Rc.
The bore closes in behind the button precisely predictable degree, so we can control the tolerance
within a few ten thousands of an inch.