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| The
Gunplumber’s Toolbox
When misaligned scope rings clamp down on a scope, obtaining a zero becomes a problem. The problem forces the shooter to crank the knobs far away from the lens' optimum center point, lowering the accuracy of the scope. Shooting a scope in a set of misaligned rings runs a great risk in damaging or even bending the scope. Daniel Solid, Engineer for Advanced Outdoors indicates, “Our products are inventions out of frustration. Using our background in machining, we decided to design and patent our own products that actually work.” The Advanced Outdoors’ SAT is a long-awaited answer to a persistent problem and will be received as an affordable unit.
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The Rockwell Scale Q: What is the Rockwell Scale (RC) and what elements are common in firearms that use steel? A: The Rockwell scale quantifies the hardness of a metal and is used by firearms and parts manufacturers when making parts. Below is the Rockwell scale and its relationship to other forms in which steel is used that you may be familiar with.
Carbon is the basic element that controls the characteristics of steel. Steel is usually made of iron and carbon combined with smaller amounts of manganese, phosphorus, silicon, and sulphur. As the content of carbon is increased, the ability that steel can be worked or stretched without fracturing decreases. Firearms often incorporate alloy steel. Alloy steel has one or more elements added to obtain characteristics like ductility or malleability necessary for a job. Common elements used in alloy steel include Nickel, Chromium, Molybdenum and Vanadium. Nickel can be added to strengthen steel and increase hardness. Chromium not only strengthens and hardens steel, it also makes steel more wear, heat and corrosion resistant. Molybdenum is often used with other elements because it improves the ability to heat-treat steel. Vanadium can be added to give steel resistance to repeated stresses.
Ballistic Coefficient Q: What is and how do you calculate the Ballistic Coefficient of a bullet? A: Simply stated, the Ballistic Coefficient of a bullet is an accurate measure of how much a bullet slows down over a given velocity and range (distance) in comparison to how much a standard bullet slows down at the same velocity and range. This ratio is the B.C. With the help of Sierra’s bulletsmiths, we are able to provide a very technical response. Ballistic Coefficient as used today in the ballistic calculations performed by commercial ammunition manufacturers is a constant that relates the bullet to the B.C. of the standard bullet (1.000) used to determine the standard drag function (G1). If the bullet’s shape caused the standard bullet to have a retarding force (drag) of “x” feet per second at a velocity of 2000 feet per second and the test bullet exhibited a drag of “2x” feet per second per second, then the test bullet would have a B.C. of 0.5 with respect to the G1 drag function. The basic formula used for years was B.C. = w/(id2) where w is the bullet weight in pounds, i is the form factor and d is the diameter of the bullet. This formula depends on a constant form factor. When this factor was conceived, it was based on the bullet’s shape and experimentally verified. With advances in test firing equipment, it has become evident that B.C. varies with velocity, hence the drag function was determined not to be constant at all velocities. Since then, it has been determined that the only way to determine B.C. is to test a number of bullets at specific velocities and combine the data. Bill McDonald and Ted Almgren have been doing these types of measurements at Sierra since 1970 using several different methods to determine B.C. Extensive discussions of their findings and a much more detailed description has been incorporated in the 5th edition Sierra manual. |
