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In firearms, freebore (also free-bore, free bore, or throat) is the portion of the gun barrel between the chamber and the rifled section of the barrel bore. The freebore is located just forward of the chamber neck and is cylindrical in shape.
The International Confederation of Fullbore Rifle Associations (ICFRA) is the international association for the fullbore rifle shooting sports of target rifle ('TR') (called 'Palma' rifle in the US) and F-Class, which are long range competitions shot at distances between 300 and 900 meters or 300 to 1,000 yards depending on the range. [1]
Note: Use of this table for estimating bullet masses for historical large-bore rifles is limited, as this table assumes the use of round ball, rather than conical bullets; for example, a typical 4-bore rifle from circa 1880 used a 2,000-grain (4.57 oz; 129.60 g) bullet, or sometimes slightly heavier, rather than using a 4-ounce (110 g) round ...
The BORS mounted atop a Leupold Mark 4 M1. The computer built into the BORS, constantly updates to account for changing factors. Barrett states that the BORS "instantly takes care of the data work so the shooter can focus on the task of putting lead on target."
The bullet must tightly fit the bore to seal the high pressure of the burning gunpowder. This tight fit results in a large frictional force. The friction of the bullet in the bore does have a slight impact on the final velocity, but that is generally not much of a concern. Of greater concern is the heat that is generated due to the friction.
The name, derived from an old English practice of bore measurements in gun-making which refers to a nominally 4-gauge bore, that is, a bore diameter that would accommodate a pure lead round ball weighing 1 ⁄ 4 of a pound. This would imply a bore diameter of 1.052-inch (26.7 mm), however in practice the bore diameter varied greatly as, in ...
There are two styles of small-hole gauges: full-ball and half-ball. The full-ball gauges are easier to set correctly and maintain, under the pressure of measurement, a better representation of the bore. Half-ball gauges tend to spring just a little bit, and this may be enough to make a measurement incorrect.
Rock-quality designation (RQD) is a rough measure of the degree of jointing or fracture in a rock mass, measured as a percentage of the drill core in lengths of 10 cm or more.