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Range
The distance between the shooter and the target. Also short for shooting range.
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Rangefinder
Device for determining range, or for optically measuring ( or estimating ) the direct distance to a target.
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Ranging
The technique that a shooter uses to compensate for pellet trajectory by using adjustable/ranging telescope.
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Rate Of Twist
In a barrel, the length over which the rifling grooves make one complete twist ( i.e. the length of the bore used to turn the pellet one full revolution ) e.g. 1:10 or one revolution in 10 inches. Differs from calibre to calibre. Pellet weight must be appropriate to the rate of twist or pellet will not stabilise in flight. The heavier the pellet, thus the longer, the faster the twist rate must be.
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Recoil
The rearward thrust of a some rifles caused by the propulsion of a projectile in the opposite direction. Refer Newton’s 3rd Law of Physics: for every action there is an equal but opposite reaction. Commonly called “kick”. The amount of recoil felt by the shooter depends on factors such as the weight of the rifle ( which absorbs some of the recoil ), the design of the stock, the shooting position, etc. Incidentally complete analysis based on conservation of momentum would have to include the angular momentum the pellet acquires, which depends on the twist rate and length of the barrel.
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Remaining Energy
A projectile's energy in foot pounds at a given range.
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Reticle / Reticule
In telescopic sights, the element which is optically referred to the target. It may consist of straight or tapered cross-hairs (wires in the tube forming a central cross ), dots, or other marks used to determine the point-of-aim, size of, or range to the target. It is also markings in a microscope eyepiece used to establish location or scale. Commonly used to measure rifling.
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Rifle Cant
Any leaning of the rifle to the left or right from a vertical position during firing. This should be eliminated because of the potential for increasing misses at longer ranges.
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Rifling
Spiral grooves in the bore of a barrel to impart a rotary motion ( spin ) to the pellet to provide it with rotational stability. This will ensure that the pellet flies true with a point-first attitude.. Methods of manufacturing are Button rifling, Cut rifling and Hammer forging.
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