.. _Confusing Ideas & Terminology:

*****************************
Confusing Ideas & Terminology
*****************************

Zeroing
=======

When an FAC allows shooting on ranges only for zeroing, it means to allow the firing of only a few shots to make the sights reasonably accurate or to check that they are.  It does not allow shooting to improve technique and accuracy.  This makes no sense, but it is the law.


Drop Distance & Angle
=====================

Do not confuse the distance a bullet drops with the gradient of a drop per 100 yards, which you have to use to adjust the sights.  An angle, usually in MOA, may be (correctly) used instead of a gradient.


Units
=====

The practical point here is avoiding errors in unit conversion; an explanatory rant is necessary to show why the confusion arises.

The imperial unit of energy used for muzzle energy is the foot pound weight.  It is the energy required to lift a weight of 1 pound by 1 foot on the surface of the Earth (how much a pound *weighs* depends on the gravitational force where it is).  To get the energy you multiply the number of pounds you lift by the number of feet you lift them, so the abbreviation is *ft.lbwt* with the dot indicating multiplication.  Many people use the abbreviation *ft/lb*; the */* here means division, so this is not a unit of energy (you do not divide the number of feet, that you lift the pounds, by the number of pounds that you lift: lifting more needs more, not less, energy).  You may have noticed that they have also missed out the weight or *wt*, without which things can be moved more easily (such as when weightless in space).  The practical significance of this occurs if you try to convert the unit to the metric unit.  It is not sufficient to use just the conversion factors for ft -> m and lb -> kg, because the metric unit, the Joule, is the energy required to lift a weight of 1/9.80665 kg by 1m, *not* 1kg by 1m [#weight]_.


Sight Adjustment Knob Labelling
===============================

These knobs are usually labelled with an arrow and a letter, which is the 1st letter of a word that suggests the reason for turning the knob in that direction.  Some knobs have an arrow and letter for only 1 direction of turn; others have them for both.  2 types of reason are used:

#. to move the point of impact in a certain direction;
#. to correct for a certain direction of error in the point of impact.

Horizontal directions are usually described by the words *left* and *right*, and these words give no clue about which reason is being used, and so, on their own, they give no clue as to which way to turn the knob.

Vertical directions are usually described by the words *up* and *down* for the 1st type of reason, and by *high* and *low* for the 2nd; the choice here indicates how to used the other knob.

Further complications arise because foreign sights often use non-English words.  Most English sights use the 1st type of reason, most German the 2nd.  Knobs on German sights also often also have the word *bei* on their knobs.  The position is summarised as follows.

+--------+----+----+-----+------+------+-------+
|Language|    |    |     |      |Reason|Added  |
|        |    |    |     |      |      |Words  |
+--------+----+----+-----+------+------+-------+
|English |Up  |Down|Left |Right |1     |       |
+--------+----+----+-----+------+------+-------+
|German  |Hoch|Tief|Links|Rechts|2     |bei    |
+--------+----+----+-----+------+------+-------+
|Russian |    |    |     |      |      |       |
+--------+----+----+-----+------+------+-------+


Gallery
=======

* A gallery rifle is a rifle that can use only ammunition that has sufficiently little power to be usable in most pistols of the appropriate calibre.  The NRA have a more detailed definition for the guns that can be used in their gallery rifle competitions.
* A gallery range is a specific type of range, which may or may not be restricted to gallery rifles (most are not so restricted).


.. rubric:: Footnotes
	    
.. [#weight] weight = mass x acceleration due to gravity, and 9.80665m/s/s is the acceleration due to gravity.