Chapter XV: Part VII: Windage

1. What is meant by _windage_?

The difference between the diameter of the projectile and that of the bore.

2. Is it absolutely necessary to allow windage?

Yes, in order to make an allowance for a piece becoming foul, the expansion of shot by heat, the incrustation of rust, and for the tin straps of fixed ammunition.

3. What advantages are derived from reducing the windage?

An increase in the accuracy of fire; a more extensive range, or an equal range with a smaller charge, as there is less loss of gas; and less injury to the surface of the bore.

4. Why should the bore suffer less injury by a diminution of the windage?

Because in proportion to the decrease of windage there will be less space for the reflections of the shot along the bore, and consequently less injurious power exercised upon it.

5. What is the loss of velocity by a given windage proportional to?

It is directly as the windage, and inversely as the diameter of the bore very nearly.

[Sidenote: 81]]

6. What is the loss of velocity by the windage of the ball?

====================================================================
|Charge|Initial velocity of ball.|Loss of velocity
KIND OF GUN. | of +---------+---------------+ by windage of
|powder| Without | With windage | 1-40th diam.
| | windage.|of 1-40th diam.|
------------------+------+---------+---------------+-----+----------
| lbs. | feet | feet. |feet.| per cent.
32-pdr. Sea-Coast,| 4 | 1444 | 1271 | 173 | 12
------------------+------+---------+---------------+-----+----------
24-pdr. Siege, | 4 | 1600 | 1433 | 167 | 10
| 6 | 1890 | 1723 | 167 | 9
----------------- +------+---------+---------------+-----+----------
| 2 | 1617 | 1444 | 173 | 11
12-pdr. | 3 | 1915 | 1742 | 173 | 9
25 calibres, | 4 | 2124 | 1951 | 173 | 8
------------------+------+---------+---------------+-----+----------
| 2 | 1528 | 1370 | 158 | 10
12-pdr. Field, | 3 | 1793 | 1635 | 158 | 9
16 calibres, | 4 | 1992 | 1834 | 158 | 8
------------------+------+---------+---------------+-----+----------
6 pdr. Field, | 1.5| 1734 | 1560 | 174 | 10
------------------+------+---------+---------------+-----+----------

7. What windage is allowed to guns?

==============================================================
IRON. | BRASS.
-----------------------+-------------------+------------------
Sea-Coast. |Siege and Garrison.| Field.
-------+-------+-------+---------+---------+---------+--------
42 | 32 | 24 | 18 | 12 | 12 | 6
-------+-------+-------+---------+---------+---------+--------
inches.|inches.|inches.| inches. | inches. | inches. | inches.
0.16 | 0.15 | 0.14 | 0.13 | 0.10 | 0.10 | 0.09
-------+-------+-------+---------+---------+---------+--------

[Sidenote: 82]]

8. What windage is allowed to columbiads and howitzers?

=============================================================
COLUMBIADS.| HOWITZERS.
-----------+----------------------+---------------------------
| Iron. | Brass.
Iron. +----------+-----------+-------------+-------------
|Sea-Coast.| Siege and | Field. | Mountain.
| | Garrison. | |
-----+-----+-----+----+----+------+------+------+------+------
10-in|8-in |10-in|8-in|8-in|24-pdr|32-pdr|24-pdr|12-pdr|12-pdr
-----+-----+-----+----+----+------+------+------+------+------
in. | in. | in. | in.|in. | in. | in. | in. | in. | in.
0.12|0.12 | 0.12|0.13|0.13| 0.14 | 0.15 | 0.14 | 0.10 | 0.10
-----+-----+-----+----+----+------+------+------+------+------

9. What amount of windage is allowed to mortars?

===========================================================
IRON. | BRASS. | IRON.
---------------+---------------+-------+-------+-----------
Heavy. | Light. | Stone |Coehorn|Eprouvette.
| |Mortar.|24-pdr.|
-------+-------+-------+-------+-------+-------+-----------
inches.|inches.|inches.|inches.|inches.|inches.| inches.
0.13 | 0.13 | 0.13 | 0.12 | — | 0.14 | 0.025
-------+-------+-------+-------+-------+-------+-----------

[Sidenote: 83]]