45 to 0.5 appears to be a fairly satisfactory value, and is
adopted for the present.
Lastly, it may be broadly stated, that with suitable powders, a charge
of one-third the weight of the shot demands for most profitable use a
length of bore equal to about twenty-six calibers; a charge equal to
half the weight of the shot should be accommodated with a bore of about
thirty calibers; while a charge of two-thirds the weight of the shot
will be best suited by a bore thirty-five calibers long. Of course, in
each case, greater length of bore will give increased velocity, but it
will be gained at the expense of additional weight, which can be better
utilized elsewhere in the gun.
The amount of work performed by gunpowder, when exploded in a gun, is a
subject which has engaged a vast quantity of attention, and some highly
ingenious methods of calculating it have been put forward. Owing,
however, to the impossibility of ascertaining how fast the combustion
of large grains and prisms proceeds, a very considerable amount of
experience is required to enable the gunmaker to apply the necessary
corrections to these calculations; but, on the whole, it may be said
that, with a given charge and weight of shot, the muzzle velocity may
now be predicted with some accuracy.
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