The back-sight is screwed into the top of the stock, 3 in. behind the
catch for the bow-string. It is an ordinary peep-sight, fig. 156, p. 217.
To Aim the Crossbow
In sighting the crossbow, be careful never to raise the sliding bar
of the fore-sight more than 1/2 in. above the surface of the metal beneath
it, or the bolt is likely to strike the bar and smash it.
The height of the sliding bar need seldom be more than about 1/4 in.,
II, fig 153. previous page.
When the crossbow is discharged, its bolt is intended to pass close
above the sighting bead on the centre of the sliding bar of the fore-sight.
The stock of the crossbow being sloped downwards to its fore-end, enables
the bolt to leave the stock so that it passes above the bar of the fore-sight.
The dotted line, A-B, fig. 147, p. 208, shows the flight of the bolt as
it leaves the crossbow.
If the bolt passed under the sliding bar, the bar would require to be
so high above the stock to avoid contact with the bolt, that the latter
would strike much below the mark at 40 yards, whatever the aim taken.
The groove for the bolt runs out to nothing from the part of the crossbow
where its stock begins to slope downwards, and this part is 1 ft. 3 in.
from its fore-end.
This arrangement of the groove (copied from weapons of mediaeval days),
causes the bolt to start off with a free and true flight, as it encounters
no friction to divert its direction on quitting the stock of the crossbow.
When you have sighted the crossbow so that it will place eight out of
twelve bolts in the gold of an archery target, at 50 yards distance, you
may fix its fore-sight beyond movement, and stop up with beeswax all the
peepholes of the back-sight, except that which you find is the correct
one to aim through.
If when sighting the crossbow at a mark, you find it sends its bolt
too much to the right, you will have to move the sliding bar to the right
till the bolt attains a straight course. If the bolt inclines to the left,
then the bar must be moved to the left.
The principle of sighting this weapon is identical with that of the
bullet crossbow (pp. 198, 199). The bead on the sliding bar, as seen through
the peep-sight, gives the alignment for a correct aim.