The recoil of a gun becomes an object of importance only when it is very great, for every piece recoils in some degree when it is discharged. The most frequent cause of an excessive recoil is an inequality in the bore of the barrel ; and by this it will be occasioned even when the inequality is too small to be perceived by the eye. The explanation of this upon mechanical principles, indeed, is not very obvious ; for as it is an invariable law that action and re action are equal to one another, we should be apt to suppose that every time a piece is discharged it should recoil with the whole difference between the velo city of the bullet and that of the inflamed powder. The cause to which too great a recoil in muskets has been usually attributed, is the placing of the touch-hole at some distance from the breech-plug, so that the powder is fired about the middle, or towards its fore part, rather than at its base ; to avoid this, a groove or channel is often made in the breech-plug as deep as the second or third turn of the screw, the touch-bole opening into this channel, and thus firing the powder at its very lowest part. It appears, however, from a number of experiments made upon this subject by M. Le Clere, that it made very little difference with regard to the recoil, whether the touch-hole was close to the breech, or an inch distant from it. The only circumstance to be attended to with respect to its situation, therefore, is, that it be not quite close to the breech plug, as in such a case it is found to be more apt to be choked up than when placed about a quarter of an inch from it. It was formerly supposed, that the longer gun barrels were made the greater would be the distance to which they carried the shot, and that without any limitation. This opinion continued to prevail till near a century ago, when it was first proposed as a doubt whether long barrels carried further than short ones. Mr. Robins informs us, that "if a musket barrel of the common length and bore is fired with a leaden bullet and half its weight of powder, and if the same barrel is afterwards shortened one-half, and fired with the same charge, the velocity of the bullet in this shortened barrel will be about one-sixth less than what it was when the barrel was entire ; and if, instead of shortening the barrel, it is increased to twice its usual length, when it will be near eight feet long, the velocity of the bullet will not be augmented more than one-eighth part ; and the greater the length of the barrel is in proportion to the diameter of the bullet, and the smaller the quantity of powder, the more inconsiderable will these alterations of velocity be From these considerations it appears that the advantages gained by long barrels are by no means equivalent to the disadvantages arising from the weight and incumbrance of using them ; and from a multitude of experiments, it is now apparent that any one may choose what length he pleases without any sensible detriment to the range of the piece. The most approved lengths are from 30 to 36 inches. An opinion has generally prevailed among sportsmen that by some unknown manoeuvre the gunsmith is able to make a piece loaded with small shot, throw the contents so close together, that even at the distance of 40 or 50 paces the whole will be confined within the breadth of a hat. From
such experiments as have been_made on this subject, however, it appears that the closeness or wideness with which a piece throws its shot, is liable to in numerable vitriations from causes which no skill in the gunsmith can possibly reach. So variable are these causes, that there is no possibility of making the same piece throw its shot equally close twice successively. In general, how ever the closer the wadding is the better disposed the shot seems to be to fall within a small compass. In firing with small shot a curious circumstance sometimes occurs, viz. that the grains, instead of being equally distributed over the space they strike, are thrown in clusters of 10, 12, 15, or more; whilst several considerable spaces are left without a grain in them. Sometimes one-third or one-half of the charge will be collected into a cluster of this kind; nay, sometimes, though much more rarely, the whole charge will be collected into one mass, so as to pierce a board near an inch thick at the distance of 40 or 45 paces. Small barrels are said to be more liable to this clustering than large ones ; and M. de Marolles informs us that this is especially the case when the barrels are new, and likewise when they are fresh washed; though he acknow ledges that it did not always happen with the barrels he employed, even after they were washed. It is probable, therefore, that the closeness of the shot depends on some circumstance relative to the wadding rather than to the mechanism of the barrel.
The lock of the gun, which comes next to be considered, was originally only a cleft piece of iron, moving on a pin fixed in a stock. To this succeeded the wheel lock, so called from a small wheel of solid steel, which being let off by a spring, by its rapid evolutions elicited fire from the flint, and ignited the priming. This was superseded by the snaplance, in which a motion was given to the cock which held the flint, and a movable plate of steel called the frizel, or hammer, was placed vertically above the pan to receive it. A great many improvements in gun locks have been made during the last twenty or thirty years, which have contributed to render this part of the gun admirably efficient. Our space will not permit us to enter into details ; we therefore refer the reader to the periodical works descriptive of patent inventions. The important requi sites in a gun lock are, that the action of the cock be as rapid as possible, and that it should be so placed, that on uncovering the pan the flint may point into the centre of the priming, and as near to it as possible, without touching it ; the main spring should have a smooth and active motion; the hammer spring should be light, and should give a slight resistance to the cock on its striking the steel, which ought to more on a roller.
The stocks of guns have assumed a great variety of forms. Sportsmen's guns, till within these thirty years, were made very crooked in the stock, and no regard was then paid to the balance of the piece ; since that period straight stocks have been universally adopted, and the length of the stock has been accommodated to the stature of the person for whom it is made.