But in this view he is in a minority. Whereas the invention of helical grooving is generally attributed to Augustin Kutter, a gunmaker of Nuremburg who died in A.D. 1630, straight grooving had been known since 1480, and is ascribed to one Gaspard Zöllner, a gunmaker of Vienna. “Smooth-bore guns,” says Schmidt,[113] “had the disadvantage of fouling, and with the poor powder could only be recharged by leaving a comparatively large space between the ball and the barrel. This windage prejudiced straight shooting. To overcome this deficiency the practice was adopted of cutting grooves, more or less numerous, in the barrel, and in wrapping the ball in a rag greased with suet. In this way the windage was reduced, and as the greased rag cleaned the barrel, the weapon could be recharged for a large number of rounds. At first these grooves were made straight.”
A theory propounded in a well-known treatise published in the year 1808, entitled Scloppetaria, was to the effect that grooving had its origin in the habit which the early huntsman had of gnawing or biting the balls before putting them into the piece, with a view to causing the wound inflicted by them to be rendered more severe. This habit gave rise to the idea that the barrel itself might be made to do the work of jagging or indenting the bullet. “These grooved or sulcated barrels appear to be of great antiquity, and are said to have existed in Russia long before their introduction among the civilized nations of the south.”
According to Hans Busk, straight grooving was adopted for the reason given by Schmidt: i.e., purely for the purpose of facilitating loading, and for assisting to dislodge the products of combustion left in the bore. “No doubt the adoption of this plan was calculated to increase the efficiency and accuracy of the arm from the steadiness it imparted to the bullet in its passage through the barrel.”
And that is a view which, it is suggested, might be expanded to give a motive or combination of motives which may well have operated to induce the early gunmakers to cut grooves in their musket-barrels. Thus: the variations in the flight of spherical lead balls fired from smooth-bore guns were chiefly due (though these causes were not clearly appreciated till a much later date) to the incalculable effect of windage and to the varying axis about which spin took place. If by any means windage could be reduced, and if the ball could be made to assume a central position in the bore and spin about a definite axis in its flight, a large increase in accuracy would be attained. Suppose, for instance, a single groove or gutter were filed along the barrel parallel with its axis. The effect surely would be, by creating a rush of powder-gases along this groove, to cause the ball, under the tangential impulse of the gases, to rotate always in the same plane as it passed through the bore. And thus by the cutting of this single groove a uniformity of flight of the ball would be attained which was unattainable without the groove. The same effect, in fact, was produced by Robins when he bent the musket barrel. He demonstrated that the result was to make the ball roll on a definite part of the barrel and thus to deviate during flight in a definite direction. He might have shewn, as another result of his experiment, that by giving the ball a uniform spin he had endowed it with a regularity of flight, or accuracy, many times greater than it before possessed.
Or suppose that, instead of one groove, two or more grooves were filed in the same way. While the above advantage derived from the single groove would be less fully obtained, another would result. By providing a space on each side into which fouling might spread, and into which the plastic metal of the ball might be intruded by the pressure of the ramrod, their presence would certainly allow of a tight-fitting ball being used. The loss in efficiency of discharge due to friction between ball and barrel would be more than compensated for by the annihilation of windage.[114]
Suppose, however, that the grooves were augmented in number until they became a series of triangular serrations all round the interior of the barrel. The value of this formation might lie, not so much in the grooves, as in the ends or points of the serrations which supported the ball and held it in a central position on the true axis of the gun. In short, the prime idea of the gunmaker may have been, not so much the provision of grooves, as the provision of internal ribs for holding the ball truly in the musket.
Whatever the cause or motive which led to its adoption, the rifling of musket barrels became a common practice in the sixteenth century. Two significant quotations will suffice to show the period of the invention. The first is an edict issued by the Swiss Government in 1563:
“For the last few years the art of cutting grooves in the chambers of the guns has been introduced with the object of increasing the accuracy of fire; the disadvantage resulting therefrom to the common marksmen has sown discord among them. In ordinary shooting matches marksmen are therefore forbidden under a penalty of £10 to provide themselves with rifled arms. Everyone is nevertheless permitted to rifle his military weapon and to compete with marksmen armed with similar weapons for special prizes.”[115]
The second is a recipe from a book by Sir Hugh Plat, written in 1594.
“How to make a pistol whose barrel is two feet in length to deliver a bullet point blank at eight score. A pistol of the aforesaid length and being of petronel bore, or a bore higher, having eight gutters somewhat deep in the inside of the barrel, and the bullet a thought bigger than the bore, and is rammed in at the first three or four inches at the least, and after driven down with the skowring-stick, will deliver his bullet at such distance.”