The rifling machine, in its most approved form, consists of a bed carrying a !mad for !wilding and indexing the barrel. and a carriage having a spindle for holding the rifling rod, and all the appliances necessary to control its mo tion and feed the cutters automatically.
The head has a spindle which holds the barrel by means of a convenient chuck, and is provided with an indexing arrangement by which it is automat ically turned at the end of each stroke of the rifling rod through the proper angle to give the required number of grooves.
The carriage has a spindle for holding the rifling rod, on which is a pin ion meshing with a rack on the carriage cross-slide. The carriage is given a reciprocating motion by means of an ordinary open and crossed belt-revers ing mechanism, which is operated by dogs on the carriage at the end of its stroke. The rifling bar controls the twist of the rifling, and is placed above the carriage, and connected with the carriage cross-slide by means of a swiveled slide. It is pivoted at its central point so it can be set at any angle, and as the carriage moves along the bed a transverse motion is imparted to the carriage cross-slide. This causes the spindle to turn as it advances, so that the rifling cutter describes a true helix. If an increasing twist is required, the rifling bar must be formed to suit the curve of the rifling, the ordinates of the curve of the rifling bar being in the same proportion to the ordinates of the devel oped curve of the rifling as the pitch diameter of the spindle pinion is to the bore of the gun.
The rifling rod is provided with one or more cutters, which are fed out by means of a wedge-shaped plunger, which extends beyond the end of the rod, and is driven in at the end of the stroke by an automatic feeding device. This is arranged so that the feed is always alike, whatever the variation in the travel of the carriage, and stops when the cutter has reached the proper depth. The rifling bar being set at the proper angle, and all the dogs and stop nuts being adjusted, the barrel is placed in the head, and the machine started by a lever placed at a point on the bed where the operator can ob serve all the motions of the machine. After starting, the carriage continues its reciprocating motion, the head indexes the barrel at the end of each stroke, and the cutters are fed until the grooves have reached the proper depth, when the feed stops, the machins is stopped by the operator, and a fresh barrel is put in place.
This machine is designed to take gun barrels of any size up to forty-five caliber and thirty-six inches long. The regular machine is arranged for four, five and six grooves of uniform twist, from straight to one turn in five inches, either right or left hand, but can be built for any number of grooves, and for an increasing twist of any desired curve. The cutting speed for ordi
nary steel is thirty feet per minute, and is uniform throughout the stroke. The larger machines differ somewhat from this machine; the indexing arrangement being operated by hand, The Pope system of rifling, noted for its excellency, has eight wide grooves, which are on a radius about three times the radius of the bore, and has the corners rounded out, so dirt is easier removed, and it is cleaner in use. This groove is cut just deep enough to clean the bore in the centre and give a depth at the corners of about .00.r. The lands are very narrow (about one-fifth to one-sixth the groove). The bullet is made with a base large enough to fill the grooves completely, and the body of practically the same diameter as the bore. This gives a form that is gas tight, loads Nery easily. (being assisted in this by the narrow lands and choke bore) and on upset, instead of the body- of bullet meeting only sharp lands and these cutting into the body more or less unequally, it is immediately held to place by the nearly flat centre of the broad grooves, and swells out into grooves equally and perfectly central; consequently it is accurate. In this system a false muz zle and starter are used, and the lubricated bullet seated from the muzzle, the shell with powder being afterward inserted in the ordinary way. In doing this the labor is very light, as the shooter has to handle nothing over a few ounces weight, the rifle standing in the loading stand. By the simple act of pushing the bullet home the sharp, flzt base of the bullet cuts the dirt down behind it, and does so exactly alike, each time giving- a uniformly clean bar rel without the labor of cleaning. The result of these things is that we attain all the accuracy of patched bullets, an I in ordinary hands more, without the labor of cleaning. This is also less labor than the ordinary' way of seating a greased bullet in the breech, having to invert the rifle and generally sustain ing its weight while so doing. Other things being equal, the man who tires himself least does the best shooting i the long run, and if this is accompa nied by increased accuracy of the rifle, he has a great advantage over his fel lows who do otherwise. A properly mule barrel, loaded in this way, will shoot to shot groups at 2oo yards that will average about 1-4 or t 1-2 inches less diameter than the same or an equally good barrel shot dirty, bullet seated from the breech.