Without finding fault with low-price rifles that " do the work " remarkably well, let us consider the points of a thoroughly well made rifle which can be turned out at a higher, but still reasonable, cost.
First, the barrel, which is by all odds, the most important part of the gun. In the day of black gunpowder our best rifle barrels were made from mild steel that was so soft it could fairly be cut with a knife. Such metal was so easy to machine that good barrels could be turned out very rapidly and with little hand finishing; hence they were cheap, but shot as accurately as any. Smokeless powder required stronger material, and j acketed bullets required harder metal. This was supplied by the commercial nickle-steel of our day, harder to work than the soft steel it replaced, but still capable of being turned out in much the same way. Common nickle-steel will do for cartridges of the " medium game" class mentioned in a previous chapter; but when it is employed with ammunition of the " big game " or military class, there is trouble.
The trouble comes from erosion of the rifle bore. It has been assumed by riflemen generally that the erosion that cuts down the " accuracy life" of their barrels to a thousand rounds or so is caused by the excessive friction of jacketed bullets, unlubricated, driven at high speed through the rifle bore. If this were true, the wear would be fairly uniform throughout the bore, or might be greatest toward the muzzle, where the bullet gets its highest velocity. Such is not the case. Erosion always is greatest immediately in front of the neck of the chamber, where the bullet starts. Instead of being uniform, it begins with slight pits which then are guttered out in irregular channels.
The gutters slowly deepen, and still more slowly creep forward up the bore. By the time they have advanced about two inches beyond the neck of the chamber they have deepened so much that a bullet leaving its cartridge shell has room to tilt before taking the rifling, and is deformed, perhaps has its jacket split, before entering the perfect part of the barrel. This damage is done by the gases of explosion of nitro powder, which are so hot that ordinary steel cannot stand the temperature. At first a little of this gas escapes around the bullet before it has gone far enough to seal the bore, and so the pits form. As the eroded portion extends, more gas escapes ahead, and more guttering results.
A barrel of ordinary nickle-steel will lose accuracy quite perceptibly after 1,000 rounds of the '03 U. S. ammunition (220-grain bullet), or even after 500 rounds, if the barrel happens to be a little above caliber. After, say, 3,000 rounds, it will shoot quite wild, notwithstanding that the forward nine-tenths of the bore may remain virtually intact. Such steel is strong enough to stand the breech pressure, and perhaps hard enough to resist bullet friction, but it will not stand the superheated gases of explosion.
The remedy, in so far as the gun is concerned, is two-fold. First a special compressed steel should be used, or a tungsten-steel, or other alloy that will resist the combined attack of friction and great heat. Second, the barrel should be throated so that the bullet fits as snugly as practicable at the start, and no other fit of bullet should be shot from that barrel. Both the superior steel and the extra work raise the price of the barrel, but the accuracy life of the rifle is greatly lengthened.
Many rifle barrels are soon ruined by excessive scrubbing with chemicals to remove metal fouling. By metal fouling is meant a deposit of hard metal from the bullet's jacket, which sticks with great tenacity, escapes observation for a time, but rapidly accumulates until the rifle shoots wild. Here, as with other diseases, prevention is better than cure. The gunmaker's part is extra care in finishing the interior of the bore, so that it shall be smoothly polished and true to gauge. It is not unlikely that a better material for the bullet jacket may be found than nickled steel, or cupro-nickle-steel—perhaps a bronze of high tensile strength that is a good anti-friction metal as well.
Ordinary lubricants will not work, because they are decomposed (disintegrated into their chemical elements) by the great heat of explosion. Graphite alone will not stick to the bullet. Any inequality of action in a lubricant will make one bullet fly high and another low. Here is room for useful experiment. But in any case the barrel of a rifle that is to use the best modern ammunition should be of high quality and carefully gone over by an expert workman.
The bore of a rifle barrel should not have tight or loose places in it. Either it should be a true cylinder or, preferably, it should have a slight and even taper from breech to muzzle—say a quarter of a thousandth inch greater in front of chamber than at muzzle, in a .30 caliber. It can be tested by carefully pushing a well fitting lead bullet through the bore from breech to muzzle with a steel cleaning rod.
The muzzle is a rifle's most important part, and at the same time the one most exposed to injury by a chance blow or by unskilful use of the cleaning rod. Examine it with a lens. If lands and grooves are not perfectly cut to the very end, or if there be a burr of metal left at the mouth, or any sign of wear, reject the piece at once. Any imperfection here will allow gas to escape unevenly around the base of the emerging bullet and so lilt it at the critical moment of start.
A rifle barrel expands a good deal from the heat of firing, both around the bore and lengthwise. In order that this expansion should be even, the metal should be distributed symmetrically. There is no merit in an octagon or half-octagon barrel; rather the contrary. The best form is round and tapered toward the muzzle.
Every barrel flips or springs more or less at each discharge. So long as this flip is uniform, it may be allowed for in adjusting the sights; but grooves cut into the barrel for attaching sights, or other parts, affect the flip in a way that is detrimental to accuracy. There should be none. Some sporting rifles have a slot for forearm stuck almost directly under the rear sight slot. Such a barrel can be sprung with the two hands.
Some fine rifles have a matted rib extending along the top of the barrel to prevent the glare of sunlight from spoiling one's aim and to cut off the radiation of heat waves that arises from rapid firing. Such a rib, milled from the solid barrel, interferes with uniform expansion and contraction of the barrel, may even buckle it temporarily in continued firing, and the bore departs from a true circle. The difference probably will not be noticed in a sporting rifle, but no rib should be tolerated on an arm for match shooting. The matting is likely in time to aggravate the very trouble it was designed to cure, for when the bluing or browning wears off, as it will do much faster than from a smooth surface, the shooter's eyes will be annoyed by innumerable tiny facets of light.
All friction surfaces of a rifle's action should be polished to a mirror-like smoothness, so that there shall be no sticking, grating, or clattering in operating it. Bolts should be casehardened, small parts finished in a workmanlike manner, and bluing should be put on to stay. If economy must be practised, let it be in non-essentials, and not in the barrel that shoots or the mechanism that controls its shooting.