The shooting powers of gun barrels are dependent on two circumstances--goodness of metal, and a proper shape of exterior: it cannot be too often repeated, _that a gun barrel is a spring_, to all intents and purposes; if you add metal, you add stubbornness, and destroy that expansibility, without the existence of which the barrel is, comparatively speaking, useless. Heavy, ponderous barrels do not propel a charge of shot with either that smartness or degree of closeness that a barrel more scientifically constructed does; you have less recoil certainly, but the addition of half an inch of more metal behind the butt of the breech would do this more effectually, and save you carrying an additional weight. The gradual ignition of powder obviates the necessity of a great thickness of metal in the sides of the barrels; but if it is determined to persevere in the use of peculiarly fine grained powder, you would certainly be justified, nay, required, to have more and better metal than at present, for the electrical nature of the explosion will throw upon the tube that force which would be more judiciously employed in giving impetus to the charge of projectiles. I have found that expansion will increase the shooting powers of a barrel; but then it must not be the expansion of an unelastic piece of metal, but of metal whose elasticity rebounds with a force equal to that with which it expands; for whatever else you may obtain by creating friction, by boring the breech end of the barrel wider you obtain a greater expansion, as it no doubt has that tendency. We find it an invariable fact, that when barrels are very heavy, compared with their size of bore (if a cylinder), they shoot weak. Also, when barrels are made of irons of different temperatures, where one is placed to prevent the expansion or springing nature of the other, they are never found to shoot well. As a proof of this fact, let any one take the best barrel he ever shot with, and encase it with lead very tight; fire it at a dozen sheets of paper, and see if the effect be equal to what it was when the barrel was unencumbered. On the contrary, it will be found to have shot very weak, though close. Let him then examine the lead; and, if any moderate substance, he will find that the explosion has enlarged it considerably. This experiment I have tried repeatedly, and can vouch for its truth. The proof of barrels is another fact corroborating the truth of our assertion. What else can occasion the bulging, but the expansion? Where the barrels are possessed of soft and hard portions (which is the result of different tempers of different metals), one expands further than the other, and then, of course, the soft part receives no assistance from the hard, and it does not return to its original state.