"How much of a charge do you put to each barrel?" he asked; and when the formula was given him for each of the different styles of rifle, the boy whistled in amazement.
"I should think that any barrels that stood that test could stand anything afterwards," he said admiringly.
"Well, they do," the other said. "It's very seldom that you hear of a first-class gun exploding. I don't recall a case of one of ours for years and years. And even if by some chance flaw they did, the good ones, being nickel steel, would just make a hole in the barrel,—not fly to pieces. But, as a matter of fact, any barrel that has been through that 'proof-room' will have been subjected to the greatest strain it will ever have to undergo, for there is no cartridge made that would have one-half the power in proportion to the size of the barrel."
From the proof-room Hamilton's guide led him through different parts of the works, where various machines were employed in preparing and finishing the rough forgings he had seen made and annealed. Thus, for example, in a receiver for a gun stock, one machine worked a bevel edge on it, another bored it to the size of the gun barrel, accurate to the thousandth part of an inch, another pierced the tiny screw holes, and yet other machines made even the minute screw, done, as was explained to Hamilton, so that the threads in each should fit with absolute exactness.
"But do you really mean to say," queried Hamilton in surprise, "that every one of these fifty or more parts of each gun is inspected and tested?"
The official led him to a number of long rows of tables.
"Here," he said, "are girls doing nothing else all day long. Here is a testing die for a part of the ejector of one of our 1911 models. You see that there are two spaces for all of them. It must fit into this one, it must not fit into that, which is a thousandth of an inch smaller. If too big, you see it won't fit into either, if too small, it would fit into the one where it ought not. Every tiny piece is gauged on all its sides and in every hole and at all points with this double gauge system."
"That doesn't leave much for guesswork," said Hamilton. "But there is something that's been puzzling me."
"What is that?" asked his guide.
"I've always heard a lot about gun-metal," Hamilton answered, "and yet all the way through, these parts have been nothing but steel. And all the guns I ever saw had that bluish look, as gun-metal has. For example, my watch is what they call gun-metal," and he took it from his pocket and showed the back of it.