The stock, which came in bars of mill length, was cut off so as to make a barrel with the proper allowances for trimming (Fig. 21). They then pass to the forging or upsetting press in the adjoining room. This press, which is shown in more detail in Fig. 22, handled the barrels from all the heating furnaces shown. The men changed work at frequent intervals, to avoid excessive fatigue. [Illustration: FIG. 23.--Continuous heating furnace.] Then the barrels were reheated in the continuous furnace, shown in Fig. 23, and straightened before being tested. The barrels were next tested for straightness. After the heat-treating, the ends are ground, a spot ground on the enlarged end and each barrel tested on a Brinell machine. The pressure used is 3,000 kg., or 6,614 lb., on a 10-millimeter ball, which is standard. Hardness of 240 was desired. The heat-treating of the rifle blanks covered four separate operations: (1) Heating and soaking the steel above the critical temperature and quenching in oil to harden the steel through to the center; (2) reheating for drawing of temper for the purpose of meeting the physical specifications; (3) reheating to meet the machine ability test for production purposes; and (4) reheating to straighten the blanks while hot. A short explanation of the necessity for the many heats may be interesting. For the first heat, the blanks were slowly brought to the required heat, which is about 150 deg.F. above the critical temperature. They are then soaked at a high heat for about 1 hr. before quenching. The purpose of this treatment is to eliminate any rolling or heat stresses that might be in the bars from mill operations; also to insure a thorough even heat through a cross-section of the steel. This heat also causes blanks with seams or slight flaws to open up in quenching, making detection of defective blanks very easy. The quenching oil was kept at a constant temperature of 100 deg.F., to avoid subjecting the steel to shocks, thereby causing surface cracks. The drawing of temper was the most critical operation and was kept within a 10 deg. fluctuation. The degree of heat necessary depends entirely on the analysis of the steel, there being a certain variation in the different heats of steel as received from the mill. MACHINEABILITY Reheating for machine ability was done at 100 deg. less than the drawing temperature, but the time of soaking is more than double. After both drawing and reheating, the blanks were buried in lime where they remain, out of contact with the air, until their temperature had dropped to that of the workroom. For straightening, the barrels were heated to from 900 to 1,000 deg.F. in an automatic furnace 25 ft. long, this operation taking about 2 hr. The purpose of hot straightening was to prevent any stresses being put into the blanks, so that after rough-turning, drilling or rifling operations they would not have a tendency to spring back to shape as left by the quenching bath.