Gas check No. 7 (same form as No. 6).-Aluminum bronze gas check. Seat for gas check reamed out so as to increase pitch 0.1 inch on a side. After the 241st round a defect was discovered presenting a honey-combed appearance, through which water percolated; the lip was beveled. During the firing with this check it was necessary to wash and scrape the bearing surface after each round, as well as to clean and wipe the seat with oiled waste. The bearing surface of the gas check was generally smeared with remnants of cartridge bag and powder residue. This check was used from the 222d to the 269th rounds, inclusive; in all, 48 rounds. Of these 48 rounds, in only 14 rounds, or 29 per cent., was the check removed from its seat after firing without difficulty; in the other 71 per cent. of the rounds more or less difficulty was experienced in extracting the gas check. Gas check No. 8.-Aluminum bronze check, with lip beveled- same as No. 7, after the modification made before the 242d round, but a more perfect casting. After round No. 271 incipient cracks were observed over the inner surface of the check, and the gas check was difficult to remove. Two rounds were fired with this check, Nos. 270 and 271. Gas check No. 9 (Plate II, Fig. 6).-New steel gas check, consisting of a steel ring fastened to a steel base by six pins passing through thin steel and copper plates. After the 273d round a piece of sheet tin was inserted in rear of upper side of check. Gas check dismounted after 272d round, and it was found that gas had entered all the joints, though not to any serious extent. This gas check was used from rounds 272 to 281, inclusive; in all, 10 rounds. "In 4 rounds only was it removed without difficulty. Gas check No. 10 (Plate II, Fig. 7).-New gas check; copper cup pinned to steel base and marked "C"; weight, 26 pounds. At the secoud round fired with it the steel was found to be set out, and the pins were loosened. Marks of gas escape. Two rounds fired with this gas check, Nos. 282 and 283. Gas check No. 11-This is the same as No. 9, except that the steel ring is replaced by a copper ring. It was marked "R," and weighs 33.25 pounds. The extractor hooks used to remove the gas check weigh 13 pounds. The check did not produce perfect obturation. It was removed easily except in first two rounds, when but slight difficulty was found in extracting it. This gas check was employed during 29 rounds, from the 284th to the 312th rounds. At the 312th round the gun burst explosively. Plate III, shows the position after rupture of the principal fragments. THE YATES BREECH MECHANISM. This system of breech fermeture consists of: (1) two steel breech clamps; (2) gas check; (3) cam lever; (4) locking device for breech. The steel breech clamps and the gas check are the essential features of the system, and cannot be divorced in its consideration, as without the gas check the clamps are useless and impracticable. The clamps are of steel, and having different degrees of elongation, it is difficult to have them sustain equal pressures at the same time, as one may yield more than the other. The gas check is unattached to the mechanism, which of itself is au objectionable feature, as it requires removal after each round. In this manipulation it is liable to injury from dropping or striking against objects. Its weight for this gun has varied from 26 to 48.5 pounds. For larger calibers it would necessarily possess greater weight and be more difficult to handle. When subjected to direct or slightly inclined fire, the breech mechanism is exposed all the time to its effect. The latching or locking devices used at first were not sufficient to hold the clamps together in firing. The steel cap put over the tenon cut on the rear end of the clamps after the 16th round was the only successful locking device used on this gun, but it is rejected by the inventor in his letter before cited as not being intended for adoption with his system. RESULTS OF FIRING. 1. Number of rounds fired. The total number of rounds fired was 312. The gun burst explosively at the last or 312th round. The details of the firing will be found in the firing record and table of enlargements appended to this report. Appendix 48, Report of Chief of Ordnance for 1885, page 483 et seq., contains the firing record for the first 16 rounds. 2. Velocities and pressures. The following table records the velocities and pressures taken since the previous report: VELOCITIES AND PRESSURES. [Gun: Eight-inch Yates breech-loading rifle, lined with Nashua (N. H.) steel tube. Projectile: Eightinch Hotchkiss; weight, 181 pounds. Powder: Du Pont's hexagonal E. V. L.; density, 1.750; gran. ulation, 72; charge, 35 pounds. Instruments for velocity: Two Le Boulengé chronographs (mean taken). For pressure: "Crusher gauge.] The following table gives the additional pressures taken, without ob serving the velocities. The pressures and velocities were normal; the maximum pressure of 35,000 pounds per square inch, prescribed for eight converted guns, was only exceeded once, in the 16th round, when it reached 39,775 pounds per square inch. The mean velocity was about 1,500 feet per second. 3. Enlargement of the bore. This is found to be very uniform and not excessive. The gun was not star gauged during the last 55 rounds; it was the intention to star gauge after the 315th round, but the gun burst before that limit was reached. Below is given a table of enlargements at the last star gauging. These enlargements do not take into account the play of the tube, which would diminish them by 0.003 inch. Table showing enlargement of bore after 257 rounds, as shown by star gauge. [Total length of bore, 160 inches; length of rifled portion (original), 135.25 inches; total length of chamber (original), 24.75 inches; length of rifled portion (after 16th round), 133.25 inches; total length of chamber (after 16th round), 26.75 inches; play between tube and casing, 0.003 inch.] 133 8.004 8.031 0.027 132 8. 004 8. 029 0.025 101 8.003 8.010 0.007 0.007 131 8.004 8.026 0.022 99 130 Hence, the time required to fire one round is as follows: Longest time = 4 minutes; shortest time = 1.8 minutes = 1 minute 48 seconds; average time = 2.325 minutes = 2 minutes 19 seconds. *This table does not include cases where gas-check or breech mechanism gave much trouble or caused considerable delay. Number of 1 Escape of gas through axial vent of gas-check not considered in this column. 3 The last 32 rounds fired with gas-check No. 4. 4 The last 41 rounds fired with gas-check No. 5. 6 No remark. 7 With little difficulty. RECAPITULATION. Total number of rounds fired Number of rounds gas-check removed easily. Number of rounds gas-check removed with more or less difficulty. Number of rounds in which rammer had to be used to remove gas-check 312 101 211 312 103 160 Rounds. 33+ 32.4 67.6 51.28 (1) The gun burst explosively at the 312th round. (2) The velocities were normal. (3) The pressures were normal with one exception, in the 16th round, where it reached 39.775 pounds per square inch. (4) The enlargements of the tube were not excessive. (5) The obturation was imperfect. (6) The gas-checks were not satisfactory. (7) The gas check is heavy and detachable. It is difficult to handle, and is liable to serious injury from accidental dropping or striking against objects in rapid firing. OPINION. As before stated, "the steel breech-clamps and the gas-check are the essential features of the system, and cannot be divorced in its consideration, as without the gas-check the clamps are useless and impracticable." The gas-checks presented for this trial were detached from the mechanism, which is clumsy, inconvenient, and objectionable. This arrange. ment requires the removal of the gas-check after each round and exposes |