While the second operator grasps the legs of the barrel rest, quite near the barrel, No. 1 separates the barrel from the receiver by drawing the latter to the rear. Resting the butt on the ground No. 1 now mounts the fresh barrel and pushes it home. Meanwhile No. 2 handles the hot barrel by means of the barrel rest, which he then detaches as follows:— (_a_) Fold the legs. (_b_) Turn the legs forward until in line with the barrel. (_c_) Pivot the legs half a turn around the lug of the front sight carrier, thus permitting the separation. The fresh barrel being mounted, No. 2 attaches the barrel rest and resets it. A hot barrel may be carried by means of dismounting wrench. COOLING BARREL. To reduce wear of rifling, the barrel should be kept cool if circumstances allow. Water is not harmful, and when available may be copiously applied to barrel by means of a sponge or rag. A hot barrel may be dipped in water, but all traces of latter must be removed from barrel bore and gas cylinder, by blowing through same, by means of cleaning rod, or by firing two or three loose cartridges. Until all water is blown out of gas cylinder, the gas pressure may be insufficient for ensuring automatic action. USE OF THE REGULATOR. In order that the working of the gun may be regular, sufficient power must be available to ensure complete recoil of the piston. The amount of power necessary must vary because of insufficient oiling, dust, or fouling in the mechanism, &c. Then, again, pressure of the powder gases may vary because of temperature, deteriorated powder, or badly worn rifling. The regulator affords means of varying the power which works the gun. Under normal conditions it should be set at 25. To test the automatic action, fire several shots with regulator set at 25 and cocking handle at “R,” and observe:— (_a_) One shot should be fired at each pull of trigger. If more than one shot is fired at a time, it shows that piston does not recoil sufficiently after each shot to catch on sear. (_b_) Claw of pawl should catch in the opening in strip at each shot. If pawl rides on top of strip instead of catching, it shows that piston does not recoil sufficiently to throw feed lever through a complete stroke. (_c_) The ejection should be regular and energetic. If these three points are not satisfactory it may be concluded that there is a lack of power, and regulator should be screwed up from 5 to 10 divisions. On the other hand, too much power is not desirable, as the vibration due to the violent action of the mechanism necessarily affects accuracy. ACCIDENTAL STOPPAGES IN THE AUTOMATIC ACTION OF THE GUN. In case of a jam always proceed as follows:— (_a_) Open breech completely by means of cocking handle.