be deep enough to allow the extractor to come down into the cannelure, so that minimum cartridge will snap in and be held up firmly in place. Faulty ejection may result if the cartridge is allowed to drop even a short distance. To test this, remove the bolt and firing pin and insert a live cartridge under the extractor. It should be able to withstand considerable shaking without dropping down out of place. Examine to see if the extractor hook bears against the bottom of the cannelure at all points and that the base of the cartridge is held snugly against the face of the bolt. About 0.01 inch clearance between the base of the cartridge and the bolt face will not in general affect the operation of the rifle, but more than this may cause weak ejection. The lower corner of the extractor and lips of the bolt should be slightly rounded so as not to chip brass from the cartridges as they slip up into place. The rear face of the notch in the extractor, which bears against the lug of the bolt during extraction, should be slightly undercut, thus tending to prevent the extractor from slipping over the rim of the cartridge or from pulling out. The rear face of the extractor hook should be square and the extracting edges fairly sharp. An excessive amount of dirt under the extractor may result in failure to extract or failure to eject. The extractor should be a snug fit in the bolt. Side play or twisting is especially liable to cause trouble. Worn or defective extractors may often be corrected by proper and careful filing. The extractor spring rarely causes any trouble.

e. Trigger guard mechanism.-(1) The fit of the trigger guard in the receiver is not important except that it should be fairly snug sideways. The sear should be a loose fit in the sear carrier. The nose of the sear, as well as the sear notch in the slide, should be correct in shape in order to maintain positive engagement. The sear pin should carry the tension of the counterrecoil spring, leaving the trigger pin free. The trigger should be a loose fit in the trigger guard and the connector loose in the trigger. The trigger pull should be smooth and from 6 to 10 pounds. The change lever should work smoothly. The ideal condition in semiautomatic fire is for the cam on the connector to engage the sear carrier just at the moment the sear releases the slide. The sear spring should fit in the trigger guard without an excessive amount of slide play. The center leaf should have a smooth and continuous bearing against the bevel surface of the connector. The magazine catch should work freely and easily and should hold the magazine up closely to the bolt supports.

(2) The ejector should fit fairly close in the trigger-guard guides. An excessive amount of play forward and backward may result in weak ejection. This can sometimes be corrected by bending the ejector slightly. The upper end of the ejector should spring slightly when pressed back. The location of the working end of the ejector for height and side position is of primary importance. To examine this, draw back the mechanism until the bolt face is even with the ejector. The ejector should fit up within 1/32 inch of the bolt but should not bind. A poor fitting ejector can be corrected by bending until it fits up closely in the notch of the bolt. The upper part of the ejector should not bend rearward. If the ejection is correct the shells will be given a spinning motion as they leave the rifle and will be thrown diagonally forward with considerable force. Test the ejection with a magazine filled with dummies. First operate the rifle slowly by hand, which should result in positive ejection. Then operate rapidly, when the cartridge should be ejected with force.

f. Rear Sight.-If the rear sight is properly assembled with a good driving fit it will give little trouble. If the sight works loose from the receiver it may be necessary to replace the sight base. It may, however, be possible to swell the dovetail of the rear sight base by light and careful peening with a hammer until the necessary drive fit is obtained.

g. Buffer assembly.—If properly assembled the buffer tube assembly will cause little or no difficulty. Special attention should be given to see that the buffer spring is always assembled behind the buffer friction cups and cones. The bronze buffer friction cups sometimes split and in this case should be replaced.

h. Magazines.—Magazines should fit easily in the receiver and should be free enough to drop out under their own weight when the magazine release is compressed. The form of the inturned lips is important. Cartridges should strip out smoothly and without excessive friction, which might hold back the bolt to such an extent as to cause failure to breech and misfires. The inside distance between the pressed-in ribs should be maintained within reasonable limits. The magazine follower should work freely. Deformed or battered magazines may be repaired by placing over the salvaging tools and bringing back into shape with a lead hammer.

38. Automatic rifle inspection.--Careful and frequent inspections should be made of the following:

a. Receiver and barrel.

(1) Tightness of flash hider and front sight.

(2) Condition of bore.

(3) Tightness and alignment of barrel.

(4) Burrs on receiver or any part.

(5) Position of bolt guide and spring.

(6) Tightness of buffer tube.

(7) Tightness of stock.

b. Rear sight.

(1) Firmness of rear-sight base.

(2) Free movement of slide.

(3) Condition of slide catch spring.

c. Gas cylinder and tube.

(1) Proper alignment of gas ports.

(2) Fouling of gas cylinder.

(3) Burrs.

d. Gas piston and slide.

(1) Fouling of piston.

(2) Sear notch for ships and burrs.

(3) Hammer pin for looseness. (Should be loose.)

(4) Length of recoil spring. (15 inches.)

e. Bolt group.

(1) Proper fitting of extractor.

(2) Security of bolt lock pin.

(3) Clearance for firing pin in face of bolt.

(4) Bolt and bolt lock for wear and burrs.

(5) Shoulder of firing pin to see that it is cammed easily and in alignment,

by cutout portion on underside of bolt lock.

SHOWING FURTHER MOTION OF RECOILING PORTIONS TO REAR AND EXTRACTION
OF CARTRIDGE CASE

f. Trigger guard group.

(1) Length and strength of sear spring.

(2) Wear and burrs on all parts.

(3) Verify presence of all springs.

(4) Worn magazine catch.

h. After rifle is assembled, test for proper assembly and action, especially trigger mechanism, and piston in gas cylinder.