TM 9-1275

a. Operating Rod Modification. (1) The operating rod modification provides a radius at the corner in the operating rod near the operating rod catch notches (fig. 49) to prevent the development of a crack in this section.

(2) Use a 3/16-inch end mill of conventional design in performing this modification.
(3) Mount the operating rod on the table of the milling machine with the flat section, on which the drawing number is stamped, perpendicular to the axis of the cutter. Ascertain starting point of cut with scribe line on improvised depth gage. (See fig. 20) Start the cut at the rear end and travel forward on rod until the specified radius is produced.

Note. It is essential that the marks of the cutter be lengthwise with the rod rather than perpendicular to it, as any mark running perpendicular will localize stress and form a starting point for fatigue cracks.

Do not use any method of machining that will make scratches or machining marks perpendicular  to the rod. Be careful not to remove more material than that specified in the drawing. (See fig. 49)

(4) Use the improvised height and depth gages (figs 19 and 20) to check cut. The gage shown in figure 50 is a maximum-minimum gage to check depth of cut in the handle section of the operating rod. The gage shown in figure 51 is a maximum-minimum gage to check forward travel of the cutter, starting point of the cut. With the gage in position on the rod, origin of cut should fall within width of solid line scribed on gage.
b. Refinishing Shiny Gas Cylinders. Rifles with shiny gas cylinders must not accompany troops to overseas bases. The gas cylinders, gas cylinder locks, and gas cylinder lock screws of these weapons are machined from stainless steel. Normal methods of blackening these components, such as penetrating (application of black finishing oxidizing material) or parkerizing, are ineffective; therefore, if no special processes are available (see TM 9-1861), refinishing of the gas cylinders must be performed by painting, using the following procedure:

(1) Remove all old paint, and make certain the surfaces of the parts to be painted are free from grease or other foreign matter.
(2) Assemble the gas cylinder lock to the gas cylinder, securing it with the gas cylinder lock screw.
(3) Paint shiny parts with a mixture of flat black paint thinned with synthetic enamel thinner in the ratio of 2 ounces of thinner to 1 quart of paint. Both are listed in ORD 3 SNL K-L and may be requisitioned from Raritan and Benicia Arsenals. The paint may be obtained in quart cans; 1 quart will paint approximately 250 gas cylinders. The thinner may be obtained in 1/2-pint cans; 1/2 pint is enough for approximately 1 gallon of paint. Have some additional thinner on hand to clean the paint brushes or spray guns, and for thinning old paint. Be certain that the paint and thinner are mixed thoroughly, then apply with a spray gun or small, flat paint brush. Take care to prevent paint from running into the bore of the gas cylinder.
(4) Place the painted assembly in an oven (fig. 52), and bake for 1 1/2 hours at a temperature of 300° F. to 350° F. To prevent drying or charring soft materials, the heat is not to be greater than the maximum temperature prescribed. The baking may be accomplished in any type of improvised oven and in conjunction with any available source of heat capable of producing a relatively low temperature of 300°F. An oven for baking purposes can be improvised from sheet iron; or, if this is impossible, an ordinary domestic-type, kerosene stove oven may be used. The oven may be heated electrically, by gasoline, or by oil, and may be used in conjunction with a field range or portable stove.

Caution: Care must be used to prevent the parts from being subjected to direct or open flame.

(5) When properly applied, the resultant dead-black finish which does not reflect light will be hard, durable, unaffected by the normal heat of the weapon, and highly resistant to abrasion. This method may also be used to blacken other nonfunctioning exterior surfaces, such as folding metallic stocks, butt plates, front sights, sling swivels, and other small parts.
c. Barrel Replacement. (1) Disassembling. Separate the unserviceable barrel from the receiver, as described in paragraph 19b.
(2) Assembling. Without using undue force, screw barrel on receiver by hand until it fits tightly. The receiver should be approximately 15° out of its correct position on the barrel to insure a tight fit when the final draw is made in the barrel and receiver assembly fixture. Clamp the group in the barrel and receiver assembly fixture with three clamps, tightening the lower clamp first to level the receiver. (See fig. 53) Slide key, located on the indicating arm of the fixture, into the upper gas cylinder spline cut as far as it will go. Pull on the lever, thereby turning the barrel the required distance to bring the indicator to agreement with the qualifying line on the fixture.

Note. Pointer must travel the distance from within lower space cut to qualifying line cut (fig. 53) to insure a tight fit.

Then loosen the locking clamps and remove the assembly from the fixture, using a bar placed through the trigger housing opening in the receiver as a lever to start the assembly from the fixture.
(3) Checking barrel and receiver assembly fixture. Check the barrel and receiver assembly fixture (fig. 13) monthly or oftener if necessary to see that barrels are being aligned properly. To make a check, use a barrel and receiver that has been assembled in the fixture and slip the barrel aligning gage with pin (fig. 9) over the splined portion of the barrel. (See fig. 54) For this test select a barrel which allows no sideways play of the gage in the spline cut. Insert a 3/8-inch rod through the rear sight pinion holes and suspend the receiver on a pair of parallels or V-blocks just high enough to clear surface of plate. Elevate the muzzle to a level position and block up. Levelness can be found by using the dial indicator on top surface of the gage in the direction of the center line of barrel. Now using the dial indicator, gage the top surface of the barrel aligning gage on the end of the muzzle. If the top surface of the barrel aligning gage is parallel to the surface plate, the alignment of the barrel and receiver is correct.

Note. A properly aligned barrel should be plus/minus 0° 20 minutes (plus/minus ,0058 inch on top surface of barrel aligning gage) to the horizontal plane of the receiver. (See fig. 55)

(4) Looseness of barrel in receiver. If the barrel screws into receiver by hand to within 7° of its assembled position, it is considered to have "light draw". This may be corrected by placing barrel and receiver in the assembling fixture and assembling properly. Remove it from the fixture and chuck barrel in a lathe, with the receiver being as close to the chuck as possible. Allow room for the swaging roll. (See fig. 18) With the roller in tool post, roll the barrel, (See fig. 56) The edge of the roller should be 1/4 inch away from the receiver. Do not loosen the barrel after rolling, as rerolling will be necessary.
d. Headspace reaming. (1) Wipe the chamber thoroughly with a cotton flannel patch before and after each reaming. Screw the short adapter (fig. 11) deeply into the reamer and tighten lock nut. Dip the reamer in lard oil and insert it into the reamer guide. Make certain bolt lug recesses in receiver and bolt lugs on reamer guide are free from dirt and foreign matter. Place the guide and reamer in the receiver (fig. 57) and tighten thumb screw to hold guide in position.
(2) Attach the universal-jointed extension to the reamer and rotate it with a chuck.

Note. If the reamer has been correctly assembled to the adapter it will not cut, but will be held away from the chamber by interference between a shoulder in the guide and the adapter.

Unscrew the adapter from the reamer a little at a time until the reamer begins to cut. Adjusting of the headspace reamer is accomplished by loosening the locking nuts and backing off or advancing the adjusting screw a little at a time, using the field test bolt (fig. 7) and headspace gage named in the serviceability chart (fig. 23) to check for proper adjustment.

(3) When the adapter is correctly adjusted in the reamer, check the tightness of the locking nut. The reamer, once it is adjusted, and if carefully used, will continue to ream to the same dimension until the reamer becomes dull and must be replaced or resharpened.

Note. Any reaming beyond the minimum limit of 1.940 inches reams away a part of the headspace life of the assembly; therefore, make certain all reaming is held to as near the minimum possible.

Never turn the reamer backward, as such action will chip the lands. Use liberal quantities of lard oil when reaming and wash all chips from the reamer with lard oil each time it is removed from the work. Sharpening stones are furnished for the purpose of keeping the reamers honed properly. Proof fire every rebarreled rifle.

23. Assembly

a. General. (1) Assemble in accordance with instructions contained in FM 23-5.

(2) Assembly of parts covered in the following paragraphs is performed only by ordnance personnel and therefore not covered in FM 23-5.
(3) Methods used by fifth echelon organizations for assembling parts in mass rebuild are also covered in the following paragraphs.

b. Follower And Slide Assembly. To assemble, hook the slide in place in the small end of the follower. Stand the two pieces on end (fig. 58) or mount them at an angle in a vise. With a soft hammer deliver a sharp blow on the rear end of the slide. It will snap back into position on the follower.
c. Assembling Barrel To Receiver. Refer to paragraph 22c for assembly of barrel to receiver.
d. Bolt Assembly. The use of the bolt assembling fixture (fig. 13) is the easiest method of installing the extractor (fig. 59) when a large number of bolts are being repaired. Install firing pin, extractor spring, and extractor plunger, also ejector spring and ejector in bolt and clamp bolt in extractor assembling fixture. Start extractor in bolt and tap in place with a soft hammer.

Note. This fixture can also be used to remove the extractor.

e. Assembling Ejector, Extractor, and Rear Sight Springs. When rebuilding large quantities of rifles, fifth echelon organizations will find the ejector assembling fixture (fig. 13) a useful tool for assembling the ejector, extractor, and rear sight springs to their respective components. To use, select select the proper spindle  and bushing corresponding to the components being assembled. Place the spring in the aperture in the spindle and its related component in the bushing. (See fig. 60) Press forward on knob until component is inserted in spring.
f. Assembling Rear Sight. When assembling or disassembling large quantities of rear sights, use the windage screw knob wrench. (See fig. 12) Fit the adjustable split socket over the windage or elevating knob and tighten thumb screw. Use crank to facilitate rotating of the rear sight knobs.

TM 9-1275